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New submissions

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New submissions for Fri, 22 Jun 18

[1]  arXiv:1806.07890 [pdf, other]
Title: Turbulence-driven thermal and kinetic energy in the atmospheres of hot Jupiters
Comments: 15 pages, 16 figures, submitted to MNRAS; comments are welcome
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We have performed high resolution $3-$dimensional compressible hydrodynamics simulations to investigate the effects of shocks and turbulence on energy transport into hot Jupiter atmospheres, under a variety of shear gradients. We focus on a local atmospheric region to accurately follow the small-scale structures of turbulence and shocks. We find that the effects of turbulence above and below a shear layer are different in scale and magnitude: Below the shear layer, the effects of turbulence on the vertical energy transfer are local, generally $\lesssim2~\times(\text{scale height})$. However, turbulence can have a spatially and thermally-large influence on almost the entire region above the shear layer. We also find that shock formation is local and transient. Once the atmosphere becomes steady, the time-averaged heat energy flux at $P\sim 1$ bar is insignificant, on the order of 0.001\% of the incoming stellar flux with a shear motion at $P\sim 1$ mbar, and 0.1\% with a deeper shear layer at $P\sim 100$ mbar. Accordingly, the diffusion coefficient is higher for the deeper shear layer. Therefore, our results suggest that turbulence near less dense regions ($P\sim 1$ mbar) does not cause a sufficiently deep and large penetration of thermal energy to account for radius inflation in hot Jupiters, regardless of how violent the turbulence is. However, as the shear layer gets deeper, heat energy transfer becomes more effective throughout the atmosphere (upwards and downwards) due to a larger kinetic energy budget. Therefore, it is more important how deep turbulence occurs in the atmosphere, than how unstable the atmosphere is for effective energy transfer.

[2]  arXiv:1806.07891 [pdf, other]
Title: The Suppression of Star Formation on the Smallest Scales: What Role Does Environment Play?
Comments: 9 pages, 6 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The predominantly ancient stellar populations observed in the lowest-mass galaxies (i.e. ultra-faint dwarfs) suggest that their star formation was suppressed (or "quenched") by reionization. Most of the well-studied ultra-faint dwarfs, however, are within the central half of the Milky Way dark matter halo, such that they are consistent with a population that was accreted at early times and thus potentially quenched via environmental processes. To study the potential role of environment in suppressing star formation on the smallest scales, we utilize the Exploring the Local Volume in Simulations (ELVIS) suite of $N$-body simulations to constrain the distribution of infall times for low-mass subhalos likely to host the ultra-faint population. For the ultra-faint satellites of the Milky Way with star-formation histories inferred from $Hubble~Space~Telescope$ imaging, we find that environment is highly unlikely to play a dominant role in quenching their star formation. Even when including the potential effects of pre-processing, there is a $\lesssim 1\%$ probability that environmental processes quenched all of the known ultra-faint dwarfs early enough to explain their observed star-formation histories. Instead, we argue for a mass floor in the effectiveness of satellite quenching at roughly $M_{\star} \sim 10^{5}~M_{\odot}$, below which star formation in surviving galaxies is globally suppressed by reionization. We predict a large population of quenched ultra-faint dwarfs in the local field, with as many as $\sim 200$ to be discovered by future wide-field imaging surveys.

[3]  arXiv:1806.07892 [pdf, other]
Title: Teetering Stars: Resonant Excitation of Stellar Obliquities by Hot and Warm Jupiters with External Companions
Comments: 14 pages, 9 figures, submitted to MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Stellar spin-orbit misalignments (obliquities) in hot Jupiter systems have been extensively probed. Such obliquities may reveal clues about hot Jupiter dynamical and migration histories. Common explanations for generating obliquities include high-eccentricity migration and primordial disk misalignment. This paper investigates another mechanism for producing stellar spin-orbit misalignments in systems hosting a close-in giant planet with an external, modestly inclined companion. Spin-orbit misalignment may be excited due to a secular resonance, occurring when the precession rate of the stellar spin axis (driven by the inner planet) becomes comparable to the nodal precession rate of the inner planet (driven by the companion). Due to the spin-down of the host star via magnetic braking, this resonance may be achieved at some point during the star's main-sequence lifetime for a wide range of planet masses and orbital architectures. For hot Jupiters, the stellar spin axis is strongly coupled to the orbital axis, and obliquity excitation requires a strong perturber, usually located within 1-2 AU for a giant planet companion. For warm Jupiters, the spin and orbital axes are more weakly coupled, and the resonance may be achieved for distant giant planet perturbers (at several to tens of AU). Resonant obliquity excitation is accompanied by a decrease in mutual inclination between the inner planet and perturber, and can thus erase high mutual inclinations. Since warm Jupiters have a high occurrence rate of distant planetary companions with appropriate properties for resonant obliquity excitation, stellar obliquities in warm Jupiter systems may be common. This is particularly the case for warm Jupiters orbiting cool stars that have undergone significant spin-down.

[4]  arXiv:1806.07893 [pdf, other]
Title: UniverseMachine: The Correlation between Galaxy Growth and Dark Matter Halo Assembly from z=0-10
Comments: 50 pages; MNRAS submitted. Data and code available at this http URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present a method to flexibly and self-consistently determine individual galaxies' star formation rates (SFRs) from their host haloes' potential well depths, assembly histories, and redshifts. The method is constrained by galaxies' observed stellar mass functions, SFRs (specific and cosmic), quenched fractions, UV luminosity functions, UV-stellar mass relations, autocorrelation functions (including quenched and star-forming subsamples), and quenching dependence on environment; each observable is reproduced over the full redshift range available, up to 0<z<10. Key findings include: galaxy assembly correlates strongly with halo assembly; quenching at z>1 correlates strongly with halo mass; quenched fractions at fixed halo mass decrease with increasing redshift; massive quenched galaxies reside in higher-mass haloes than star-forming galaxies at fixed galaxy mass; star-forming and quenched galaxies' star formation histories at fixed mass differ most at z<0.5; satellites have large scatter in quenching timescales after infall, and have modestly higher quenched fractions than central galaxies; Planck cosmologies result in up to 0.3 dex lower stellar mass-halo mass ratios at early times; and, nonetheless, stellar mass-halo mass ratios rise at z>5. Also presented are revised stellar mass-halo mass relations for all, quenched, star-forming, central, and satellite galaxies; the dependence of star formation histories on halo mass, stellar mass, and galaxy SSFR; quenched fractions and quenching timescale distributions for satellites; and predictions for higher-redshift galaxy correlation functions and weak lensing surface densities. The public data release includes the massively parallel (>10^5 cores) implementation (the UniverseMachine), the newly compiled and remeasured observational data, derived galaxy formation constraints, and mock catalogs including lightcones.

[5]  arXiv:1806.07894 [pdf, other]
Title: Resonant relaxation in globular clusters
Comments: Submitted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Resonant relaxation has been discussed as an efficient process that changes the angular momenta of stars orbiting around a central supermassive black hole due to the fluctuating gravitational field of the stellar cluster. Other spherical stellar systems, such as globular clusters, exhibit a restricted form of this effect where enhanced relaxation rate only occurs in the directions of the angular momentum vectors, but not in their magnitudes; this is called vector resonant relaxation (VRR). To explore this effect, we performed a large set of direct N-body simulations, with up to 512k particles and ~500 dynamical times. Contrasting our simulations with Spitzer-style Monte Carlo simulations, that by design only exhibit 2-body relaxation, we show that the temporal behavior of the angular momentum vectors in $N$-body simulations cannot be explained by 2-body relaxation alone. VRR operates efficiently in globular clusters with $N>10^4$. The fact that VRR operates in globular clusters may open way to use powerful tools in statistical physics for their description. In particular, since the distribution of orbital planes relaxes much more rapidly than the distribution of the magnitude of angular momentum and the radial action, the relaxation process reaches an internal statistical equilibrium in the corresponding part of phase space while the whole cluster is generally out of equilibrium, in a state of quenched disorder. We point out the need to include effects of VRR in Monte Carlo simulations of globular clusters.

[6]  arXiv:1806.07895 [pdf, other]
Title: Cepheids in M31 - The PAndromeda Cepheid sample
Comments: 79 pages, 39 figures, 8 tables, accepted for publication in AJ, K18b is submittted to ApJ, electronic data will be available on CDS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

We present the largest Cepheid sample in M31 based on the complete Pan-STARRS1 survey of Andromeda (PAndromeda) in the $r_{\mathrm{P1}}$ , $i_{\mathrm{P1}}$ and $g_{\mathrm{P1}}$ bands. We find 2686 Cepheids with 1662 fundamental mode Cepheids, 307 first-overtone Cepheids, 278 type II Cepheids and 439 Cepheids with undetermined Cepheid type. Using the method developed by Kodric et al. (2013) we identify Cepheids by using a three dimensional parameter space of Fourier parameters of the Cepheid light curves combined with a color cut and other selection criteria. This is an unbiased approach to identify Cepheids and results in a homogeneous Cepheid sample. The Period-Luminosity relations obtained for our sample have smaller dispersions than in our previous work. We find a broken slope that we previously observed with HST data in Kodric et al. (2015), albeit with a lower significance.

[7]  arXiv:1806.07897 [pdf, other]
Title: Beyond subhalos: Probing the collective effect of the Universe's small-scale structure with gravitational lensing
Comments: 24 pages + appendices, 12 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

Gravitational lensing has emerged as a powerful probe of the matter distribution on subgalactic scales, which itself may contain important clues about the fundamental origins and properties of dark matter. Broadly speaking, two different approaches have been taken in the literature to map the small-scale structure of the Universe using strong lensing, with one focused on measuring the position and mass of a small number of discrete massive subhalos appearing close in projection to lensed images, and the other focused on detecting the collective effect of all the small-scale structure between the lensed source and the observer. In this paper, we follow the latter approach and perform a detailed study of the sensitivity of galaxy-scale gravitational lenses to the ensemble properties of small-scale structure. As in some previous studies, we adopt the language of the substructure power spectrum to characterize the statistical properties of the small-scale density field. We present a comprehensive theory that treats lenses with extended sources as well as those with time-dependent compact sources (such as quasars) in a unified framework for the first time. Our approach uses mode functions to provide both computational advantages and insights about couplings between the lens and source. The goal of this paper is to develop the theory and gain the intuition necessary to understand how the sensitivity to the substructure power spectrum depends on the source and lens properties, with the eventual aim of identifying the most promising targets for such studies.

[8]  arXiv:1806.07899 [pdf, other]
Title: Improving dynamical mass constraints for intermediate-period substellar companions using Gaia DR2
Comments: 5 pages, 4 figures. Accepted for publication in A&A 15/06/2018
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

The relationship between luminosity and mass is of fundamental importance for direct imaging studies of brown dwarf and planetary companions to stars. In principle this can be inferred from theoretical mass-luminosity models; however, these relations have not yet been thoroughly calibrated, since there is a lack of substellar companions for which both the brightness and mass have been directly measured. One notable exception is GJ 758 B, a brown dwarf companion in a $\sim$20 AU orbit around a nearby Sun-like star, which has been both directly imaged and dynamically detected through a radial velocity trend in the primary. This has enabled a mass constraint for GJ 758 B of 42$^{+19}_{-7}$ $M_{\rm Jup}$. Here, we note that Gaia is ideally suited for further constraining the mass of intermediate-separation companions such as GJ 758 B. A study of the differential proper motion, $\Delta \mu$, with regards to HIPPARCOS is particularly useful in this context, as it provides a long time baseline for orbital curvature to occur. By exploiting already determined orbital parameters, we show that the dynamical mass can be further constrained to $42.4^{+5.6}_{-5.0}\, M_{\rm Jup}$ through the Gaia-HIPPARCOS $\Delta \mu$ motion. We compare the new dynamical mass estimate with substellar evolutionary models and confirm previous indications that there is significant tension between the isochronal ages of the star and companion, with a preferred stellar age of $\leq 5$ Gyr while the companion is only consistent with very old ages of $\geq 8$ Gyr.

[9]  arXiv:1806.07901 [pdf, ps, other]
Title: Extreme Population III Starbursts and Direct Collapse Black Holes Stimulated by High Redshift Quasars
Authors: Jarrett L. Johnson (LANL), Aycin Aykutalp (LANL)
Comments: 7 pages, 7 figures, 2 tables; submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

High redshift quasars emit copious X-ray photons which heat the intergalactic medium to temperatures up to $\sim$ 10$^6$ K. At such high temperatures the primordial gas will not form stars until it is assembled into dark matter haloes with masses of $\sim$ 10$^{11}$ M$_{\odot}$, at which point the hot gas collapses and cools under the influence of gravity. Once this occurs, there is a massive reservoir of primordial gas from which stars can form, potentially setting the stage for the brightest Population (Pop) III starbursts in the early Universe. Supporting this scenario, recent observations of quasars at z $\sim$ 6 have revealed a lack of accompanying Lyman $\alpha$ emitting galaxies, consistent with suppression of primordial star formation in haloes with masses below $\sim$ 10$^{10}$ M$_{\odot}$. Here we model the chemical and thermal evolution of the primordial gas as it collapses into such a massive halo irradiated by a nearby quasar in the run-up to a massive Pop III starburst. We show that at distances of $\sim$ 1 Mpc from a typical quasar the conditions are prime for HD cooling to play a role in the evolution of the gas, possibly resulting in a shift to a lower characteristic stellar mass. Within $\sim$ 100 kpc of the highest redshift quasars discovered to date the Lyman-Werner flux produced by the stars in the quasar host galaxy may be high enough to stimulate the formation of a direct collapse black hole (DCBH). Given that metal-enriched outflows are expected to extend out to only $\simeq$ 50 kpc from high-z quasars, this suggests that there is ample unpolluted primordial gas for the formation of DCBHs and Pop III starbursts. How frequently these objects form can be constrained with the James Webb Space Telescope in the coming years.

[10]  arXiv:1806.07902 [pdf, other]
Title: Survey parameters for detecting 21cm - Ly$α$ emitter cross correlations with the Square Kilometre Array
Comments: 5 pages, 3 figures, accepted for publication in MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

Detections of the cross correlation signal between the 21cm signal during reionization and high-redshift Lyman Alpha emitters (LAEs) are subject to observational uncertainties which mainly include systematics associated with radio interferometers and LAE selection. These uncertainties can be reduced by increasing the survey volume and/or the survey luminosity limit, i.e. the faintest detectable Lyman Alpha (Ly$\alpha$) luminosity. We use our model of high-redshift LAEs and the underlying reionization state to compute the uncertainties of the 21cm-LAE cross correlation function at $z\simeq6.6$ for observations with SKA1-Low and LAE surveys with $\Delta z=0.1$ for three different values of the average IGM ionization state ($\langle\chi_\mathrm{HI}\rangle$=0.1, 0.25, 0.5). At $z\simeq6.6$, we find SILVERRUSH type surveys, with a field of view of 21 deg$^2$ and survey luminosity limits of $L_\alpha\geq7.9\times10^{42}$erg~s$^{-1}$, to be optimal to distinguish between an inter-galactic medium (IGM) that is 50%, 25% and 10% neutral, while surveys with smaller fields of view and lower survey luminosity limits, such as the 5 and 10 deg$^2$ surveys with WFIRST, can only discriminate between a 50% and 10% neutral IGM.

[11]  arXiv:1806.07905 [pdf, other]
Title: Magnification Bias of Distant Galaxies in the Hubble Frontier Fields: Testing Wave vs. Particle Dark Matter Predictions
Comments: 46 pages, 23 figures, submitted to ApJ, comments welcome
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Acting as powerful gravitational lenses, the strong lensing galaxy clusters of the deep {\it Hubble} Frontier Fields (HFF) program permit access to lower-luminosity galaxies lying at higher redshifts than hitherto possible. We analyzed the HFF to measure the volume density of Lyman-break galaxies at $z > 4.75$ by identifying a complete and reliable sample up to $z \simeq 10$. A marked deficit of such galaxies was uncovered in the highly magnified regions of the clusters relative to their outskirts, implying that the magnification of the sky area dominates over additional faint galaxies magnified above the flux limit. This negative magnification bias is consistent with a slow rollover at the faint end of the UV luminosity function, and indicates a preference for Bose-Einstein condensate dark matter with a light boson mass of $m_\mathrm{B} \simeq 10^{-22} \, \mathrm{eV}$ over standard cold dark matter. We emphasize that measuring the magnification bias requires no correction for multiply lensed images (with typically three or more images per source), whereas directly reconstructing the luminosity function will lead to an overestimate unless such images can be exhaustively matched up, especially at the faint end that is accessible only in the strongly lensed regions. In addition, we detected a distinctive downward transition in galaxy number density at $z \gtrsim 8$, which may be linked to the relatively late reionization reported by {\it Planck}. Our results suggests that {\it JWST} will likely peer into an "abyss" with essentially no galaxies detected in deep NIR imaging at $z > 10$.

[12]  arXiv:1806.07907 [pdf, other]
Title: The Fastest Travel Together: Chemical Tagging of the Fastest Stars in Gaia DR2 to the Stellar Halo
Comments: 13 pages, 5 figures, 3 tables. In the referee process (minor edits requested by referee)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

The fastest moving stars provide insight into several fundamental properties of the Galaxy, including the escape velocity as a function of Galactocentric radius, the total mass, and the nature and frequency of stellar encounters with the central supermassive black hole. The recent second data release of Gaia has allowed the identification of new samples of stars with extreme velocities. Discrimination among the possible origins of these stars is facilitated by chemical abundance information. We here report the results from our high-resolution spectroscopic followup, using the Apache Point Observatory, of five late-type `hypervelocity' star candidates, characterised by total Galactic rest-frame velocities between 500-600 km/s and estimated to have a probability larger than 50% to be unbound from the Milky Way. Our new results confirm the Gaia DR2 radial velocities to within 1 km/s. We derived stellar atmospheric parameters and chemical abundances for several species including $\alpha$-elements (Mg, Ti, Si, Ca), Fe-peak elements (Fe, Ni, Co, Cr, Mn), neutron-capture elements (Sr, Y, Zr, Ba, La, Nd, Eu) and odd-Z elements (Na, Al, K, V, Cu, Sc). We find that all stars observed are metal-poor giants with -2 $\leq$ [Fe/H] $\leq$ -1 dex and are chemically indistinguishable from typical halo stars. Our results are supported by the chemical properties of four additional stars with extreme space motions which were observed by existing spectroscopic surveys. We conclude that these stars are simply the high-velocity tail of the stellar halo and effectively rule out more exotic origins such as from the Galactic centre or the Large Magellanic Cloud.

[13]  arXiv:1806.07922 [pdf, ps, other]
Title: First constraints on the stellar mass function of star-forming clumps at the peak of cosmic star formation
Authors: Miroslava Dessauges-Zavadsky (Geneva Obs), Angela Adamo (Stockholm University)
Comments: 5 pages, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Star-forming clumps dominate the rest-frame ultraviolet morphology of galaxies at the peak of cosmic star formation. If turbulence driven fragmentation is the mechanism responsible for their formation, we expect their stellar mass function to follow a power-law of slope close to $-2$. We test this hypothesis performing the first analysis of the stellar mass function of clumps hosted in galaxies at $z\sim 1-3.5$. The clump sample is gathered from the literature with similar detection thresholds and stellar masses determined in a homogeneous way. To overcome the small number statistics per galaxy (each galaxy hosts up to a few tens of clumps only), we combine all high-redshift clumps. The resulting clump mass function follows a power-law of slope $\sim -1.7$ and flattens at masses below $2\times 10^7$ M$_{\odot}$. By means of randomly sampled clump populations, drawn out of a power-law mass function of slope $-2$, we test the effect of combining small clump populations, detection limits of the surveys, and blending on the mass function. Our numerical exercise reproduces all the features observed in the real clump mass function confirming that it is consistent with a power-law of slope $\simeq -2$. This result supports the high-redshift clump formation through fragmentation in a similar fashion as in local galaxies, but under different gas conditions.

[14]  arXiv:1806.07932 [pdf, other]
Title: Onboard Automated CME Detection Algorithm for Visible Emission Line Coronagraph on ADITYA-L1
Comments: 28 pages, 10 figures and 5 tables. Accepted for publication in Solar Physics
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

ADITYA-L1 is India's first space mission to study the Sun from Lagrangian 1 position. { \textit{Visible Emission Line Coronagraph}} (VELC) is one of the seven payloads in ADITYA-L1 mission scheduled to be launched around 2020. One of the primary objectives of the VELC is to study the dynamics of coronal mass ejections (CMEs) in the inner corona. This will be accomplished by taking high resolution ($\approx$ 2.51 arcsec pixel$^{-1}$) images of corona from 1.05 R$_{\odot}$ -- 3 R$_{\odot}$ at high cadence of 1 s in 10 \AA\ passband centered at 5000 \AA. Due to limited telemetry at Lagrangian 1 position we plan to implement an onboard automated CME detection algorithm. The detection algorithm is based on the intensity thresholding followed by the area thresholding in successive difference images spatially re-binned to improve signal to noise ratio. We present the results of the application of this algorithm on the data from existing space- and ground-based coronagraph. Since, no existing space-based coronagraph has FOV similar to VELC, we have created synthetic coronal images for VELC FOV after including photon noise and injected different type of CMEs. The performance of CME detection algorithm is tested on these images. We found that for VELC images, the telemetry can be reduced by a factor of 85\% or more keeping CME detection rate of 70\% or above at the same time. Finally, we discuss the advantages and disadvantages of this algorithm. The application of such onboard algorithm in future will enable us to take higher resolution images with improved cadence from space and also reduce the load on limited telemetry at the same time. This will help in better understanding of CMEs by studying their characteristics with improved spatial and temporal resolutions.

[15]  arXiv:1806.07935 [pdf, ps, other]
Title: On $ε$-mechanism driven pulsations in VV 47
Comments: Accepted for publication in MNRAS, 6 pages, 2 tables, 3 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We report new observations of the central star of the planetary nebula VV 47 carried out to verify earlier assertions that the short-period pulsation modes detected in the star are driven by the $\epsilon$ mechanism. In our data, VV 47 was not variable up to a limit of 0.52 mmag in the Fourier amplitude spectrum up to the Nyquist frequency of 21.7 mHz. Given this null result we re-analyzed the data set in which oscillations were claimed. After careful data reduction, photometry, extinction correction, and analysis with a conservative criterion of S/N $\geq$ 4 in the Fourier amplitude spectrum, we found that the star was not variable during the original observations. The oscillations reported earlier were due to an over-optimistic detection criterion. We conclude that VV 47 did not pulsate during any measurements at hand; the observational detection of $\epsilon$-driven pulsations remains arduous.

[16]  arXiv:1806.07938 [pdf, other]
Title: Fast Iterative Tomographic Wave-front Estimation with Recursive Toeplitz Reconstructor Structure for Large Scale Systems
Comments: 16 pages, 17 figures, Paper accepted for publication in "Journal of the Optical Society of America A"
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Tomographic wave-front reconstruction is the main computational bottleneck to realize real-time correction for turbulence-induced wave-front aberrations in future laser-assisted tomographic adaptive-optics (AO) systems for ground-based Giant Segmented Mirror Telescopes (GSMT), because of its unprecedented number of degrees of freedom, $N$, i.e. the number of measurements from wave-front sensors (WFS). In this paper, we provide an efficient implementation of the minimum-mean-square error (MMSE) tomographic wave-front reconstruction mainly useful for some classes of AO systems not requiring a multi-conjugation, such as laser-tomographic AO (LTAO), multi-object AO (MOAO) and ground-layer AO (GLAO) systems, but also applicable to multi-conjugate AO (MCAO) systems. This work expands that by R. Conan [ProcSPIE, 9148, 91480R (2014)] to the multi-wave-front, tomographic case using natural and laser guide stars. The new implementation exploits the Toeplitz structure of covariance matrices used in a MMSE reconstructor, which leads to an overall $O(N\log N)$ real-time complexity compared to $O(N^2)$ of the original implementation using straight vector-matrix multiplication. We show that the Toeplitz-based algorithm leads to 60\,nm rms wave-front error improvement for the European Extremely Large Telescope Laser-Tomography AO system over a well-known sparse-based tomographic reconstruction, but the number of iterations required for suitable performance is still beyond what a real-time system can accommodate to keep up with the time-varying turbulence

[17]  arXiv:1806.07967 [pdf, other]
Title: Water and interstellar complex organics associated with the HH 212 protostellar disc - On disc atmospheres, disc winds, and accretion shocks
Comments: Astronomy & Astrophysics, in press
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

The HH 212 protostellar system, in Orion B, has been mapped thanks to ALMA-Band 7 Cycle 1 and Cycle 4 observations of dueterated water (HDO) and acetaldehyde (CH$_3$CHO) emission with an angular resolution down to $\sim$0.15 arcsec (60 au). Many emission lines due to 14 CH$_3$CHO and 1 HDO transitions at high excitation ($E_{\rm u}$ between 163 K and 335 K) have been imaged in the inner $\sim$ 70 au region. The local thermal equilibrium analysis of the CH$_3$CHO emission leads to a temperature of 78$\pm$14 K and a column density of 7.6$\pm$3.2 $\times$ 10$^{15}$ cm$^{-2}$, which, when $N_{\rm H_2}$ of 10$^{24}$ cm$^{-2}$ is assumed, leads to an abundance of $X_{\rm CH_3CHO}$ $\simeq$ 8 $\times$ 10$^{-9}$. The large velocity gradient analysis of the HDO emission also places severe constraints on the volume density, n$_{\rm H_2}$ $\geq$ 10$^8$ cm$^{-3}$. The line profiles are 5--7 km s$^{-1}$ wide, and CH$_3$CHO and HDO both show a $\pm$ 2 km s$^{-1}$ velocity gradient over a size of $\sim$ 70 au (blue-shifted emission towards the north-west and red-shifted emission towards the south-east) along the disc equatorial plane, in agreement with what was found so far using other molecular tracers. The kinematics of CH$_3$CHO and HDO are consistent with the occurrence of a centrifugal barrier, that is, the infalling envelope-rotating disc ring, which is chemically enriched through low-velocity accretion shocks. The emission radius is $\sim$ 60 au, in good agreement with what was found before for another interstellar complex organic molecule such as NH$_2$CHO. We support a vertical structure for the centrifugal barrier, suggesting the occurrence of two outflowing, expanding, and rotating rings above and below (of about 40-45 au) the optically thick equatorial disc plane. It is tempting to speculate that these rings could probe the basis of a wind launched from this region.

[18]  arXiv:1806.07973 [pdf, other]
Title: Dense Molecular Gas in the Nearby Low Metallicity Dwarf Starburst Galaxy IC 10
Comments: Accepted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Dense molecular gas and star formation are correlated in galaxies. The effect of low metallicity on this relationship is crucial for interpreting observations of high redshift galaxies, which have lower metallicities than galaxies today. However, it remains relatively unexplored because dense molecular gas tracers like HCN and HCO+ are faint in low metallicity systems. We present Green Bank Telescope observations of HCN(1-0) and HCO+(1-0) on giant molecular cloud (34pc) scales in the nearby low metallicity ($12+\log({\rm O/H})=8.2$) starburst IC 10 and compare them to those in other galaxies. We detect HCN and HCO+ in one and three of five pointings, respectively. The $I_{\rm HCN}/I_{\rm HCO+}$ values are within the range seen in other galaxies, but are most similar to those seen in other low metallicity sources and in starbursts. The detections follow the fiducial $L_{\rm IR}$-$L_{\rm HCN}$ and $L_{\rm IR}$-$L_{\rm HCO+}$ relationships. These trends suggest that HCN and HCO+ can be used to trace dense molecular gas at metallicities of 1/4 $Z_\odot$, to first order. The dense gas fraction is similar to that in spiral galaxies, but lower than that in U/LIRGs. The dense molecular gas star formation efficiency, however, is on the upper end of those in normal galaxies and consistent with those in U/LIRGs. These results suggest that the CO and HCN/HCO+ emission occupy the same relative volumes as at higher metallicity, but that the entire emitting structure is reduced in size. Dense gas mass estimates for high redshift galaxies may need to be corrected for this effect.

[19]  arXiv:1806.07979 [pdf, other]
Title: Measuring the Local ISM along the Sight Lines of the Two Voyager Spacecraft with HST/STIS
Authors: Julia Zachary (1), Seth Redfield (1), Jeffrey L. Linsky (2), Brian E. Wood (3) ((1) Wesleyan University, (2) University of Colorado and NIST, (3) Naval Research Laboratory)
Comments: 22 pages, 5 figures, published in ApJ
Journal-ref: Zachary, J., Redfield, S., Linsky, J. L., & Wood, B. E. 2018, ApJ, 859, 42
Subjects: Astrophysics of Galaxies (astro-ph.GA); Earth and Planetary Astrophysics (astro-ph.EP)

In 2012, Voyager 1 crossed the heliopause, becoming the first human-made object to exit the solar system. This milestone signifies the beginning of an important new era for local interstellar medium (LISM) exploration. We present measurements of the structure and composition of the LISM in the immediate path of the Voyager spacecraft by using high-resolution Hubble Space Telescope (HST) spectra of nearby stars that lie along the same lines of sight. We provide a comprehensive inventory of LISM absorption in the near-ultraviolet (2600-2800 Angstroms) and far-ultraviolet (1200-1500 Angstroms). The LISM absorption profiles are used to make comparisons between each pair of closely spaced (<15 deg) sight lines. With fits to several absorption lines, we make measurements of the physical properties of the LISM. We estimate electron density along the Voyager 2 sight line, and our values are consistent with recent measurements by Voyager 1. Excess absorption in the HI Ly-alpha line displays the presence of both the heliosphere and an astrosphere around GJ 780. This is only the 14th detection of an astrosphere, and the large mass-loss rate ($\dot{M} = 10\dot{M}_\odot$) is consistent with other subgiant stars. The heliospheric absorption matches the predicted strength for a sight line 58 deg from the upwind direction. As both HST and Voyager reach the end of their lifetimes, we have the opportunity to synthesize their respective observations, combining in situ measurements with the shortest possible line-of-sight measurements to study the Galactic ISM surrounding the Sun.

[20]  arXiv:1806.07991 [pdf, other]
Title: Constraints on Axion-like Particles and Nucleon Pairing in Dense Matter from the Hot Neutron Star in HESS J1731-347
Comments: 15 pages, 10 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

If the thermal evolution of the hot young neutron star in the supernova remnant HESS J1731-347 is driven by neutrino emission, it provides a stringent constraint on the coupling of light (mass $\ll 10$ keV) axion-like particles to neutrons. Using Markov-Chain Monte Carlo we find that for the values of axion-neutron coupling $g_{ann}^2 > 7.7 \times 10^{-20}$ (90% c.l.) the axion cooling from the bremsstrahlung reaction $n+n\rightarrow n+n +a$ is too rapid to account for the high observed surface temperature. This implies that the Pecci-Quinn scale or axion decay constant $f_a > 6.7 \times 10^7$ GeV for KSVZ axions and $f_a > 1.7 \times 10^9$ GeV for DFSZ axions. The high temperature of this neutron star also allows us to tighten constraints on the size of the nucleon pairing gaps.

[21]  arXiv:1806.08014 [pdf, other]
Title: The Solar Twin Planet Search: The age - chromospheric activity relation
Comments: 14 pages, 8 figures, 3 Tables. Accepted for publication in A&A. [Abridged abstract]
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

It is well known that the magnetic activity of solar type stars decreases with age, but it is widely debated in the literature whether there is a smooth decline or if there is an early sharp drop until 1-2 Gyr followed by a relatively inactive constant phase. We revisited the activity-age relation using time-series observations of a large sample of solar twins whose precise isochronal ages and other important physical parameters have been determined. We measured the Ca II H and K activity indices using 9000 HARPS spectra of 82 solar twins. We measured an average solar activity of $S_{\rm MW}$ = 0.1712 $\pm$ 0.0017 during solar magnetic cycles 23$-$24 covered by HARPS observations and we also inferred an average of $S_{\rm MW}$ = 0.1694 $\pm$ 0.0025 for cycles 10$-$24, anchored on a S index vs. sunspot number correlation. Also, a simple relation between the average and dispersion of the activity levels of solar twins was found. This enabled us to predict the stellar variability effects on the age-activity diagram and, consequently, estimate the chromospheric age uncertainties due to the same phenomena. The age-activity relation is still statistically significant up to ages around 6$-$7 Gyr, in agreement with previous works using open clusters and field stars with precise ages. Our research confirms that Ca II H \& K lines remain a useful chromospheric evolution tracer until stars reach ages of at least 6$-$7 Gyr. We found an evidence that, for the most homogeneous set of old stars, the chromospheric activity indices seem to continue decreasing after the solar age towards the end of the main-sequence. Our results indicate that a significant part of the scatter observed in the age-activity relation of solar twins can be attributed to stellar cycle modulations effects. The Sun seems to have a normal activity level and variability for its age.

[22]  arXiv:1806.08017 [pdf, other]
Title: An Unexpectedly Small Emission Region Size Inferred from Strong High-Frequency Diffractive Scintillation in GRB 161219B
Comments: 14 pages, 7 figures, 1 table. Submitted to ApJ; comments welcome
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present Karl G. Jansky Very Large Array radio observations of the long GRB 161219B ($z=0.147$) spanning $1-37$ GHz. The data exhibit unusual behavior, including sharp spectral peaks and minutes-timescale large amplitude variability centered at $20$ GHz and spanning the full frequency range. We attribute this behavior to scattering of the radio emission by the turbulent ionized Galactic interstellar medium (ISM), including both diffractive and refractive scintillation. However, the scintillation is much stronger than predicted by a model of the Galactic electron density distribution (NE2001); from the measured variability timescale and decorrelation bandwidth we infer a scattering measure of $SM\approx 3.8\times 10^{-3}$ kpc m$^{-20/3}$ ($15$ times larger than predicted in NE2001) and a scattering screen distance of $d_{\rm scr}\approx 0.6$ kpc. We infer an emission region size of $\theta_s \approx 2$ $\mu$as ($\approx 2\times 10^{16}$ cm) at $\approx4$ days, and find that prior to 8 days the source size is an order of magnitude smaller than model predictions for a uniformly illuminated disk or limb-brightened ring, indicating a slightly off-axis viewing angle or significant substructure in the emission region. Simultaneous multi-hour broadband radio observations of future GRB afterglows will allow us to characterize the scintillation more completely, and hence to probe the observer viewing angle, the evolution of the jet Lorentz factor, the structure of the afterglow emission regions, and ISM turbulence at high Galactic latitudes.

[23]  arXiv:1806.08024 [pdf, ps, other]
Title: Swift Observations of the bright uncatalogued X-ray transient MAXI J1535-571
Comments: 13 pages, 9 figures, 2 tables. Submitted to MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The black hole candidate MAXI J1535-571 is a recently discovered X-ray transient. We report on the monitoring observations of Swift Gamma-Ray Burst Mission during outburst. The source transits from the hard state to the intermediate state, and reaches the soft state; near the end of the outburst, it returns to the hard state passing through the low intermediate state, following a typical Q-shaped loop in the hardness-intensity diagram. During the high intermediate state, detailed spectral analyses using a multi-temperature disk model reveal that the disk luminosity is flatter than the inner disk temperature to the fourth power, and the disk temperature profile varies as the disk radius raised to the power of -0.5, consistent with the behavior of a slim disk, implying that the disk structure has been modified due to the high luminosity of ~ 10^{39} erg/s. Meanwhile, the column density increases with the Eddington ratio, suggesting that the outflow matters are driven by radiation pressure due to the high accretion rate.

[24]  arXiv:1806.08033 [pdf, other]
Title: On the Rate of Abiogenesis from a Bayesian Informatics Perspective
Comments: accepted by Astrobiology
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Life appears to have emerged relatively quickly on the Earth, a fact sometimes used to justify a high rate of spontaneous abiogenesis ($\lambda$) among Earth-like worlds. Conditioned upon a single datum - the time of earliest evidence for life ($t_{\mathrm{obs}}$) - previous Bayesian formalisms for the posterior distribution of $\lambda$ have demonstrated how inferences are highly sensitive to the priors. Rather than attempt to infer the true $\lambda$ posterior, we here compute the relative change to $\lambda$ when new experimental/observational evidence is introduced. By simulating posterior distributions and resulting entropic information gains, we compare three experimental pressures on $\lambda$: 1) evidence for an earlier start to life; $t_{\mathrm{obs}}$; 2) constraints on spontaneous abiogenesis from the lab; and 3) an exoplanet survey for biosignatures. First, we find that experiments 1 and 2 can only yield lower limits on $\lambda$, unlike 3. Second, evidence for an earlier start to life can yield negligible information on $\lambda$ if $t_{\mathrm{obs}} \ll \lambda_{\mathrm{max}}^{-1}$. Vice versa, experiment 2 is uninformative when $\lambda_{\mathrm{max}} \gg t_{\mathrm{obs}}^{-1}$. Whilst experiment 3 appears the most direct means of measuring $\lambda$, we highlight that early starts inform us of the conditions of abiogenesis, and that lab experiments could succeed in building new life. Together then, the three experiments are complimentary and we encourage activity in all to solve this grand challenge.

[25]  arXiv:1806.08034 [pdf]
Title: Design of Near Infrared Sky Brightness Monitor and Test Running at Ngari Observatory in Tibet
Comments: 19 pages,18 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Tibet is known as the third pole of the earth, as high as the South Pole and North Pole. The Ngari (Ali) observatory in Tibet has the advantage of plenty of photometric night, low precipitable water vapor, high transmittance, good seeing. It is a good site, and promising to be one of the best place for infrared and submillimeter observations in the world. However, there is no data available for sky background brightness in such place, which restrict the astronomical development of the sites. In the near infrared band of J, H, Ks, a NIR sky brightness monitor (NISBM) is designed based on InGaAs photoelectric diode. By using the method of chopper modulation and digital lock-in amplifier processing, the SNR (Signal Noise Ratio), detectivity and the data acquisition speed of the device is greatly improved. For each band of J, H, Ks, an independent instrument is designed and calibrated in laboratory. The NISBM has been installed in Ngari observatory in July of 2017 and obtained the first data of NIR sky brightness at Ngari observatory.

[26]  arXiv:1806.08050 [pdf]
Title: Portable Adaptive Optics for exoplanet imaging
Comments: 21 pages, 11 figures, 3 tables, prepare to submit
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)

The portable adaptive optics (PAO) is a high-contrast instrument that is optimized for the direct imaging of exoplanets and sub-stellar companions. The PAO has a compact physical size, high flexibility and high performance. As a visiting instrument, PAO has been used for the imaging observation of exoplanets with current 3-4 meter class telescopes. In these observations, it has delivered a diffraction limited image in H band. Combined with our unique image rotation and subtraction (IRS) technique and the optimized IRS algorithm, our PAO has successfully recovered the known exoplanets of kappa And b, in recent observation at 3.5-meter ARC telescope at Apache Point Observatory. The observation contrast has reached 10E-5 at an angular distance of 1 arcsec. We have performed the associated astrometry and photometry analysis of the recovered kappa And b planet, which gives a project separation of 1.044 +/- 0.016 arcsec, a position angle of 53.5 +/- 0.5 degrees, and a mass of 10.15 (-1.255) (+2.19) MJup. It has fully demonstrated that our portable high-contrast imaging system can be used for the exoplanets direct imaging observation with middle-class telescopes.

[27]  arXiv:1806.08052 [pdf, ps, other]
Title: Exact solutions of primordial gravitational waves
Comments: 11 pages, 3 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)

The future detection projects of gravitational waves are expected to have the sensitivity of detecting the primordial gravitational waves, which may be useful to get new insight into the very early universe. It is essential to analyze the evolution equation of the gravitational waves to estimate the present field strength of the primordial gravitational waves. In this paper, we obtain analytic solutions of the gravitational wave equation in the presence of non-relativistic matters as well as the cosmological constant. Although it is difficult to obtain the solution directly, we find that the equation for the square of the amplitudes has a simple polynomial solution. This quantity, which is directly related to the energy density of the gravitational waves, turns out to be useful to construct analytic solutions for the amplitudes by using Weierstrass's elliptic functions.

[28]  arXiv:1806.08056 [pdf, other]
Title: Where does Titan Sand Come From: Insight from Mechanical Properties of Titan Sand Candidates
Comments: 17 pages, 5 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Extensive equatorial linear dunes exist on Titan, but the origin of the sand, which appears to be organic, is unknown. We used nanoindentation to study the mechanical properties of a few Titan sand candidates, several natural sands on Earth, and common materials used in the Titan Wind Tunnel, to understand the mobility of Titan sand. We measured the elastic modulus (E), hardness (H), and fracture toughness (Kc) of these materials. Tholin's elastic modulus (10.4+/-0.5 GPa) and hardness (0.53+/-0.03 GPa) are both an order of magnitude smaller than silicate sand, and is also smaller than the mechanically weak white gypsum sand. With a magnitude smaller fracture toughness (Kc=0.036+/-0.007 MPa-m^(1/2)), tholin is also much more brittle than silicate sand. This indicates that Titan sand should be derived close to the equatorial regions where the current dunes are located, because tholin is too soft and brittle to be transported for long distances.

[29]  arXiv:1806.08058 [pdf, ps, other]
Title: Diffuse x-ray emission from the northern arc of loop I observed with suzaku
Comments: 7 pages, 5 figures; accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

After discovery of the Fermi bubbles, giant structures observed in radio to X-rays have been discussed as possi- ble evidence of past activities in the Galactic Center (GC). We report here on the analysis of Suzaku data pointing around the Loop I arc. The diffuse X-ray emission was well represented by the three-component model: (1) an unabsorbed thermal plasma with kT ~ 0.1 keV either from the Local Hot Bubble (LHB) and/or solar wind charge exchange (SWCX), (2) an absorbed thermal plasma regarded as a contribution from the Loop I and the Galactic halo (GH), and (3) an absorbed power-law component representing the cosmic X-ray background. The temper- ature of the absorbed thermal plasma was clustered in a range of 0.30 +- 0.02 keV along Loop I ("ON" regions), whereas the temperature was about 20 % lower in the cavity adjacent to the bubbles and Loop I ("OFF" regions) with 0.24 +- 0.03 keV. The emission measure (EM) varied along the Galactic latitude, and was well correlated with the count rate variation as measured with the ROSAT in 0.75 keV band. Although the amount of neutral gas was not conclusive to constrain on the distance to Loop I, the observed EM values rule out a hypothesis that the structure is close to the Sun; we argue that the Loop I is a distant, kpc structure of the shock-heated GH gas. We discuss the origin of apparent mismatch in the morphologies of the Fermi bubbles and the Loop I arc, suggesting a two-step explosion process in the GC.

[30]  arXiv:1806.08061 [pdf, other]
Title: Interplanetary Scintillation studies with the Murchison Wide-field Array III: Comparison of source counts and densities for radio sources and their sub-arcsecond components at 162 MHz
Comments: Accepted for publication in MNRAS. 11 pages, 7 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We use Murchison Widefield Array observations of interplanetary scintillation (IPS) to determine the source counts of point ($<$0.3 arcsecond extent) sources and of all sources with some subarcsecond structure, at 162 MHz. We have developed the methodology to derive these counts directly from the IPS observables, while taking into account changes in sensitivity across the survey area. The counts of sources with compact structure follow the behaviour of the dominant source population above $\sim$3 Jy but below this they show Euclidean behaviour. We compare our counts to those predicted by simulations and find a good agreement for our counts of sources with compact structure, but significant disagreement for point source counts. Using low radio frequency SEDs from the GLEAM survey, we classify point sources as Compact Steep-Spectrum (CSS), flat spectrum, or peaked. If we consider the CSS sources to be the more evolved counterparts of the peaked sources, the two categories combined comprise approximately 80% of the point source population. We calculate densities of potential calibrators brighter than 0.4 Jy at low frequencies and find 0.2 sources per square degrees for point sources, rising to 0.7 sources per square degree if sources with more complex arcsecond structure are included. We extrapolate to estimate 4.6 sources per square degrees at 0.04 Jy. We find that a peaked spectrum is an excellent predictor for compactness at low frequencies, increasing the number of good calibrators by a factor of three compared to the usual flat spectrum criterion.

[31]  arXiv:1806.08072 [pdf, other]
Title: Explosions of blue supergiants from binary mergers for SN 1987A
Authors: Athira Menon (1), Victor Utrobin (2 and 3), Alexander Heger (1 and 4) ((1) School of Physics and Astronomy, Monash University, Melbourne, Australia, (2) Max-Planck-Institute for Astrophysics, Garching, Germany, (3) Institute for Theoretical and Experimental Physics of National Research Center, Moscow, Russia, (4) Tsung-Dao Lee Institute, Shanghai, China)
Comments: 16 pages, 11 figures, 3 tables, submitted to MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

Based on the work of Menon and Heger (2017), we present the bolometric light curves and spectra of the explosions of blue supergiant progenitors from binary mergers. We study SN 1987A and two other peculiar Type IIP supernovae: SN 1998A and SN 2006V. The progenitor models were produced using the stellar evolution code Kepler and then exploded using the 1D radiation hydrodynamic code Crab. The explosions of binary merger models exhibit an overall better fit to the light curve of SN 1987A than previous single star models, due to their lower helium-core masses, larger envelope masses, and smaller radii. The merger model that best matches the observational constraints of the progenitor of SN 1987A and the light curve, is a model with a radius of 37 solar radii, an ejecta mass of 20.6 solar masses, an explosion energy of 1.7 Bethe, a nickel mass of 0.073 solar masses, and a nickel mixing velocity of 3,000 km/s. This Model also works for SN 1998A and is comparable with earlier estimates from semi-analytic models. In the case of SN 2006V, however, a model with a radius of 150 solar radii and ejecta mass of 19.1 solar masses matches the light curve. These parameters are significantly higher than predictions from semi-analytic models for the progenitor of this supernova.

[32]  arXiv:1806.08093 [pdf, other]
Title: Tidal Disruption of a Main-Sequence Star by an Intermediate-Mass Black Hole: A Bright Decade
Comments: 12 pages, 8 figures, submitted to ApJ on 15th of June, 2018, this is the original submitted version
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

There has been suggestive evidence of intermediate-mass black holes (IMBHs; $10^{3-4} M_\odot$) existing in some globular clusters (GCs) and dwarf galaxies, but IMBHs as a population still remain elusive. As a main-sequence (MS) star passes by an IMBH too close it might be tidally captured and disrupted. We study the long-term accretion and the observational consequence of such tidal disruption events. The disruption radius is hundreds to thousands of the BH's Schwarzschild radius, so the circularization of the falling-back debris stream is very inefficient due to weak general relativity effects. Due to this and a high mass fallback rate, the bound debris initially goes through a $\sim 10$ year long super-Eddington accretion phase. The photospheric emission of the outflow ejected during this phase dominates the observable radiation and peaks in the UV/Optical bands with a luminosity of $\sim 10^{42}\ {\rm erg\ s^{-1}}$. After the accretion rate drops below the Eddington rate, the bolometric luminosity would follow the conventional $t^{-5/3}$ power-law decay, and X-rays from the inner accretion disk starts to be seen. Looking for these luminous and long-term events in GCs and nearby dwarf galaxies could unveil the IMBH population.

[33]  arXiv:1806.08096 [pdf, other]
Title: Gaia-ESO Survey: INTRIGOSS - A new library of High Resolution Synthetic Spectra
Comments: 32 pages, 12 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present a high resolution synthetic spectral library, INTRIGOSS, designed for studying FGK stars. The library is based on atmosphere models computed with specified individual element abundances via ATLAS12 code. Normalized SPectra (NSP) and surface Flux SPectra (FSP), in the 4830-5400 A, wavelength range, were computed with the SPECTRUM code. INTRIGOSS uses the solar composition by Grevesse et al. 2007 and four [alpha/Fe] abundance ratios and consists of 15,232 spectra. The synthetic spectra are computed with astrophysical gf-values derived by comparing synthetic predictions with a very high SNR solar spectrum and the UVES-U580 spectra of five cool giants. The validity of the NSPs is assessed by using the UVES-U580 spectra of 2212 stars observed in the framework of the Gaia-ESO Survey and characterized by homogeneous and accurate atmospheric parameter values and by detailed chemical compositions. The greater accuracy of NSPs with respect to spectra from the AMBRE, GES_Grid, PHOENIX, C14, and B17 synthetic spectral libraries is demonstrated by evaluating the consistency of the predictions of the different libraries for the UVES-U580 sample stars. The validity of the FSPs is checked by comparing their prediction with both observed spectral energy distribution and spectral indices. The comparison of FSPs with SEDs derived from ELODIE, INDO--U.S., and MILES libraries indicates that the former reproduce the observed flux distributions within a few percent and without any systematic trend. The good agreement between observational and synthetic Lick/SDSS indices shows that the predicted blanketing of FSPs well reproduces the observed one, thus confirming the reliability of INTRIGOSS FSPs.

[34]  arXiv:1806.08106 [pdf, other]
Title: SAGE: using CubeSats for Gravitational Wave Detection
Comments: published in SPIE conference proceedings, 2018
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Experiment (hep-ex)

SAGE (SagnAc interferometer for Gravitational wavE) is a fast track project for a space observatory based on multiple 12-U CubeSats in geostationary orbit. The objective of this project is to create a Sagnac interferometer with 73000 km circular arms. The geometry of the interferometer makes it especially sensitive to circularly polarized gravitational waves at frequency close to 1 Hz. The nature of the Sagnac measurement makes it almost insensitive to position error, allowing spacecrafts in ballistic trajectory. The light source and recombination units of the interferometer are based on compact fibered technologies, without the need of an optical bench. The main limitation would come from non-gravitational acceleration of the spacecraft. However, conditionally upon our ability to post-process the effect of solar wind, solar pressure and thermal expansion, we would detect gravitational waves with strains down to 10^-21 over a few days of observation.

[35]  arXiv:1806.08119 [pdf, other]
Title: Rotation period of the minor planet 2010 WC9
Comments: 2 pages with 3 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Photometric observations of the minor planet 2010 WC9 carried out by one of us (Diepvens) in May 14$^{th}$, 2018 have allowed obtain a lightcurve of around 110 minutes and determine the rotation period of this asteroid.

[36]  arXiv:1806.08120 [pdf, other]
Title: Galaxy-galaxy lensing in the outskirts of CLASH clusters: constraints on local shear and testing mass-luminosity scaling relation
Comments: 20 pages, 13 figures, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present a selection of 24 candidate galaxy-galaxy lensing (GGLs) identified from Hubble images in the outskirts of the massive galaxy clusters from the CLASH survey. These GGLs provide insights into the mass distributions at larger scales than the strong lensing region in the cluster cores. We built parametric mass models for three of these GGLs showing simple lensing configurations, in order to assess the properties of their lens and its environment. We show that the local shear estimated from the GGLs traces the gravitational potential of the clusters at 1-2 arcmin radial distance, allowing us to derive their velocity dispersion. We also find a good agreement between the strength of the shear measured at the GGL positions through strong-lensing modelling and the value derived independently from a weak-lensing analysis of the background sources. Overall, we show the advantages of using single GGL events in the outskirts of clusters to robustly constrain the local shear, even when only photometric redshift estimates are known for the source. We argue that the mass-luminosity scaling relation of cluster members can be tested by modelling the GGLs found around them, and show that the mass parameters can vary up to $\sim$30% between the cluster and GGL models assuming this scaling relation.

[37]  arXiv:1806.08134 [pdf, other]
Title: Spectropolarimetric NLTE inversion code SNAPI
Comments: To appear in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Inversion codes are computer programs that fit a model atmosphere to the observed Stokes spectra, thus retrieving the relevant atmospheric parameters. The rising interest in the solar chromosphere, where spectral lines are formed by scattering, requires developing, testing, and comparing new non-local thermal equilibrium (NLTE) inversion codes.
We present a new NLTE inversion code that is based on the analytical computation of the response functions. We named the code SNAPI, which is short for spectropolarimetic NLTE analytically powered inversion. SNAPI inverts full Stokes spectrum in order to obtain a depth-dependent stratification of the temperature, velocity, and the magnetic field vector. It is based on the so-called node approach, where atmospheric parameters are free to vary in several fixed points in the atmosphere, and are assumed to behave as splines in between. We describe the inversion approach in general and the specific choices we have made in the implementation. We test the performance on one academic problem and on two interesting NLTE examples, the Ca\,II\,8542 and Na\,I\,D spectral lines. The code is found to have excellent convergence properties and outperforms a finite-difference based code in this specific implementation by at least a factor of three. We invert synthetic observations of Na lines from a small part of a simulated solar atmosphere and conclude that the Na lines reliably retrieve the magnetic field and velocity in the range $-3<\log \tau < -0.5$.

[38]  arXiv:1806.08137 [pdf, ps, other]
Title: Complex Organic Molecules in Hot Molecular Cores/Corinos: Physics and Chemistry
Authors: Maria T. Beltrán, Víctor M. Rivilla (INAF-Osservatorio Astrofisico di Arcetri)
Comments: 8 pages, 4 figures. An ngVLA Science Book chapter
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

Hot molecular cores (HMCs), the cradles of massive stars, are the most chemically rich sources in the Galaxy. The typical masses of these cores (few hundreds of solar masses) make them the most important reservoirs of complex organic molecules (COMs), including key species for prebiotic processes. This rich chemistry is thought to be the result of the evaporation of dust grain mantles by the strong radiation of the deeply embedded early-type star(s). Our own Sun may have been born in a high-mass star-forming region, so our Earth may have inherited the primordial chemical composition of its parental hot core region, as suggested by recent studies of oxygen and sulfur chemistry in comets. In this chapter, we discuss how the next generation Very Large Array (ngVLA) can help us to study the emission of heavy COMs in both low- and high-mass star-forming regions. The emission of COMs is important not only because it allows us to understand how chemistry may have developed to eventually form life in our Earth, but also because COMs are a powerful tool for studying the physical properties and kinematics of the dense regions very close to the central protostars.

[39]  arXiv:1806.08143 [pdf, ps, other]
Title: Detecting Infall in High-Mass Protostellar Objects
Authors: Maria T. Beltrán (1), Qizhou Zhang (2), Víctor M. Rivilla (1) ((1) INAF-Osservatorio Astrofisico di Arcetri, (2) Harvard-Smithsonian Center for Astrophysics)
Comments: 6 pages, 1 figure. An ngVLA Science Book chapter
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

The role of accretion disks in the formation of low-mass stars has been well assessed by means of high angular resolution observations at various wavelengths. These findings confirm the prediction that conservation of angular momentum during the collapse leading to the formation of a star is bound to produce flattening and rotation of the collapsing core. What about high-mass stars? At present, several authors have reported on detections of disks around high-mass YSOs. Notwithstanding these important results, the presence of disks rotating about high-mass stars is not sufficient by itself to prove unambiguously the accretion model: what is needed is iron-clad evidence of infall. Such evidence is very difficult to find, as the free-fall velocity becomes significant only very close to the accreting star, i.e., over a region of a few 0.01 pc ($\sim$2000 au), which is very difficult to access and disentangle from the surrounding quiescent or rotating material. In this chapter we discuss how to characterize the infall of material in a sample of 36 high-mass accretion disk candidates covering a broad range of luminosities, from 10$^3$ $L_\odot$ to 10$^6$ $L_\odot$, compiled by Beltr\'an & de Wit (2016) with the next generation Very Large Array (ngVLA).

[40]  arXiv:1806.08147 [pdf, other]
Title: Inhibition of the electron cyclotron maser instability in the dense magnetosphere of a hot Jupiter
Comments: 18 pages, 15 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Hot Jupiter (HJ) type exoplanets are expected to produce strong radio emission in the MHz range via the Electron Cyclotron Maser Instability (ECMI). To date, no repeatable detections have been made. To explain the absence of observational results, we conduct 3D adaptive mess refinement (AMR) magnetohydrodynamic (MHD) simulations of the magnetic interactions between a solar type star and HJ using the publicly available code PLUTO. The results are used to calculate the efficiency of the ECMI at producing detectable radio emission from the planets magnetosphere. We also calculate the frequency of the ECMI emission, providing an upper and lower bounds, placing it at the limits of detectability due to Earth's ionospheric cutoff of $\sim 10 \ \mathrm{MHz}$. The incident kinetic and magnetic power available to the ECMI is also determined and a flux of $0.069 \ \mathrm{mJy}$ for an observer at $10 \ \mathrm{pc}$ is calculated. The magnetosphere is also characterized and an analysis of the bow shock which forms upstream of the planet is conducted. This shock corresponds to the thin shell model for a colliding wind system. A result consistent with a colliding wind system. The simulation results show that the ECMI process is completely inhibited by the planets expanding atmosphere, due to absorption of UV radiation form the host star. The density, velocity, temperature and magnetic field of the planetary wind are found to result in a magnetosphere where the plasma frequency is raised above that due to the ECMI process making the planet undetectable at radio MHz frequencies.

[41]  arXiv:1806.08148 [pdf, other]
Title: Intra-day optical multi-band quasi-simultaneous observation of BL Lacertae object S5 0716+714 from 2013 to 2016
Comments: Published in MNRAS
Journal-ref: MNRAS 478 (2018) 3513
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

We perform quasi-simultaneous optical multi-band monitoring of BL Lac object S5 0716+714 on seven nights from 2013 to 2016. Intra-day variability (IDV) is found on all seven nights. The source was faintest on JD 2456322 with 14.15 mags and brightest on JD 2457437 with 12.51 mags in the $R$ band. The maximum intra-day variation we observed is 0.15 mags in the $B$ band on JD 2456322. Both bluer-when-brighter and achromatic spectral behaviours were observed on the intra-day timescale. On the longer-term scale, the object exhibited a mild bluer-when-brighter behaviour between the $B$ and $R$ bands. We estimate the inter-band lags using two independent methods. The variation in the $B$ band was observed to lag that in the $I$ band by about 15 minutes on JD 2457315. We compare this lag with one reported previously and discussed the origin of these lags.

[42]  arXiv:1806.08155 [pdf, other]
Title: 3D radiative transfer: Continuum and line scattering in non-spherical winds from OB stars
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Context: State of the art quantitative spectroscopy of OB-stars compares synthetic spectra (calculated by means of 1D, spherically symmetric computer codes) with observations. Certain stellar atmospheres, however, show strong deviations from spherical symmetry, and need to be treated in 3D. Aims: We present a newly developed 3D radiative transfer code, tailored to the solution of the radiation field in rapidly expanding stellar atmospheres. We apply our code to the continuum transfer in wind-ablation models, and to the UV resonance line formation in magnetic winds. Methods: We have used a 3D finite-volume method for the solution of the equation of radiative transfer, to study continuum- and line-scattering problems. Convergence has been accelerated by a non-local approximate Lambda-iteration scheme. Particular emphasis has been put on careful (spherically symmetric) test cases. Results: Typical errors of the source functions, when compared to 1D solutions, are of the order of 10-20 %, and increase for optically thick continua. In circumstellar discs, the radiation temperatures in the (optically thin) transition region from wind to disc are quite similar to corresponding values in the wind. For MHD simulations of dynamical magnetospheres, the line profiles, calculated with our 3D code, agree well with previous solutions using a 3D-SEI method. When compared with profiles resulting from the `analytic dynamical magnetosphere' (ADM) model, significant differences become apparent. Conclusions: Due to similar radiation temperatures in the wind and the transition region to the disc, the same line-strength distribution can be applied within radiation hydrodynamic calculations for circumstellar discs in `accreting high-mass stars'. To properly describe the UV line formation in dynamical magnetospheres, the ADM model needs to be further developed, at least in a large part of the outer wind.

[43]  arXiv:1806.08158 [pdf, ps, other]
Title: Energy Deposition by Energetic Electrons in a Diffusive Collisional Transport Model
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

A considerable fraction of the energy in a solar flare is released as suprathermal electrons; such electrons play a major role in energy deposition in the ambient atmosphere and hence the atmospheric response to flare heating. Historically the transport of these particles has been approximated through a deterministic approach in which first-order secular energy loss to electrons in the ambient target is treated as the dominant effect, with second-order diffusive terms (in both energy and angle) being generally either treated as a small correction or neglected. However, it has recently been pointed out that while neglect of diffusion in energy may indeed be negligible, diffusion in angle is of the same order as deterministic scattering and hence must be included. Here we therefore investigate the effect of angular scattering on the energy deposition profile in the flaring atmosphere. A relatively simple compact expression for the spatial distribution of energy deposition into the ambient plasma is presented and compared with the corresponding deterministic result. For unidirectional injection there is a significant shift in heating from the lower corona to the upper corona; this shift is much smaller for isotropic injection. We also compare the heating profiles due to return current Ohmic heating in the diffusional and deterministic models.

[44]  arXiv:1806.08166 [pdf, other]
Title: Testing Alfvén wave propagation in a realistic set-up of the solar atmosphere
Comments: 17 pages, 8 figures, 1 table and 3 animation links (submitted to the Geophysical and Astrophysical Fluid dynamics special issue- Algorithms and physics of the Pencil code)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Computational Physics (physics.comp-ph)

We present a radiative magneto-hydrodynamic simulation set-up using the Pencil code to study the generation, propagation and dissipation of Alfv\'en waves in the solar atmosphere which includes a convective layer and photosphere below, and the chromosphere, transition region and the corona above. We outline the procedure to prepare the initial state where the solar convection has reached a steady state and the imposed external magnetic field has reached the final value, gradually increasing from a very small initial value. Any new simulation to study Alfv\'en wave propagation can be started from this state which has been thus prepared. We present first results about the nature of waves excited in this simulation run.

[45]  arXiv:1806.08168 [pdf, other]
Title: Design of optical systems with toroidal curved detectors
Comments: 4 pages, 7 figures
Journal-ref: Eduard Muslimov, Emmanuel Hugot, Marc Ferrari, Thibault Behaghel, Gerard R. Lemaitre, Melanie Roulet, and Simona Lombardo, "Design of optical systems with toroidal curved detectors," Opt. Lett. 43, 3092-3095 (2018)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

We consider using toroidal curved detectors to improve the performance of imaging optical systems. We demonstrate that some optical systems have an anamorphic field curvature. We consider an unobscured re-imaging three-mirror anastigmat as an example (f'=960 mm, F/5.3, FoV 4x4 degrees). By assuming that the image is focused on a toroidal detector surface and perform re-optimization, it becomes possible to obtain a notable gain in the image quality - up to 40 % in terms of the spot RMS radius. Through analytic computations and finite-element analysis, we demonstrate that this toroidal shape can be obtained by bending of a thinned detector in a relatively simple setup.

[46]  arXiv:1806.08178 [pdf, other]
Title: Non-Gaussian Features of Primordial Gravitational Waves
Comments: 4 pages, 2 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

We explore possible non-Gaussian features of primordial gravitational waves by constructing model-independent templates for nonlinearity parameters of tensor bispectrum. Our analysis is based on Effective Field Theory of inflation that relies on no particular model as such and thus the results are quite generic. The analysis further reveals that chances of detecting squeezed limit tensor bispectrum are fairly higher than equilateral limit. We also show that by tuning practically one parameter, namely the speed of propagation of primordial gravitational waves, one can have considerably large tensor non-Gaussianities that may be of interest to upcoming CMB missions.

[47]  arXiv:1806.08185 [pdf, ps, other]
Title: On the minimum orbital intersection distance computation: a new effective method
Comments: 13 pages, 10 figures, article accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The computation of the Minimum Orbital Intersection Distance (MOID) is an old, but increasingly relevant problem. Fast and precise methods for MOID computation are needed to select potentially hazardous asteroids from a large catalogue. The same applies to debris with respect to spacecraft. An iterative method that strictly meets these two premises is presented.

[48]  arXiv:1806.08210 [pdf, other]
Title: The evolutionary nature of RV Tauri stars in the SMC and LMC
Comments: 32 Pages, Accepted to be published in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Based on their stellar parameters and the presence of a mid-IR excess due to circumstellar dust, RV Tauri stars have been classified as post-AGB stars. Our recent studies, however, reveal diverse SEDs among RV Tauri stars, suggesting they may occupy other evolutionary channels as well. The aim of this paper is to present the diverse SED characteristics of RV Tauri stars and investigate their evolutionary nature as a function of their SEDs. We carried out a systematic study of RV Tauri stars in the SMC and LMC because of their known distances and hence luminosities. Their SEDs were classified in three groups: dusty (disc-type), non-dusty (non-IR) and uncertain. A period-luminosity- colour (PLC) relation was calibrated. The luminosities from the PLC were complemented with the ones found using their SEDs and the stars were placed on the HR-diagram. The four main results from this study are: 1) RV Tauri stars with a clear IR-excess have disc-type SEDs, which indicates that the dust is trapped in a stable disc. Given the strong link between disc-type SEDs and binarity in the Galaxy, we postulate that these are binaries as well. These cover a range of luminosities and we argue that the more luminous ones are post-AGB stars while the lower luminosity ones are likely post-Red Giant Branch (post-RGB) stars. 2) Two of these objects have variable mean brightness with periods of 916 and 850 days, respectively, caused by variable extinction during orbital motion. 3) The non-dusty RV Tauri stars and the objects with an uncertain SED evolve such that the circumstellar dust has dispersed. If they are single stars, they are post-AGB objects of low initial mass ($<$ 1.25 M$_\odot$), while if they are binaries, the low-luminosity part of the sample are likely post-RGB stars. 4) We find that RV Tauri stars with dust are on average more luminous than the rest of the sample.

[49]  arXiv:1806.08217 [pdf, ps, other]
Title: Fourier analysis of advection-dominated accretion flows
Comments: Accepted for publication in ApJ. Comments welcome
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We implement a new semi-analytical approach to investigate radially self-similar solutions for the steady-state advection-dominated accretion flows (ADAFs). We employ the usual $\alpha$-prescription for the viscosity and all the components of the energy-momentum tensor are considered. In this case, in the spherical coordinate, the problem reduces to a set of eighth-order, nonlinear differential equations with respect to the latitudinal angle $\theta$. Using the Fourier expansions for all the flow quantities, we convert the governing differential equations to a large set of nonlinear algebraic equations for the Fourier coefficients. Using the Newton-Raphson method we solve the algebraic equations and ADAF properties are investigated over a wide range of the model parameters. We also show that the implemented series are truly convergent. The main advantage of our numerical method is that it does not suffer from the usual technical restrictions which may arise for solving ADAF differential equations near to the polar axis. In order to check the reliability of the approach, we recover some widely studied solutions. We also introduce a new varying $\alpha$ viscosity model and new outflow and inflow solutions for ADAFs are presented using Fourier expansion series.

[50]  arXiv:1806.08224 [pdf, ps, other]
Title: A simple analysis of Type I superluminous supernova peak spectra: composition, expansion velocities, and dynamics
Authors: Avishay Gal-Yam
Comments: Final draft, comments welcome
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

We present a simple and well defined prescription to compare absorption lines in supernova (SN) spectra with lists of transitions drawn from the National Institute of Standards and Technology (NIST) database. The method is designed to be applicable to simple spectra where the photosphere can be mostly described by absorptions from single transitions with a single photospheric velocity. These conditions are plausible for SN spectra obtained shortly after explosion. Here we show that the method also works well for spectra of hydrogen-poor (Type I) superluminous supernovae (SLSNe-I) around peak. Analysis of high signal to noise spectra leads to clear identification of numerous spectroscopic features arising from ions of carbon and oxygen, that account for the majority of absorption features detected in the optical range, suggesting the outer envelope of SLSN-I progenitors is dominated by these elements. We find that the prominent absorption features seen in the blue are dominated by numerous lines of OII, as previously suggested, and that the apparent absorption feature widths are dominated by line density and not by doppler broadening. In fact, we find that while the expansion velocities of SLSNe-I around peak are similar to those of normal SNe, the apparent velocity distribution (manifest as the width of single transition features) is much lower (~1500 km/s) indicating emission from a very narrow photosphere in velocity space that is nevertheless expanding rapidly. We inspect the controversial case of ASASSN-15lh, and find that the early spectrum of this object is not consistent with those of SLSNe-I. We also show that SLSNe that initially lack hydrogen features but develop these at late phases, such as iPTF15esb and iPTF16bad, also differ in their early spectra from standard SLSNe-I.

[51]  arXiv:1806.08225 [pdf, other]
Title: Evolutionary paths of binaries with a neutron star. I. The case of SAX J1808.4-3658
Comments: 14 pages, 10 figure, 2 tables
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

The evolutionary status of the low mass X-ray binary SAX J1808.4-3658 is simulated by following the binary evolution of its possible progenitor system through mass transfer, starting at a period of $\sim$6.6 hr. The evolution includes angular momentum losses via magnetic braking and gravitational radiation. It also takes into account the effects of illumination of the donor by both the X-ray emission and the spin down luminosity of the pulsar. The system goes through stages of mass transfer and stages during which it is detached, where only the rotationally powered pulsar irradiates the donor. We show that the pulsar irradiation is a necessary ingredient to reach SAX J1808.4-3658 orbital period when the donor mass is reduced to 0.04 - 0.06 M$_\odot$. We also show that the models reproduce important properties of the system, including the orbital period derivative, which is shown to be directly linked to the evolution through mass transfer cycles. Moreover we find that the effects of the irradiation on the internal structure of the donor are non negligible, causing the companion star to be non completely convective at the values of mass observed for the system and significantly altering its long term evolution, as the magnetic braking remains active along the whole evolution.

[52]  arXiv:1806.08244 [pdf, other]
Title: The importance of binarity in the formation and evolution of planetary nebulae
Authors: David Jones (IAC)
Comments: Submitted Manuscript Under Review: To appear in \textit{The Impact of Binaries on Stellar Evolution}, Beccari G. \& Boffin H.M.J. (Eds.). \copyright\ 2018 Cambridge University Press
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

It is now clear that a binary evolutionary pathway is responsible for a significant fraction of all planetary nebulae, with some authors even going so far as to claim that binarity may be a near requirement for the formation of an observable nebula. In this chapter, we will discuss the theoretical and observational support for the importance of binarity in the formation of planetary nebulae, initially focussing on common envelope evolution but also covering wider binaries. Furthermore, we will highlight the impact that these results have on our understanding of other astrophysical phenomena, including supernovae type Ia, chemically peculiar stars and circumbinary exoplanets. Finally, we will present the latest results with regards to the relationship between post-common-envelope central stars and the abundance discrepancy problem in planetary nebulae, and what further clues this may hold in forwarding our understanding of the common envelope phase itself.

[53]  arXiv:1806.08249 [pdf, other]
Title: What we learn from the X-ray grating spectra of Nova SMC 2016
Comments: Accepted for publication in the Astrophysical Journal, pending final editorial review after "minor changes"
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Nova SMC 2016 has been the most luminous nova known in the direction of the Magellanic Clouds. It turned into a very luminous supersoft X-ray source between day 16 and 28 after the optical maximum. We observed it with Chandra, the HRC-S camera and the Low Energy Transmission Grating (LETG) on 2016 November and 2017 January (days 39 and 88 after optical maximum), and with XMM-Newton on 2016 December (day 75). We detected the compact white dwarf (WD) spectrum as a luminous supersoft X-ray continuum with deep absorption features of carbon, nitrogen, magnesium, calcium, probably argon and sulfur on day 39, and oxygen, nitrogen and carbon on days 75 and 88. The spectral features attributed to the WD atmosphere are all blue-shifted, by about 1800 km/s on day 39 and up to 2100 km/s in the following observations. Spectral lines attributed to low ionization potential transitions in the interstellar medium are also observed. Assuming the distance of the Small Magellanic Cloud, the bolometric luminosity exceeded Eddington level for at least three months. A preliminary analysis with atmospheric models indicates effective temperature around 700,000 K on day 39, peaking at the later dates in the 850,000-900,000 K range, as expected for a 1.25 m(sol) WD. We suggest a possible classification as an oxygen-neon WD, but more precise modeling is needed to accurately determine the abundances. The X-ray light curves show large, aperiodic ux variability, not associated with spectral variability. We detected red noise, but did not find periodic or quasi-periodic modulations.

[54]  arXiv:1806.08255 [pdf, other]
Title: Galaxy And Mass Assembly (GAMA): the signatures of galaxy interactions as viewed from small scale galaxy clustering
Comments: Accepted by MNRAS - 34 figures, 3 tables, 34 pages including 4 appendices
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Statistical studies of galaxy-galaxy interactions often utilise net change in physical properties of progenitors as a function of the separation between their nuclei to trace both the strength and the observable timescale of their interaction. In this study, we use two-point auto, cross and mark correlation functions to investigate the extent to which small-scale clustering properties of star forming galaxies can be used to gain physical insight into galaxy-galaxy interactions between galaxies of similar optical brightness and stellar mass. The Halpha star formers, drawn from the highly spatially complete Galaxy And Mass Assembly (GAMA) survey, show an increase in clustering on small separations. Moreover, the clustering strength shows a strong dependence on optical brightness and stellar mass, where (1) the clustering amplitude of optically brighter galaxies at a given separation is larger than that of optically fainter systems, (2) the small scale clustering properties (e.g. the strength, the scale at which the signal relative to the fiducial power law plateaus) of star forming galaxies appear to differ as a function of increasing optical brightness of galaxies. According to cross and mark correlation analyses, the former result is largely driven by the increased dust content in optically bright star forming galaxies. The latter could be interpreted as evidence of a correlation between interaction-scale and optical brightness of galaxies, where physical evidence of interactions between optically bright star formers, likely hosted within relatively massive halos, persist over larger separations than those between optically faint star formers.

[55]  arXiv:1806.08263 [pdf, other]
Title: High-contrast imaging of HD 163296 with the Keck/NIRC2 L'-band vortex coronograph
Comments: 9 pages, 6 figures. Accepted by MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We present observations of the nearby (D$\sim$100\,pc) Herbig star HD~163296 taken with the vortex coronograph at Keck/NIRC2 in the L' band (3.7~$\mu$m), to search for planetary mass companions in the ringed disc surrounding this pre-main sequence star. The images reveal an arc-like region of scattered light from the disc surface layers that is likely associated with the first bright ring detected with ALMA in the $\lambda$=1.3mm dust continuum at $\sim$65~au. We also detect a point-like source at $\sim$0\farcs5 projected separation in the North-East direction, close to the inner edge of the second gap in the millimetre images. Comparing the point source photometry with the atmospheric emission models of non-accreting giant planets, we obtain a mass of 6--7~M$_J$ for a putative protoplanet, assuming a system age of 5~Myr. Based on the contrast at a 95\% level of completeness calculated on the emission-free regions of our images, we set upper limits for the masses of giant planets of 8--15~M$_J$, 4.5--6.5~M$_J$ and 2.5-4.0~M$_J$ at the locations of the first, second and third gap in the millimetre dust continuum, respectively. Further deep, high resolution thermal IR imaging of the HD~163296 system are warranted, to confirm the presence and nature of the point source and to better understand the structure of the dust disc.

[56]  arXiv:1806.08276 [pdf, other]
Title: The role of spiral arms in Milky Way star formation
Comments: 14 pages, accepted for publication in Monthly Notices of the Royal Astronomical Society
Subjects: Astrophysics of Galaxies (astro-ph.GA)

What role does Galactic structure play in star formation? We have used the Herschel Hi-GAL compact-clump catalogue to examine trends in evolutionary stage over large spatial scales in the inner Galaxy. We examine the relationship between the fraction of clumps with embedded star formation (the star-forming fraction, or SFF) and other measures of star-formation activity. Based on a positive correlation between SFF and evolutionary indicators such as the luminosity-to-mass ratio, we assert that the SFF principally traces the average evolutionary state of a sample and must depend on the local fraction of rapidly-evolving, high-mass young stellar objects. The spiral-arm tangent point longitudes show small excesses in the SFF, though these can be accounted for by a small number of the most massive clusters, just 7.6% of the total number of clumps in the catalogue. This suggests that while the arms tend to be home to the Galaxy's massive clusters, the remaining 92.4% of Hi-GAL clumps in our catalogue do not show an enhancement of star formation within arms. Globally, the SFF is highest at the Galactic midplane and inner longitudes. We find no significant trend in evolutionary stage as a function of position across spiral arms at the tangent-point longitudes. This indicates that the angular offset observed between gas and stars, if coordinated by a density wave, is not evident at the clump phase; alternatively, the onset of star formation is not triggered by the spiral density wave.

[57]  arXiv:1806.08300 [pdf, other]
Title: A precise extragalactic test of General Relativity
Comments: Published in Science. 42 pages, 10 figures including supplementary text and figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc)

Einstein's theory of gravity, General Relativity, has been precisely tested on Solar System scales, but the long-range nature of gravity is still poorly constrained. The nearby strong gravitational lens, ESO 325-G004, provides a laboratory to probe the weak-field regime of gravity and measure the spatial curvature generated per unit mass, $\gamma$. By reconstructing the observed light profile of the lensed arcs and the observed spatially resolved stellar kinematics with a single self-consistent model, we conclude that $\gamma = 0.97 \pm 0.09$ at 68% confidence. Our result is consistent with the prediction of 1 from General Relativity and provides a strong extragalactic constraint on the weak-field metric of gravity.

[58]  arXiv:1806.08305 [pdf, other]
Title: kima: Exoplanet detection in radial velocities
Comments: 3 pages; published in the Journal of Open Source Software; all code available at this https URL
Journal-ref: Journal of Open Source Software, 3(26), 487, 2018
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)

The radial-velocity (RV) method is one of the most successful in the detection of exoplanets, but is hindered by the intrinsic RV variations of the star, which can easily mimic or hide true planetary signals. kima is a package for the detection and characterization of exoplanets using RV data. It fits a sum of Keplerian curves to a timeseries of RV measurements and calculates the evidence for models with a fixed number Np of Keplerian signals, or after marginalising over Np. Moreover, kima can use a GP with a quasi-periodic kernel as a noise model, to deal with activity-induced signals. The hyperparameters of the GP are inferred together with the orbital parameters. The code is written in C++, but includes a helper Python package, pykima, which facilitates the analysis of the results.

[59]  arXiv:1806.08313 [pdf, other]
Title: Nonlinear perturbations from the coupling of the inflaton to a non-Abelian gauge field, with a focus on Chromo-Natural Inflation
Comments: 30 pages, 8 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Several models of inflation employing a triplet of SU(2) vectors with spatially orthogonal vacuum expectation values (VEVs) have been recently proposed. One (tensor) combination $t$ of the vector modes is amplified in some momentum range during inflation. Due to the vector VEVs, this combination mixes with gravitational waves (GW) at the linear level, resulting in a GW amplification that has been well studied in the literature. Scalar perturbations in this class of models have been so far studied only at the linear level. We perform a first step toward the nonlinear computation using as an example the original model of Chromo-Natural Inflation. We compute the contribution to the scalar power spectrum arising from the coupling of the combination $t$ to the inflaton. This contribution is mostly controlled by a single parameter of the model (namely, the ratio between the mass of the fluctuations of the vector field and the Hubble rate), and, for a wide range of this parameter, it can significantly affect the phenomenology obtained from the linear theory. This nonlinear contribution is significantly blue, improving the comparison between the two-point function and the Cosmic Microwave Background (CMB) data. This growth can be also relevant for smaller scale phenomenology, such as large scale structure, CMB distortions, and primordial black holes.

[60]  arXiv:1806.08322 [pdf, other]
Title: Characterization of Stellar and Substellar Members in the Coma Berenices Star Cluster
Comments: Accepted by Astrophysical Journal
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

We have identified stellar and substellar members in the nearby star cluster Coma Berenices, using photometry, proper motions, and distances of a combination of 2MASS, UKIDSS, URAT1, and {\it Gaia}/DR2 data. Those with {\it Gaia}/DR2 parallax measurements provide the most reliable sample to constrain the distance, averaging 86.7~pc with a dispersion 7.1~pc, and the age $\sim800$~Myr, of the cluster. This age is older than the 400--600~Myr commonly adopted in the literature. Our analysis, complete within 5deg of the cluster radius, leads to identification of 192 candidates, among which, after field contamination is considered, about 148 are true members. The members have $J\sim3$~mag to $\sim17.5$~mag, corresponding to stellar masses 2.3--0.06~$M_\odot$. The mass function of the cluster peaks around 0.3~$M_\odot$ and, in the sense of $dN/dm = m^{-\alpha}$, where $N$ is the number of members and $m$ is stellar mass, has a slope $\alpha\approx 0.49\pm0.03$ in the mass range 0.3--2.3~$M_\odot$. This is much shallower than that of the field population in the solar neighborhood. The slope $\alpha=-1.69\pm0.14$ from 0.3~$M_\odot$ to 0.06~$M_\odot$, the lowest mass in our sample. The cluster is mass segregated and has a shape elongated toward the Galactic plane. Our list contains nine substellar members, including three new discoveries of an M8, an L1 and an L4 brown dwarfs, extending from the previously known coolest members of late-M types to even cooler types.

[61]  arXiv:1806.08339 [pdf, other]
Title: Weak gravitational lensing with CO galaxies
Comments: Contribution to 2018, ASP Conference Series Monograph 7, "Science with a Next-Generation Very Large Array," Eric Murphy, ed., in preparation
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Optical weak lensing surveys have become a powerful tool for precision cosmology, but remain subject to systematic effects that can severely bias cosmological parameter estimates if not carefully removed. We discuss the possibility of performing complementary weak lensing surveys at radio/microwave frequencies, using detections of CO-emitting galaxies with resolved continuum images from ngVLA. This method has completely different systematic uncertainties to optical weak lensing shear measurements (e.g. in terms of blending, PSF, and redshift uncertainties), and can provide additional information to help disentangle intrinsic alignments from the cosmological shear signal. A combined analysis of optical and CO galaxy lensing surveys would therefore provide an extremely stringent validation of highly-sensitive future surveys with Euclid, LSST, and WFIRST, definitively rejecting biases due to residual systematic effects. A lensing survey on ngVLA would also provide valuable spectral (kinematic) and polarimetric information, which can be used to develop novel cosmological analyses that are not currently possible in the optical.

[62]  arXiv:1806.08343 [pdf, other]
Title: Signatures of an eruptive phase before the explosion of the peculiar core-collapse SN 2013gc
Comments: 21 pages, 13 figures, 8 tables, submitted to MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

We present photometric and spectroscopic analysis of the peculiar core-collapse SN 2013gc. The light curve shows an early maximum followed by a fast decline and a phase of almost constant luminosity. At 200 days from maximum, a brightening of 1 mag is observed in all bands, followed by a steep linear luminosity decline after 300 d. From archival images taken between 1.5 and 2.5 years before the explosion, we found that a weak source is visible at the supernova location, with mag 20. The early supernova spectra show Balmer lines, with a narrow (560 km/s) P-Cygni absorption superimposed on a broad (3400 km/s) component, typical of type IIn events. Through a comparison of colour curves, absolute light curves and spectra of SN 2013gc with a sample of supernovae IIn, we conclude that SN 2013gc is a member of the so-called type IId subgroup (Benetti 2000). The complex profile of the Halpha line suggests a composite circumstellar medium geometry, with a combination of lower velocity, spherically symmetric gas and a more rapidly expanding bilobed feature. This distribution of the circumstellar medium has been likely formed through major mass-loss events, that we directly observed from 3 years before the explosion of SN 2013gc. The modest luminosity of SN 2013gc at all phases, the very small amount of ejected 56Ni (of the order of 10^-3 M_sun), the major pre-supernova stellar activity and the lack of prominent [O I] lines in the late-time spectra support a fall-back core-collapse scenario for the massive progenitor of SN 2013gc.

Cross-lists for Fri, 22 Jun 18

[63]  arXiv:1806.07909 (cross-list from gr-qc) [pdf, other]
Title: Black hole binaries: ergoregions, photon surfaces, wave scattering, and quasinormal modes
Comments: 13 pages, 11 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th); Fluid Dynamics (physics.flu-dyn)

The photon surface of isolated black holes is related to important aspects of black hole physics, such as strong lensing, absorption cross section of null particles and the way that black holes relax through quasinormal ringing. When two black holes are present -- such as during the inspiral and merger events of interest for gravitational-wave detectors -- the concept of a photon surface still exists, but its properties are basically unknown. With these applications in mind, we study here the photon surface of two different static black hole binaries. The first one is the Majumdar-Papapetrou geometry describing two extremal, charged black holes in equilibrium, while the second one is the double sink solution of fluid dynamics, which describes (in a curved-spacetime language) two "dumb" holes. For the latter solution, we also characterize its dynamical response to external perturbations, and study how it relates to the photon surface structure. In addition, we compute the ergoregion of such spacetime and show that it does not coincide with the event horizon.

[64]  arXiv:1806.08157 (cross-list from physics.plasm-ph) [pdf, other]
Title: Resistively-limited current sheet implosions in planar anti-parallel (1D) and null-point containing (2D) magnetic field geometries
Comments: Accepted, will be published Open Access in Physics of Plasmas - refer to main journal for animations
Subjects: Plasma Physics (physics.plasm-ph); Solar and Stellar Astrophysics (astro-ph.SR); Fluid Dynamics (physics.flu-dyn)

Implosive formation of current sheets is a fundamental plasma process. Previous studies focused on the early time evolution, while here our primary aim is to explore the longer-term evolution, which may be critical for determining the efficiency of energy release. To address this problem we investigate two closely-related problems, namely: (i) 1D, pinched anti-parallel magnetic fields and (ii) 2D, null point containing fields which are locally imbalanced ('null-collapse' or 'X-point collapse'). Within the framework of resistive MHD, we simulate the full nonlinear evolution through three distinct phases: the initial implosion, its eventual halting mechanism, and subsequent evolution post-halting. In a parameter study, we find the scaling with resistivity of current sheet properties at the halting time is in good agreement - in both geometries - with that inferred from a known 1D similarity solution. We find that the halting of the implosions occurs rapidly after reaching the diffusion scale by sudden Ohmic heating of the dense plasma within the current sheet, which provides a pressure gradient sufficient to oppose further collapse and decelerate the converging flow. This back-pressure grows to exceed that required for force balance and so the post-implosion evolution is characterised by the consequences of the current sheet `bouncing' outwards. These are: (i) the launching of propagating fast MHD waves (shocks) outwards and (ii) the width-wise expansion of the current sheet itself. The expansion is only observed to stall in the 2D case, where the pressurisation is relieved by outflow in the reconnection jets. In the 2D case, we quantify the maximum amount of current sheet expansion as it scales with resistivity, {and analyse the structure of the reconnection region which forms post-expansion, replete with Petschek-type slow shocks and fast termination shocks.

Replacements for Fri, 22 Jun 18

[65]  arXiv:1702.04526 (replaced) [pdf, other]
Title: Sterile neutrino dark matter from right-handed neutrino oscillations
Comments: Version to appear in PRD
Journal-ref: Phys. Rev. D 97, 115021 (2018)
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[66]  arXiv:1707.09578 (replaced) [pdf, other]
Title: Primordial black holes and second order gravitational waves from ultra-slow-roll inflation
Comments: add the discussion of second order gravitational waves, accepted for publication in JCAP
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
[67]  arXiv:1708.06291 (replaced) [pdf, ps, other]
Title: Detectability of 21cm-signal during the Epoch of Reionization with 21cm-Lyman-$α$ emitter cross-correlation. I
Comments: 13pages, 13figures, 3tables, accepted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[68]  arXiv:1709.01943 (replaced) [pdf, other]
Title: Explaining LIGO's observations via isolated binary evolution with natal kicks
Authors: D. Wysocki (1), D. Gerosa (2), R. O'Shaughnessy (1), K. Belczynski (3), W. Gladysz (4), E. Berti (5,6), M. Kesden (7), D. Holz (8) ((1) Rochester Institute of Technology, (2) Caltech, (3) Nicolaus Copernicus Astronomical Centre, Warsaw, (4) Warsaw University, (5) University of Mississippi, (6) CENTRA)
Comments: 19 pages, 14 figures, as published in PRD
Journal-ref: Phys. Rev. D 97, 043014 (2018)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
[69]  arXiv:1712.00677 (replaced) [pdf, other]
Title: The $H_0$ and $σ_8$ tensions and the scale invariant spectrum
Comments: 10 pages
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[70]  arXiv:1712.06799 (replaced) [pdf, ps, other]
Title: The Difference in Abundances between N-bearing and O-bearing Species in High-Mass Star-Forming Regions
Comments: Accepted to ApJS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
[71]  arXiv:1801.03104 (replaced) [pdf, other]
Title: Physical properties and scaling relations of molecular clouds: the effect of stellar feedback
Comments: 12 pages, 8 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[72]  arXiv:1801.03585 (replaced) [pdf, other]
Title: Indications of an unexpected signal associated with the GW170817 binary neutron star inspiral
Comments: 11 pages, 3 figures (minor edits and reformatting to bring it closer to the published version)
Journal-ref: Astroparticle Physics 103 (2018) 1-6
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)
[73]  arXiv:1801.06222 (replaced) [pdf, other]
Title: Pushing back the limits: detailed properties of dwarf galaxies in a LCDM universe
Authors: Yves Revaz (1), Pascale Jablonka (1) ((1) EPFL)
Comments: 22 pages, 13 figures, accepted in A&A. Movies of the simulations are available here : this https URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[74]  arXiv:1802.00014 (replaced) [pdf, other]
Title: The MASSIVE Survey - X. Misalignment between Kinematic and Photometric Axes and Intrinsic Shapes of Massive Early-Type Galaxies
Comments: Accepted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[75]  arXiv:1803.00461 (replaced) [pdf, other]
Title: Modeling the evolution and propagation of the 2017 September 9th and 10th CMEs and SEPs arriving at Mars constrained by remote-sensing and in-situ measurement
Subjects: Space Physics (physics.space-ph); Earth and Planetary Astrophysics (astro-ph.EP)
[76]  arXiv:1803.01722 (replaced) [pdf, other]
Title: Distortion of the standard cosmology in R+R^2 theory
Comments: 22 pages, 10 figures. Several references and clarifying comments are added
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[77]  arXiv:1803.05300 (replaced) [pdf, ps, other]
Title: Accelerating infall and rotational spin-up in the hot molecular core G31.41+0.31
Authors: M. T. Beltrán (1), R. Cesaroni (1), V.M. Rivilla (1), Á. Sánchez-Monge (2), L. Moscadelli (1), A. Ahmadi (3), V. Allen (4, 5), H. Beuther (3), S. Etoka (6), D. Galli (1), R. Galván-Madrid (7), C. Goddi (8, 9), K.G. Johnston (11), A. Kölligan (12), R. Kuiper (12), M. S.N. Kumar (13, 14), L.T. Maud (15, 9), J.C. Mottram (3), T. Peters (16), P. Schilke (2), L. Testi (1, 17), F. van der Tak (4, 5), C. M. Walmsley ((1) INAF-Osservatorio Astrofisico di Arcetri, (2) I. Physikalisches Institut, Universität zu Köln, (3) Max Planck Institute for Astronomy, Heidelberg, (4) Kapteyn Astronomical Institute, University of Groningen, (5) SRON Netherlands Institute for Space Research, Groningen, (6) Jodrell Bank Centre for Astrophysics, Manchester, (7) Instituto de Radioastronomía y Astrofísica Morelia, (8) Department of Astrophysics/IMAPP, Radboud University, (9) ALLEGRO/Leiden Observatory, Leiden University, (10) School of Physics and Astronomy, Leeds, (11) UK Astronomy Technology Centre, Royal Observatory Edinburgh, (12) Institute of Astronomy and Astrophysics, University of Tübingen, (13) Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, (14) Centre for Astrophysics, University of Hertfordshire, (15) Leiden Observatory, Leiden University, (16) Max-Planck-Institut für Astrophysik, Garching, (17) ESO)
Comments: 28 pages, 16 figures, and 7 tables. Accepted for publication in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
[78]  arXiv:1803.07637 (replaced) [pdf, other]
Title: The Applegate mechanism in Post-Common-Envelope Binaries: Investigating the role of rotation
Comments: 9 pages, 5 figures. Accepted for publication in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[79]  arXiv:1803.08049 (replaced) [pdf, ps, other]
Title: BCG Mass Evolution in Cosmological Hydro-Simulations
Comments: 13 pages, 10 figures, Accepted by MNRAS 2018 June 17
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[80]  arXiv:1804.03479 (replaced) [pdf, other]
Title: Magnetohydrodynamics with GAMER
Comments: 29 pages, 22 figures, 1 table. GAMER-MHD will soon become available at this https URL
Journal-ref: The Astrophysical Journal supplement series, 236, 50, 2018
Subjects: Computational Physics (physics.comp-ph); Instrumentation and Methods for Astrophysics (astro-ph.IM)
[81]  arXiv:1804.08249 (replaced) [pdf, ps, other]
Title: Improving the absolute accuracy of the gravitational wave detectors by combining the photon pressure and gravity field calibrators
Comments: 15 pages, 8 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
[82]  arXiv:1804.09064 (replaced) [pdf, other]
Title: An introductory study to white dwarfs
Comments: 5 pages, 6 figures. Poster presented at the XIV International Workshop on Hadron Physics, Florianopolis, Brazil, March 2018
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[83]  arXiv:1804.09368 (replaced) [pdf, other]
Title: Gaia Data Release 2: Photometric content and validation
Comments: This version has corrections to Appendix A. All the SDSS transformations have been corrected. Tables A.1 and A.2 have changed for the SDSS relationships. Three of the subfigures in Figure A.1 have changed. The author list has been expanded
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
[84]  arXiv:1805.02476 (replaced) [pdf, other]
Title: Unlocking the secrets of the midplane gas and dust distribution in the young hybrid disc HD 141569
Comments: 5 pages, 3 figures, Accepted for publication in A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[85]  arXiv:1805.08773 (replaced) [pdf, other]
Title: Exploring compensated isocurvature perturbations with CMB spectral distortion anisotropies
Comments: 26 pages, 4 figures; v2: numerical calculation corrected, constraints changed
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
[86]  arXiv:1806.05277 (replaced) [pdf, other]
Title: The phase-polarization curve of asteroid (3200) Phaethon
Comments: 12 pages, 7 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[87]  arXiv:1806.07361 (replaced) [pdf, ps, other]
Title: Comparing the emission spectra of U and Th hollow cathode lamps and a new U line-list
Comments: 14 pages, 20 figures, line list available online. Version 2 includes the link to the online U line-list
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
[88]  arXiv:1806.07707 (replaced) [pdf, other]
Title: Chemistry in disks. XI. Sulfur-bearing species as tracers of protoplanetary disk physics and chemistry: the DM Tau case
Authors: D. Semenov (1, 2), C. Favre (3), D. Fedele (3), S. Guilloteau (4, 5), R. Teague (6), Th. Henning (1), A. Dutrey (4, 5), E. Chapillon (7), F. Hersant (4, 5), V. Piétu (7)
Comments: Accepted by Astronomy & Astrophysics (15 pages, 15 figures, 8 tables)
Subjects: Astrophysics of Galaxies (astro-ph.GA); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
[89]  arXiv:1806.07827 (replaced) [pdf, other]
Title: Molecular gas and star formation in an absorption-selected galaxy: Hitting the bull's eye at z = 2.46
Comments: accepted for publication in A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA)
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