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Astrophysics

New submissions

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New submissions for Mon, 19 Feb 18

[1]  arXiv:1802.05712 [pdf, other]
Title: Gravitational waves from vacuum first-order phase transitions: from the envelope to the lattice
Comments: 15 pages, 15 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

We conduct large scale numerical simulations of gravitational wave production at a first order vacuum phase transition. We find a power law for the gravitational wave power spectrum at high wavenumber which falls off as $k^{-1.5}$ rather than the $k^{-1}$ produced by the envelope approximation. The peak of the power spectrum is shifted to slightly lower wave numbers from that of the envelope approximation. The envelope approximation reproduces our results for the peak power less well, agreeing only to within an order of magnitude. After the bubbles finish colliding the scalar field oscillates around the true vacuum. An additional feature is produced in the UV of the gravitational wave power spectrum, and this continues to grow linearly until the end of our simulation. The additional feature peaks at a length scale close to the bubble wall thickness and is shown to have a negligible contribution to the energy in gravitational waves, providing the scalar field mass is much smaller than the Planck mass.

[2]  arXiv:1802.05715 [pdf, other]
Title: An image-based array trigger for Imaging Atmospheric Cherenkov Telescope Arrays
Comments: 22 pages, 12 figures. Accepted for publication in NIMA
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

It is anticipated that forthcoming, next generation, atmospheric Cherenkov telescope arrays will include a number of medium-sized telescopes that are constructed using a dual-mirror Schwarzschild-Couder configuration. These telescopes will sample a wide ($8^{\circ}$) field of view using a densely pixelated camera comprising over $10^{4}$ individual readout channels. A readout frequency congruent with the expected single-telescope trigger rates would result in substantial data rates. To ameliorate these data rates, a novel, hardware-level Distributed Intelligent Array Trigger (DIAT) is envisioned. A copy of the DIAT operates autonomously at each telescope and uses reduced resolution imaging data from a limited subset of nearby telescopes to veto events prior to camera readout {and any subsequent network transmission of camera data that is required for centralized storage or aggregation}. We present the results of Monte-Carlo simulations that evaluate the efficacy of a "Parallax width" discriminator that can be used by the DIAT to efficiently distinguish between genuine gamma-ray initiated events and unwanted background events that are initiated by hadronic cosmic rays.

[3]  arXiv:1802.05716 [pdf, ps, other]
Title: Secular dynamics of hierarchical multiple systems composed of nested binaries, with an arbitrary number of bodies and arbitrary hierarchical structure. II. External perturbations: flybys and supernovae
Authors: Adrian S. Hamers
Comments: Accepted for publication in MNRAS. 24 pages, 7 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

We extend the formalism of a previous paper to include the effects of flybys and instantaneous perturbations such as supernovae on the long-term secular evolution of hierarchical multiple systems with an arbitrary number of bodies and hierarchy, provided that the system is composed of nested binary orbits. To model secular encounters, we expand the Hamiltonian in terms of the ratio of the separation of the perturber with respect to the barycentre of the multiple system, to the separation of the widest orbit. Subsequently, we integrate over the perturber orbit numerically or analytically. We verify our method for secular encounters, and illustrate it with an example. Furthermore, we describe a method to compute instantaneous orbital changes to multiple systems, such as asymmetric supernovae and impulsive encounters. The secular code, with implementation of the extensions described in this paper, is publicly available within AMUSE, and we provide a number of simple example scripts to illustrate its usage for secular and impulsive encounters, and asymmetric supernovae. The extensions presented in this paper are a next step toward efficiently modeling the evolution of complex multiple systems embedded in star clusters.

[4]  arXiv:1802.05717 [pdf, other]
Title: A model for AGN variability on multiple timescales
Comments: 5 pages, 2 figures, letter accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

We present a framework to link and describe AGN variability on a wide range of timescales, from days to billions of years. In particular, we concentrate on the AGN variability features related to changes in black hole fuelling and accretion rate. In our framework, the variability features observed in different AGN at different timescales may be explained as realisations of the same underlying statistical properties. In this context, we propose a model to simulate the evolution of AGN light curves with time based on the probability density function (PDF) and power spectral density (PSD) of the Eddington ratio ($L/L_{\rm Edd}$) distribution. Motivated by general galaxy population properties, we propose that the PDF may be inspired by the $L/L_{\rm Edd}$ distribution function (ERDF), and that a single (or limited number of) ERDF+PSD set may explain all observed variability features. After outlining the framework and the model, we compile a set of variability measurements in terms of structure function (SF) and magnitude difference. We then combine the variability measurements on a SF plot ranging from days to Gyr. The proposed framework enables constraints on the underlying PSD and the ability to link AGN variability on different timescales, therefore providing new insights into AGN variability and black hole growth phenomena.

[5]  arXiv:1802.05720 [pdf, other]
Title: Obscured star-formation in bright z ~ 7 Lyman-break galaxies
Comments: 12 pages, 6 figure, 3 tables
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present Atacama Large Millimeter/Submillimeter Array observations of the rest-frame far-infrared (FIR) dust continuum emission of six bright Lyman-break galaxies (LBGs) at $z \simeq 7$. The average FIR luminosity of the sample is found to be $L_{\rm FIR} \simeq 2 \times 10^{11}\,{\rm L}_{\odot}$, corresponding to an obscured star-formation rate (SFR) that is comparable to that inferred from the unobscured UV emission. In comparison to the infrared excess (IRX$\,=L_{\rm FIR}/L_{\rm UV}$)-$\beta$ relation, our results are consistent with a Calzetti-like attenuation law (assuming a dust temperature of T = 40-50 K). We find a physical offset of 3 kpc between the dust continuum emission and the rest-frame UV light probed by Hubble Space Telescope imaging for galaxy ID65666 at $z = 7.17^{+0.09}_{-0.06}$. The offset is suggestive of an inhomogeneous dust distribution, where 75% of the total star formation activity (SFR$ \,\simeq 70\,{\rm M}_{\odot}/{\rm yr}$) of the galaxy is completely obscured. Our results provide direct evidence that dust obscuration plays a key role in shaping the bright-end of the observed rest-frame UV luminosity function at $z \simeq 7$, in agreement with cosmological galaxy formation simulations. The existence of a heavily-obscured component of galaxy ID65666 indicates that dusty star-forming regions, or even entire galaxies, that are "UV-dark" are significant even in the $z \simeq 7$ galaxy population.

[6]  arXiv:1802.05725 [pdf, ps, other]
Title: A New Catalogue of Galactic Novae: Investigation of the MMRD relation & Spatial Distribution
Comments: 24 pages, 9 figures, 6 tables; Accepted for publication in MNRAS on 13 Feb 2018
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

In this study, a new Galactic novae catalogue is introduced collecting important parameters of these sources such as their light curve parameters, classifications, full width half maximum (FWHM) of H$_\alpha$ line, distances and interstellar reddening estimates. The catalogue is also published on a website with a search option via a SQL query and an online tool to re-calculate the distance/reddening of a nova from the derived reddening-distance relations. Using the novae in the catalogue, the existence of a maximum magnitude-rate of decline (MMRD) relation in the Galaxy is investigated. Although an MMRD relation was obtained, a significant scattering in the resulting MMRD distribution still exists. We suggest that the MMRD relation likely depends on other parameters in addition to the decline time, as FWHM H$_\alpha$, the light curve shapes. Using two different samples depending on the distances in the catalogue and from the derived MMRD relation, the spatial distributions of Galactic novae as a function of their spectral and speed classes were studied. The investigation on the Galactic model parameters implies that best estimates for the local outburst density are 3.6 and 4.2 $\times 10^{-10}$ pc$^{-3}$ yr$^{-1}$ with a scale height of 148 and 175 pc, while the space density changes in the range of $0.4 - 16 \ \times 10^{-6}$ pc$^{-3}$. The local outburst density and scale height obtained in this study infer that the disk nova rate in the Galaxy is in the range of $\sim20$ to $\sim100$ yr$^{-1}$ with an average estimate $67^{+21}_{-17}$ yr$^{-1}$.

[7]  arXiv:1802.05736 [pdf, other]
Title: Impact of Gas Giant Instabilities on Habitable Planets
Authors: Sonja Seppeur
Comments: 12 pages, 15 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The detection of many extrasolar gas giants with high eccentricities indicates that dynamical instabilities in planetary systems are common. These instabilities can alter the orbits of gas giants as well as the orbits of terrestrial planets and therefore eject or move a habitable planet out of the habitable zone. In this work 423 simulations with 153 different hypothetical planetary systems with gas giants and terrestrial planets have been modelled to explore the orbital stability of habitable planets. The initial parameter variations include the number, distances and masses of the giant planets and the star type. Linear correlations between the initial number and the initial distances of gas giants and the survival rate of habitable planets were found. Planetary systems consisting of two giant planets are fairly benign to terrestrial planets, whereas six giant planets very often lead to a complete clearing of the habitable zone. Systems with initial distances of five Hill Radii between the giant planets have a high chance to harbour a habitable planet, although more compact systems are very destructive. The giant planet masses have a smaller impact on the stability of habitable worlds. Additionally, a link between the present-day orbit of an observed giant exoplanet and the survival rate of habitable planets was established. As a rule of thumb, observed gas giants with eccentricities higher than 0.4 and inclinations higher than 20 degrees have experienced strong planet-planet scatterings and are unlikely to have a habitable planet in its system. Furthermore, it was found that habitable planets surrounding a K or M-star have a higher survival rate than those surrounding a G-star.

[8]  arXiv:1802.05738 [pdf, other]
Title: The spin of the second-born black hole in coalescing binary black holes
Comments: 20 pages, 15 figures; submitted to A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics - Phenomenology (hep-ph)

Various binary black hole formation channels have been proposed since the first gravitational event GW150914 was discovered by the Advanced Laser Interferometer Gravitational-Wave Observatory (AdLIGO). For all evolutionary channels based on the evolution of isolated binaries, the immediate progenitor of the binary black hole is a close binary system composed of a black hole and a helium star. We perform detailed binary evolution and systematically explore the parameter space of initial binary properties, including initial black hole and helium star masses, initial rotation of the helium star as well as metallicity. We argue that the spin of the first-born black hole at its birth is negligible ($\lesssim 0.1$), hence the second-born black hole's spin dominates the measured effective spin, $\chi_{\rm eff}$, from gravitational wave events of double black hole mergers. We find that tides can be important only when orbital periods are shorter than 2 days. Upon core collapse, the helium star produces a black hole (the second-born black hole in the system) with a spin that can span the entire range from zero to maximally spinning. We show that the bimodal distribution of the spin of the second-born black hole obtained in recent papers is mainly due to oversimplifying assumptions. We find an anti-correlation between the merging timescale of the two black holes, T$_{\rm merger}$, and the effective spin $\chi_{\rm eff}$. Finally, we provide new prescriptions for the tidal coefficient E$_2$ for both H-rich and the helium-rich stars. We predict that, with future improvements to AdLIGO's sensitivity, the sample of merging binary black hole systems will show an overdensity of sources with positive but small $\chi_{\rm eff}$. originating from lower mass black hole mergers born at low redshift.

[9]  arXiv:1802.05742 [pdf, ps, other]
Title: Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) III. Star formation properties of the host galaxies at $z \gtrsim 6$ studied with ALMA
Comments: 20 pages, 9 figures, 4 tables. Accepted for publication in PASJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present our ALMA Cycle 4 measurements of the [CII] emission line and the underlying far-infrared (FIR) continuum emission from four optically low-luminosity ($M_{\rm 1450} > -25$) quasars at $z \gtrsim 6$ discovered by the Subaru Hyper Suprime Cam (HSC) survey. The [CII] line and FIR continuum luminosities lie in the ranges $L_{\rm [CII]} = (3.8-10.2) \times 10^8~L_\odot$ and $L_{\rm FIR} = (1.2-2.0) \times 10^{11}~L_\odot$, which are at least one order of magnitude smaller than those of optically-luminous quasars at $z \gtrsim 6$. We estimate the star formation rates (SFR) of our targets as $\simeq 23-40~M_\odot ~{\rm yr}^{-1}$. Their line and continuum-emitting regions are marginally resolved, and found to be comparable in size to those of optically luminous quasars, indicating that their SFR or likely gas mass surface densities (key controlling parameter of mass accretion) are accordingly different. The $L_{\rm [CII]}/L_{\rm FIR}$ ratios of the hosts, $\simeq (2.2-8.7) \times 10^{-3}$, are fully consistent with local star-forming galaxies. Using the [CII] dynamics, we derived their dynamical masses within a radius of 1.5-2.5 kpc as $\simeq (1.4-8.2) \times 10^{10}~M_\odot$. By interpreting these masses as stellar ones, we suggest that these faint quasar hosts are on or even below the star-forming main sequence at $z \sim 6$, i.e., they appear to be transforming into quiescent galaxies. This is in contrast to the optically luminous quasars at those redshifts, which show starburst-like properties. Finally, we find that the ratios of black hole mass to host galaxy dynamical mass of the most of low-luminosity quasars including the HSC ones are consistent with the local value. The mass ratios of the HSC quasars can be reproduced by a semi-analytical model that assumes merger-induced black hole-host galaxy evolution.

[10]  arXiv:1802.05760 [pdf, ps, other]
Title: The mid-infrared properties and gas content of active galaxies over large look-back times
Comments: Accepted by MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Upon an expansion of all of the searches for redshifted HI 21-cm absorption (0.0021 < z 5.19), we update recent results regarding the detection of 21-cm in the non-local Universe. Specifically, we confirm that photo-ionisation of the gas is the mostly likely cause of the low detection rate at high redshift, in addition to finding that at z < 0.1 there may also be a decrease in the detection rate, which we suggest is due to the dilution of the absorption strength by 21-cm emission. By assuming that associated and intervening absorbers have similar cosmological mass densities, we find evidence that the spin temperature of the gas evolves with redshift, consistent with heating by ultra-violet photons. From the near--infrared (3.4, 4.6 and 12 micron) colours, we see that radio galaxies become more quasar-like in their activity with increasing redshift. We also find that the non-detection of 21-cm absorption at high redshift is not likely to be due to the selection of gas-poor ellipticals, in addition to a strong correlation between the ionising photon rate and the [3.4] - [4.6] colour, indicating that the UV photons arise from AGN activity. Like previous studies, we find a correlation between the detection of 21-cm absorption and the [4.6] - [12] colour, which is a tracer of star-forming activity. However, this only applies at the lowest redshifts (z < 0.1), the range considered by the other studies.

[11]  arXiv:1802.05764 [pdf, other]
Title: Characterization of methanol as a magnetic field tracer in star-forming regions
Comments: 23 pages, 3 figures, excluding Supplementary information. Author manuscript version before editorial/copyediting by Nature Astronomy. Journal version available via this http URL . Supplementary material available via this https URL
Journal-ref: Nature Astronomy (2018)
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

Magnetic fields play an important role during star formation. Direct magnetic field strength observations have proven specifically challenging in the extremely dynamic protostellar phase. Because of their occurrence in the densest parts of star forming regions, masers, through polarization observations, are the main source of magnetic field strength and morphology measurements around protostars. Of all maser species, methanol is one of the strongest and most abundant tracers of gas around high-mass protostellar disks and in outflows. However, as experimental determination of the magnetic characteristics of methanol has remained largely unsuccessful, a robust magnetic field strength analysis of these regions could hitherto not be performed. Here we report a quantitative theoretical model of the magnetic properties of methanol, including the complicated hyperfine structure that results from its internal rotation. We show that the large range in values of the Land\'{e} g-factors of the hyperfine components of each maser line lead to conclusions which differ substantially from the current interpretation based on a single effective g-factor. These conclusions are more consistent with other observations and confirm the presence of dynamically important magnetic fields around protostars. Additionally, our calculations show that (non-linear) Zeeman effects must be taken into account to further enhance the accuracy of cosmological electron-to-proton mass ratio determinations using methanol.

[12]  arXiv:1802.05783 [pdf, other]
Title: Superresolution Interferometric Imaging with Sparse Modeling Using Total Squared Variation --- Application to Imaging the Black Hole Shadow
Comments: 18 pages, 7 figures, submitted to ApJ, revised in Feb 2018
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

We propose a new superresolution imaging technique for interferometry using sparse modeling, utilizing two regularization terms: the $\ell_1$-norm and a new function named Total Squared Variation (TSV) of the brightness distribution. TSV is an edge-smoothing variant of Total Variation (TV), leading to reducing the sum of squared gradients. First, we demonstrate that our technique may achieve super-resolution of $\sim 30$% compared to the traditional CLEAN beam size using synthetic observations of two point sources. Second, we present simulated observations of three physically motivated static models of Sgr A* with the Event Horizon Telescope (EHT) to show the performance of proposed techniques in greater detail. We find that $\ell_1$+TSV regularization outperforms $\ell_1$+TV regularization with the popular isotropic TV term and the Cotton-Schwab CLEAN algorithm, demonstrating that TSV is well-matched to the expected physical properties of the astronomical images, which are often nebulous. Remarkably, in both the image and gradient domains, the optimal beam size minimizing root-mean-squared errors is $\lesssim 10$% of the traditional CLEAN beam size for $\ell_1$+TSV regularization, and non-convolved reconstructed images have smaller errors than beam-convolved reconstructed images. This indicates that the traditional post-processing technique of Gaussian convolution in interferometric imaging may not be required for the $\ell_1$+TSV regularization. We also propose a feature extraction method to detect circular features from the image of a black hole shadow with the circle Hough transform (CHT) and use it to evaluate the performance of the image reconstruction. With our imaging technique and the CHT, the EHT can constrain the radius of the black hole shadow with an accuracy of $\sim 10-20$% in present simulations for Sgr A*.

[13]  arXiv:1802.05805 [pdf, ps, other]
Title: OSSOS IX: two objects in Neptune's 9:1 resonance -- implications for resonance sticking in the scattering population
Comments: submitted to AAS journals
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We discuss the detection in the Outer Solar System Origins Survey (OSSOS) of two objects in Neptune's distant 9:1 mean motion resonance at semimajor axis $a\approx 130$~au. Both objects are securely resonant on 10 Myr timescales, with one securely in the 9:1 resonance's leading asymmetric libration island and the other in either the symmetric or trailing asymmetric island. These two objects are the largest semimajor axis objects known with secure resonant classifications, and their detection in a carefully characterized survey allows for the first robust population estimate for a resonance beyond 100~au. The detection of these two objects implies a population in the 9:1 resonance of $1.1\times10^4$ objects with $H_r<8.66$ ($D \gtrsim 100$~km) on similar orbits, with 95\% confidence range of $\sim0.4-3\times10^4$. Integrations over 4 Gyr of an ensemble of clones chosen from within the orbit fit uncertainties for these objects reveal that they both have median resonance occupation timescales of $\sim1$~Gyr. These timescales are consistent with the hypothesis that these two objects originate in the scattering population but became transiently stuck to Neptune's 9:1 resonance within the last $\sim1$~Gyr of solar system evolution. Based on simulations of a model of the current scattering population, we estimate the expected resonance sticking population in the 9:1 resonance to be 1000--5000 objects with $H_r<8.66$; this is marginally consistent with the OSSOS 9:1 population estimate. We conclude that resonance sticking is a plausible explanation for the observed 9:1 population, but we also discuss the possibility of a primordial 9:1 population, which would have interesting implications for the Kuiper belt's dynamical history.

[14]  arXiv:1802.05806 [pdf, other]
Title: Duty-cycle and energetics of remnant radio-loud AGN
Authors: Ross J. Turner
Comments: 9 pages, 5 figures, 1 table; accepted in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Deriving the energetics of remnant and restarted active galactic nuclei (AGNs) is much more challenging than for active sources due to the complexity in accurately determining the time since the nucleus switched-off. I resolve this problem using a new approach that combines spectral ageing and dynamical models to tightly constrain the energetics and duty-cycles of dying sources. Fitting the shape of the integrated radio spectrum yields the fraction of the source age the nucleus is active; this, in addition to the flux density, source size, axis ratio, and properties of the host environment, provides a constraint on dynamical models describing the remnant radio source. This technique is used to derive the intrinsic properties of the well-studied remnant radio source B2 0924+30. This object is found to spend $50^{+14}_{-12}$ Myr in the active phase and a further $28^{+6}_{-5}$ Myr in the quiescent phase, have a jet kinetic power of $3.6^{+3.0}_{-1.7}\times 10^{37}$ W, and a lobe magnetic field strength below equipartition at the $8\sigma$ level. The integrated spectra of restarted and intermittent radio sources is found to yield a 'steep-shallow' shape when the previous outburst occurred within 100 Myr. The duty-cycle of B2 0924+30 is hence constrained to be $\delta < 0.15$ by fitting the shortest time to the previous comparable outburst that does not appreciably modify the remnant spectrum. The time-averaged feedback energy imparted by AGNs into their host galaxy environments can in this manner be quantified.

[15]  arXiv:1802.05823 [pdf, ps, other]
Title: Single Transits and Eclipses Observed by K2
Comments: 3 pages, 1 Table; accepted to RNAAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Photometric survey data from the Kepler mission have been used to discover and characterize thousands of transiting exoplanet and eclipsing binary (EB) systems. These discoveries have enabled empirical studies of occurrence rates which reveal that exoplanets are ubiquitous and found in a wide variety of system architectures and physical compositions. Because the detection strategy of these missions is most sensitive to short orbital periods, the vast majority of these objects reside within 1 AU of their host star. Although other detection techniques have successfully identified exoplanets at wider orbits beyond the snow lines of their respective host stars (e.g., radial velocity, microlensing, direct imaging), occurrence rates within this population remain poorly constrained. As such, identifying long period objects (LPOs) from archival Kepler and K2 data is valuable from both a statistical and theoretical standpoint, particularly for massive gas giants which are thought to heavily influence the formation and evolution dynamics of their respective systems. Here we present a catalog of 164 single transit and eclipse candidates detected during a comprehensive survey of all currently available K2 data.

[16]  arXiv:1802.05829 [pdf, ps, other]
Title: Magnetic Field Analysis of the Bow and Terminal Shock of the SS433 Jet
Comments: 22 pages, 10 figures, accepted for publication in PASJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We report a polarization analysis of the eastern region of W50, observed with the Australia Telescope Compact Array (ATCA) at 1.4 - 3.0 GHz. In order to study the physical structures in the region where the SS433 jet and W50 interact, we obtain an intrinsic magnetic field vector map of that region. We find that the orientation of the intrinsic magnetic field vectors are aligned along the total intensity structures, and that there are characteristic, separate structures related to the jet, the bow shock, and the terminal shock. The Faraday rotation measures (RMs), and the results of Faraday Tomography suggest that a high intensity, filamentary structure in the north-south direction of the eastern-edge region can be separated into at least two parts to the north and south. The results of Faraday Tomography also show that there are multiple components along the line of sight and/or within the beam area. In addition, we also analyze the X-ray ring-like structure observed with XMM-Newton. While the possibility still remains that this X-ray ring is real, it seems that the structure is not ring-like at radio wavelengths. Finally, we suggest that the structure is a part of the helical structure that coils the eastern ear of W50.

[17]  arXiv:1802.05836 [pdf, other]
Title: Impacts of nuclear-physics uncertainties in the s-process determined by Monte-Carlo variations
Comments: 6 pages, 4 figures, 2 tables, the Proceedings of "the 2017 Symposium on Nuclear Data"; a supplementary article of arXiv:1701.00489
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)

The s-process, a production mechanism based on slow-neutron capture during stellar evolution, is the origin of about half the elements heavier than iron. Abundance predictions for s-process nucleosynthesis depend strongly on the relevant neutron-capture and $\beta$-decay rates, as well as on the details of the stellar model being considered. Here, we have used a Monte-Carlo approach to evaluate the nuclear uncertainty in s-process nucleosynthesis. We considered the helium burning of massive stars for the weak s-process and low-mass asymptotic-giant-branch stars for the main s-process. Our calculations include a realistic and general prescription for the temperature dependent uncertainty for the reaction cross sections. We find that the adopted uncertainty for (${\rm n},\gamma$) rates, tens of per cent on average, effects the production of s-process nuclei along the line of $\beta$-stability, and that the uncertainties in $\beta$-decay from excited state contributions, has the strongest impact on branching points.

[18]  arXiv:1802.05837 [pdf, other]
Title: Sensitivity to neutron captures and beta-decays of the enhanced s-process in rotating massive stars at low metallicities
Comments: 3 pages, 3 figures, published in the Proceedings of "Nuclear Physics in Astrophysics Conference (NPA VII)"; see arXiv:1701.00489, for the completed results
Journal-ref: 2018 J. Phys.: Conf. Ser. 940 012051
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)

The s-process in massive stars, producing nuclei up to $A\approx 90$, has a different behaviour at low metallicity if stellar rotation is significant. This enhanced s-process is distinct from the s-process in massive stars around solar metallicity, and details of the nucleosynthesis are poorly known. We investigated nuclear physics uncertainties in the enhanced s-process in metal-poor stars within a Monte-Carlo framework. We applied temperature-dependent uncertainties of reaction rates, distinguishing contributions from the ground state and from excited states. We found that the final abundance of several isotopes shows uncertainties larger than a factor of 2, mostly due to the neutron capture uncertainties. A few nuclei around branching points are affected by uncertainties in the $\beta$-decay.

[19]  arXiv:1802.05840 [pdf, ps, other]
Title: Nonlinear spherical perturbations in Quintessence Models of Dark Energy
Comments: 23 pages, 15 figures. comments welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

Observations have confirmed the accelerated expansion of the universe. The accelerated expansion can be modelled by invoking a cosmological constant or a dynamical model of dark energy. A key difference between these models is that the equation of state parameter $w$ for dark energy differs from $-1$ in dynamical dark energy (DDE). Further, the equation of state parameter is not constant for a general DDE model. Such differences can be probed using the variation of scale factor with time by measuring distances. Another significant difference between the cosmological constant and DDE models is that the latter must cluster. Linear perturbation analysis indicates that perturbations in quintessence models of dark energy do not grow to have a significant amplitude at small length scales. In this paper we study the response of quintessence dark energy to non-linear perturbations in dark matter. We use a fully relativistic model for spherically symmetric perturbations. In this study we focus on thawing models. We find that in response to non-linear perturbations in dark matter, dark energy perturbations grow at a faster rate than expected in linear perturbation theory. We find that dark energy perturbation remains localised and does not diffuse out to larger scales. The dominant drivers of the evolution of dark energy perturbations are the local Hubble flow and a supression of gradients of the scalar field. We also find that the equation of state parameter $w$ changes in response to perturbations in dark matter such that it also becomes a function of position. The variation of $w$ in space is correlated with matter density perturbation. Variation of $w$ and perturbations in dark energy is more pronounced in response to large scale perturbations in matter while the dependence on the amplitude of matter perturbations is much weaker.

[20]  arXiv:1802.05850 [pdf, ps, other]
Title: Study of Magnetized accretion flow with cooling processes
Comments: 8 pages, 6 figures, published in a special issue of JApA
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We have studied shock in magnetized accretion flow/funnel flow in case of neutron star with bremsstrahlung cooling and cyclotron cooling. All accretion solutions terminate with a shock close to the neutron star surface, but at some region of the parameter space, it also harbours a second shock away from the star surface. We have found that cyclotron cooling is necessary for correct accretion solutions which match the surface boundary conditions.

[21]  arXiv:1802.05854 [pdf, other]
Title: The K2 M67 Study: A Curiously Young Star in an Eclipsing Binary in an Old Open Cluster
Comments: 33 pages, 11 figures, accepted to AJ, photometry files will be available with the electronic journal article
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present an analysis of a slightly eccentric ($e=0.05$), partially eclipsing long-period ($P = 69.73$ d) main sequence binary system (WOCS 12009, Sanders 1247) in the benchmark old open cluster M67. Using Kepler K2 and ground-based photometry along with a large set of new and reanalyzed spectra, we derived highly precise masses ($1.111\pm0.015$ and $0.748\pm0.005 M_\odot$) and radii ($1.071\pm0.008\pm0.003$ and $0.713\pm0.019\pm0.026 R_\odot$, with statistical and systematic error estimates) for the stars. The radius of the secondary star is in agreement with theory. The primary, however, is approximately $15\%$ smaller than reasonable isochrones for the cluster predict. Our best explanation is that the primary star was produced from the merger of two stars, as this can also account for the non-detection of photospheric lithium and its higher temperature relative to other cluster main sequence stars at the same $V$ magnitude. To understand the dynamical characteristics (low measured rotational line broadening of the primary star and the low eccentricity of the current binary orbit), we believe that the most probable (but not the only) explanation is the tidal evolution of a close binary within a primordial triple system (possibly after a period of Kozai-Lidov oscillations), leading to merger approximately 1Gyr ago. This star appears to be a future blue straggler that is being revealed as the cluster ages and the most massive main sequence stars die out.

[22]  arXiv:1802.05864 [pdf, ps, other]
Title: Search for Giant Pulses of radio pulsars at frequency 111 MHz with LPA radio telescope
Comments: 15 pages, 8 figures, Research in Astronomy and Astrophysics, in press
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We have used the unique low frequency sensitivity of the Large Phased Array radio telescope of Pushchino Radio Astronomy Observatory to collect dataset of the single pulse observations of second period pulsars of the Northern hemisphere. During observational sessions of 2011 - 2017 yrs. We have collected data on 71 pulsars at 111 MHz frequency using digital pulsar receiver. We have discovered Giant Radio Pulses (GRP) from pulsars B0301+09 and B1237+25, and confirmed early reported generation of anomalously strong (probable giant) pulses from B1133+16 on statistically significant dataset. Data for these pulsars and from B0950+08, B1112+50, early reported as pulsars generating GRPs were analyzed to evaluate their behavior on long time intervals. It was found that statistical criterion (power-law spectrum of GRPs distribution on energy and peak flux density) seems not to be strict for pulsars with the low magnetic field on light cylinder. Moreover, spectra of some of these pulsars demonstrate unstable behavior with the time and have complex multicomponent shape. In the dataset of B0950+08 we have detected strongest GRP from pulsars with the low magnetic field on light cylinder ever reported having the peak flux density as strong as 16.8 kJy.

[23]  arXiv:1802.05880 [pdf, other]
Title: Imprints of quasar duty cycle on the 21cm signal from the Epoch of Reionization
Authors: Florian Bolgar (1), Evan Eames (1), Clément Hottier (2), Benoit Semelin (1) ((1) LERMA, Observatoire de Paris, Sorbonne Université, PSL research university, (2) GEPI, Observatoire de Paris, Université PSL)
Comments: 14 pages, 10 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Quasars contribute to the 21-cm signal from the Epoch of Reionization (EoR) primarily through their ionizing UV and X-ray emission. However, their radio continuum and Lyman-band emission also regulates the 21-cm signal in their direct environment, potentially leaving the imprint of their duty cycle.
We develop a model for the radio and UV luminosity functions of quasars from the EoR, and constrain it using recent observations. Our model is consistent with the z~7.5 quasar from Banados et al 2017, and also predicts only a few quasars suitable for 21-cm forest observations (10mJy) in the sky. We exhibit a new effect on the 21-cm signal observed against the CMB: a radio-loud quasar can leave the imprint of its duty cycle on the 21-cm tomography. We apply this effect in a cosmological simulation and conclude that the effect of typical radio-loud quasars is most likely negligible in an SKA field of view. For a 1-10mJy quasar the effect is stronger though hardly observable at SKA resolution. Then we study the contribution of the lyman band Ly-alpha to Ly-beta) emission of quasars to the Wouthuisen-Field coupling. The collective effect of quasars on the 21-cm power spectrum is larger than the thermal noise at low k, though featureless. However, a distinctive pattern around the brightest quasars in an SKA field of view may be observable in the tomography, encoding the duration of their duty cycle. This pattern has a high signal-to-noise ratio for the brightest quasar in a typical SKA shallow survey.

[24]  arXiv:1802.05893 [pdf]
Title: A dual origin for water in carbonaceous asteroids revealed by CM chondrites
Comments: 20 pages, 3 figures, 2 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Carbonaceous asteroids represent the principal source of water in the inner Solar System and might correspond to the main contributors for the delivery of water to Earth. Hydrogen isotopes in water-bearing primitive meteorites, e.g. carbonaceous chondrites, constitute a unique tool for deciphering the sources of water reservoirs at the time of asteroid formation. However, fine-scale isotopic measurements are required to unravel the effects of parent body processes on the pre-accretion isotopic distributions. Here we report in situ micrometer-scale analyses of hydrogen isotopes in six CM-type carbonaceous chondrites revealing a dominant deuterium-poor water component ({\delta}D = -350 +/- 40 permil) mixed with deuterium-rich organic matter. We suggest that this D-poor water corresponds to a ubiquitous water reservoir in the inner protoplanetary disk. A deuterium-rich water signature has been preserved in the least altered part of the Paris chondrite ({\delta}DParis > -69 +/- 163 permil) in hydrated phases possibly present in the CM rock before alteration. The presence of the D-enriched water signature in Paris might indicate that transfers of ice from the outer to the inner Solar System have been significant within the first million years of the Solar System history.

[25]  arXiv:1802.05896 [pdf, other]
Title: Beryllium detection in the very fast nova ASASSN-16kt (V407 Lupi)
Comments: 11 pages, 8 figures, 4 tables. Accepted for publication in MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present high-resolution spectroscopic observations of the fast nova ASASSN-16kt (V407 Lup). A close inspection of spectra obtained at early stages has revealed the presence of low-ionization lines, and among the others we have identified the presence of the ionised $^7$Be doublet in a region relatively free from possible contaminants. After studying their intensities, we have inferred that ASASSN-16kt has produced (5.9 - 7.7)$ \times 10^{-9}$ M$_{\odot}$ of $^7$Be. The identification of bright Ne lines may suggest that the nova progenitor is a massive (1.2 M$_{\odot}$) oxygen-neon white dwarf. The high outburst frequency of oxygen-neon novae implies that they likely produce an amount of Be similar, if not larger, to that produced by carbon-oxygen novae, then confirming that classical novae are among the main factories of lithium in the Galaxy.

[26]  arXiv:1802.05916 [pdf, other]
Title: Early-type galaxy spin evolution in the Horizon-AGN simulation
Comments: Accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Using the Horizon-AGN simulation data, we study the relative role of mergers and environmental effects in shaping the spin of early-type galaxies (ETGs) after $z \simeq 1$. We follow the spin evolution of 10,037 color-selected ETGs more massive than 10$^{10} \rm \, M_{\odot}$ that are divided into four groups: cluster centrals (3%), cluster satellites (33%), group centrals (5%), and field ETGs (59%). We find a strong mass dependence of the slow rotator fraction, $f_{\rm SR}$, and the mean spin of massive ETGs. Although we do not find a clear environmental dependence of $f_{\rm SR}$, a weak trend is seen in the mean value of spin parameter driven by the satellite ETGs as they gradually lose their spin as their environment becomes denser. Galaxy mergers appear to be the main cause of total spin changes in 94% of central ETGs of halos with $M_{vir} > 10^{12.5}\rm M_{\odot}$, but only 22% of satellite and field ETGs. We find that non-merger induced tidal perturbations better correlate with the galaxy spin-down in satellite ETGs than mergers. Given that the majority of ETGs are not central in dense environments, we conclude that non-merger tidal perturbation effects played a key role in the spin evolution of ETGs observed in the local ($z < 1$) universe.

[27]  arXiv:1802.05940 [pdf, other]
Title: On Rotation Curve Analysis
Authors: Kevin Kadowaki
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

An analysis of analytical methods used for computing galactic masses on the basis of rotation curves (Saari 2015) is shown to be flawed.

[28]  arXiv:1802.05965 [pdf, ps, other]
Title: An extremely red and two other nearby L dwarf candidates previously overlooked in 2MASS, WISE, and other surveys
Comments: 2 pages, 1 table, accepted by RNAAS (abstract not included in original paper)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present three new nearby L dwarf candidates, found in a continued combined color/proper motion search using WISE, 2MASS, and other survey data, where we included extended WISE sources and looked closer to the Galactic plane region. Their spectral types and distances were estimated from photometric comparisons to well-known L dwarfs with trigonometric parallaxes. The first object, 2MASS J07555430-3259589, is an extremely red L7.5p dwarf candidate at a photometric distance of about 16 pc. Its position, proper motion and distance are consistent with membership in the Carina-Near young moving group. The second one, 2MASS J07414279-0506464, is resolved in Gaia DR1 as a close binary (separation 0.3 arcsec), and we classify it as a equal-mass binary candidate consisting of two L5 dwarfs at 19 pc. Our nearest new neighbor, 2MASS J19251275+0700362, is an L7 dwarf candidate at 10 pc.

[29]  arXiv:1802.05976 [pdf, ps, other]
Title: AKARI NEP-Deep: galaxy clustering through the AKARI IRC filters
Authors: A. Pollo, A. Solarz (and AKARI NEP Team)
Comments: To be published in AKARI 2017 Conference proceedings in JAXA Repository / AIREX (JAXA-SP series)
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We present a preliminary analysis of clustering of galaxies luminous in the near- and mid-infrared as seen by seven various ilters of the AKARI IRC instrument from 2 $\mu$m to 24 $\mu$m in the the AKARI NEP-Deep field. We compare populations of galaxies detected in different filters and their clustering properties. We conclude that different AKARI filters allow to trace different populations composed mainly of star-forming galaxies located in different environments. In particular, the mid-infrared filters at redshift z $\sim$ 0.8 and higher trace a population of strongly evolving galaxies located in massive haloes which might have ended as elliptical galaxies today.

[30]  arXiv:1802.06039 [pdf, other]
Title: Projected WIMP sensitivity of the LUX-ZEPLIN (LZ) dark matter experiment
Comments: 14 pages, 11 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)

LUX-ZEPLIN (LZ) is a next generation dark matter direct detection experiment that will operate 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. Using a two-phase xenon detector with an active mass of 7 tonnes, LZ will search primarily for low-energy interactions with Weakly Interacting Massive Particles (WIMPs), which are hypothesized to make up the dark matter in our galactic halo. In this paper, the projected WIMP sensitivity of LZ is presented based on the latest background estimates and simulations of the detector. For a 1000 live day run using a 5.6 tonne fiducial mass, LZ is projected to exclude at 90% confidence level spin-independent WIMP-nucleon cross sections above $1.6 \times 10^{-48}$ cm$^{2}$ for a 40 $\mathrm{GeV}/c^{2}$ mass WIMP. Additionally, a $5\sigma$ discovery potential is projected reaching cross sections below the existing and projected exclusion limits of similar experiments that are currently operating. For spin-dependent WIMP-neutron(-proton) scattering, a sensitivity of $2.7 \times 10^{-43}$ cm$^{2}$ ($8.1 \times 10^{-42}$ cm$^{2}$) for a 40 $\mathrm{GeV}/c^{2}$ mass WIMP is expected. With construction well underway, LZ is on track for underground installation at SURF in 2019 and will start collecting data in 2020.

[31]  arXiv:1802.06044 [pdf, other]
Title: No Giant Planet Pileup Near 1 AU
Comments: 3 pages, 1 figure, accepted to RNAAS Feb 8, 2018
Journal-ref: A. Wise and S. Dodson-Robinson 2018 Res. Notes AAS 2 29
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

A pileup near 1~AU in the semimajor axis distribution of giant exoplanets has been visually identified using log-spaced distribution plots. Here we propose that looking for features in a log-spaced semimajor axis distribution of giant planets is problematic. We use the Bayesian Blocks algorithm to analyze the linear-spaced semimajor axis distribution, and find that the apparent pileup is not significant.

[32]  arXiv:1802.06046 [pdf, other]
Title: Anisotropies in the stochastic gravitational wave background: formalism and the cosmic string case
Comments: 29 pages, 8 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)

We develop a powerful analytical formalism for calculating the energy density of the stochastic gravitational wave background, including a full description of its anisotropies. This is completely general, and can be applied to any astrophysical or cosmological source. As an example, we apply these tools to the case of a network of Nambu-Goto cosmic strings. We find that the anisotropies are relatively insensitive to the choice of model for the string network, but that they are very sensitive to the value of the string tension $G\mu$.

[33]  arXiv:1802.06056 [pdf, other]
Title: X-ray Reverberation Mapping and Dramatic Variability of Seyfert 1 Galaxy 1H 1934-063
Comments: 12 pages, 11 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

In addition to stochastic variability, a fraction of active galactic nuclei (AGN) are observed to exhibit dramatic variability in the X-ray band on timescales down to minutes. We introduce the case study of 1H 1934-063 (z = 0.0102), a Narrow-line Seyfert 1 (NLS1) among the brightest and most variable AGN ever observed with XMM-Newton. This work includes spectral and temporal analyses of a concurrent XMM-Newton and NuSTAR 2015 observation lasting 130 kiloseconds, during which the X-ray source exhibited a steep (factor of 6) plummet and subsequent full recovery of flux level. We rule out Compton-thin obscuration as the cause for this dramatic variability observed even at NuSTAR energies. In order to constrain coronal geometry, dynamics, and emission/absorption processes, we compare detailed spectral fitting with Fourier-based timing analysis. Similar to other well-studied, highly variable Seyfert 1s, this AGN is X-ray bright and displays strong reflection features. We find a narrower broad iron line component compared to most Seyfert 1s, and constrain black hole spin to be < 0.1, one of the lowest yet discovered for such systems. Combined spectral and timing results are consistent with a dramatic change in the continuum on timescales as short as a few kiloseconds dictating the nature of this variability. We also discover a Fe-K time lag and measure a delay of 20 seconds between relativistically-blurred reflection off the inner accretion flow (0.3-1 keV) and the hard X-ray continuum emission (1-4 keV).

[34]  arXiv:1802.06064 [pdf, ps, other]
Title: AD Leonis: Radial velocity signal of stellar rotation or spin-orbit resonance?
Comments: 19 pages (incl. example data tables), accepted for publication in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

AD Leonis is a nearby magnetically active M dwarf. We find Doppler variability with a period of 2.23 days as well as photometric signals: (1) a short period signal which is similar to the radial velocity signal albeit with considerable variability; and (2) a long term activity cycle of 4070$\pm$120 days. We examine the short-term photometric signal in the available ASAS and MOST photometry and find that the signal is not consistently present and varies considerably as a function of time. This signal undergoes a phase change of roughly 0.8 rad when considering the first and second halves of the MOST data set which are separated in median time by 3.38 days. In contrast, the Doppler signal is stable in the combined HARPS and HIRES radial velocities for over 4700 days and does not appear to vary in time in amplitude, phase, period or as a function of extracted wavelength. We consider a variety of star-spot scenarios and find it challenging to simultaneously explain the rapidly varying photometric signal and the stable radial velocity signal as being caused by starspots co-rotating on the stellar surface. This suggests that the origin of the Doppler periodicity might be the gravitational tug of a planet orbiting the star in spin-orbit resonance. For such a scenario and no spin-orbit misalignment, the measured $v \sin i$ indicates an inclination angle of 15.5$\pm$2.5 deg and a planetary companion mass of 0.237$\pm$0.047 M$_{\rm Jup}$.

[35]  arXiv:1802.06066 [pdf, other]
Title: Quantitative Constraints on the Reionization History from the IGM Damping Wing Signature in Two Quasars at z > 7
Comments: 18 pages, 13 figures. Submitted to ApJ
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

During reionization, neutral hydrogen in the intergalactic medium (IGM) imprints a damping wing absorption feature on the spectrum of high-redshift quasars. A detection of this signature provides compelling evidence for a significantly neutral Universe, and enables measurements of the hydrogen neutral fraction $x_{\rm HI}(z)$ at that epoch. Obtaining reliable quantitative constraints from this technique, however, is challenging due to stochasticity induced by the patchy inside-out topology of reionization, degeneracies with quasar lifetime, and the unknown unabsorbed quasar spectrum close to rest-frame Ly$\alpha$. We combine a large-volume semi-numerical simulation of reionization topology with 1D radiative transfer through high-resolution hydrodynamical simulations of the high-redshift Universe to construct models of quasar transmission spectra during reionization. Our state-of-the-art approach captures the distribution of damping wing strengths in biased quasar halos that should have reionized earlier, as well as the erosion of neutral gas in the quasar environment caused by its own ionizing radiation. Combining this detailed model with our new technique for predicting the quasar continuum and its associated uncertainty, we introduce a Bayesian statistical method to jointly constrain the neutral fraction of the Universe and the quasar lifetime from individual quasar spectra. We apply this methodology to the spectra of the two highest redshift quasars known, ULAS J1120+0641 and ULAS J1342+0928, and measured volume-averaged neutral fractions $\langle x_{\rm HI} \rangle(z=7.09)=0.48^{+0.26}_{-0.26}$ and $\langle x_{\rm HI} \rangle(z=7.54)=0.60^{+0.20}_{-0.23}$ (posterior medians and 68% credible intervals) when marginalized over quasar lifetimes of $10^3 \leq t_{\rm q} \leq 10^8$ years.

[36]  arXiv:1802.06069 [pdf, other]
Title: Inflation in a scale invariant universe
Comments: 9 pages, 2 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

A scale-invariant universe can have a period of accelerated expansion at early times: inflation. We use a frame-invariant approach to calculate inflationary observables in a scale invariant theory of gravity involving two scalar fields - the spectral indices, the tensor to scalar ratio, the level of isocurvature modes and non-Gaussianity. We show that scale symmetry leads to an exact cancellation of isocurvature modes and that, in the scale-symmetry broken phase, this theory is well described by a single scalar field theory. We find the predictions of this theory strongly compatible with current observations.

Cross-lists for Mon, 19 Feb 18

[37]  arXiv:1802.05289 (cross-list from physics.pop-ph) [pdf]
Title: Rejuvenating the Contract of Academia With Society
Authors: Abraham Loeb
Comments: 3 pages, Accepted for publication in Scientific American
Subjects: Popular Physics (physics.pop-ph); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Academia owes the public a fresh look at its education and research mission. First and foremost, researchers must communicate the results of their latest studies in a truthful and meaningful way. Second, the traditional boundaries among disciplines should be blurred since innovation often blossoms along these boundaries. Third, universities should develop courses which are relevant for the skills required in the job market today. Finally, professors should mentor the future leaders of science, technology, arts and humanities and not just replicate themselves.

[38]  arXiv:1802.05713 (cross-list from hep-ph) [pdf, other]
Title: A Simple No-Scale Model of Modulus Fixing and Inflation
Comments: 12 pages, 6 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)

We construct a no-scale model of inflation with a single modulus whose real and imaginary parts are both fixed by string-motivated corrections to the no-scale K{\" a}hler potential. Assuming an uplift of the minimum of the effective potential, the model yields a suitable number of e-folds of expansion and values of the tilt in the scalar cosmological density perturbations and of the ratio of tensor and scalar perturbations that are compatible with measurements of the cosmic microwave background radiation.

[39]  arXiv:1802.05718 (cross-list from gr-qc) [pdf, other]
Title: An Analytical Portrait of Binary Mergers in Hierarchical Triple Systems
Comments: 35 pages
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

With better statistics and precision, eccentricity could prove to be a useful tool for understanding the origin and environment of binary black holes. Hierarchical triples in particular, which are abundant in globular clusters and galactic nuclei, could generate observably large eccentricity at LIGO and future gravitational wave detectors. Measuring the eccentricity distribution accurately could help us probe the background and the formation of the mergers. In this paper we continue our previous investigation and improve our semi-analytical description of eccentricity distribution of mergers in galactic nuclei and other hierarchical triple systems. Our result, which further reduces the reliance on numerical simulations, could be useful for statistically distinguishing different formation channels of observed binary mergers.

[40]  arXiv:1802.05971 (cross-list from hep-ph) [pdf, other]
Title: Gamma rays from Dark Matter Annihilation in Three-loop Radiative Neutrino Mass Generation Models
Comments: 12 pages, 7 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE)

We present the Sommerfeld enhanced Dark Matter (DM) annihilation into gamma ray for a class of three-loop radiative neutrino mass models with large electroweak multiplets where the DM mass is in O(TeV) range. We show that in this model, the DM annihilation rate becomes more prominent for larger multiplets and it is already within the reach of currently operating Imaging Atmospheric Cherenkov telescopes (IACTs), High Energy Stereoscopic System (H.E.S.S.). Furthermore, Cherenkov Telescope Array (CTA), which will begin operating in 2030, will improve this sensitivity by a factor of $\mathcal{O}{(10)}$ and may exclude a large portion of parameter space of this radiative neutrino mass model with larger electroweak multiplet. This implies that the only viable option is the model with lowest electroweak multiplets i.e. singlets of $SU(2)_{L}$ where the DM annihilation rate is not Sommerfeld enhanced and hence it is not yet constrained by the indirect detection limits from H.E.S.S. or future CTA.

[41]  arXiv:1802.06000 (cross-list from physics.data-an) [pdf, other]
Title: On the Practical Applications of Information Field Dynamics
Authors: Martin Dupont
Subjects: Data Analysis, Statistics and Probability (physics.data-an); Instrumentation and Methods for Astrophysics (astro-ph.IM)

In this study we explore a new simulation scheme for partial differential equations known as Information Field Dynamics (IFD). Information field dynamics attempts to improve on existing simulation schemes by incorporating Bayesian field inference into the simulation scheme. The field inference is truly Bayesian and thus depends on a notion of prior belief. A number of results are presented, both theoretical and practical. Many small fixes and results on the general theory are presented, before exploring two general classes of simulation schemes that are possible in the IFD framework. For both, we present a set of theoretical results alongside the development of a prototype scheme. The first class of models corresponds roughly to traditional fixed-grid numerical PDE solvers. The prior Bayesian assumption in these models is that the fields are smooth, and their correlation structure does not vary between locations. For these reasons we call them translation-invariant schemes. We show the requirements for stability of these schemes, but most importantly we prove that these schemes indeed converge to the true behaviour of the field in the limit of high resolutions. Convergence had never been shown for any previous IFD scheme. We also find the error scaling of these codes and show that they implement something very analogous to a high-order finite-difference derivative approximation, which are the most elementary and well-studied numerical schemes. This is an important result, which proves the validity of the IFD approach. The second class of schemes, called the SPH-like schemes are similar to existing Smooth Particle Hydrodynamics codes, in which the simulation grid moves with the flow of the field being modelled.

Replacements for Mon, 19 Feb 18

[42]  arXiv:1703.05275 (replaced) [pdf, ps, other]
Title: Secluded and Putative Flipped Dark Matter and Stueckelberg Extensions of the Standard Model
Comments: 14 pages, no figures
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
[43]  arXiv:1707.03169 (replaced) [pdf, other]
Title: Morpho-z: improving photometric redshifts with galaxy morphology
Comments: 22 pages, 15 figures, accepted by MNRAS on 5 Dec 2017; redshift catalogues available at this ftp URL
Journal-ref: Soo J. Y. H. et al. (2018) MNRAS 475 3613
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)
[44]  arXiv:1707.03885 (replaced) [pdf, ps, other]
Title: On the phantom barrier crossing and the bounds on the speed of sound in non-minimal derivative coupling theories
Comments: 26 pages, 27 eps figures. Version accepted by the CQG journal
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[45]  arXiv:1707.07668 (replaced) [pdf, other]
Title: Unlocking Sensitivity for Visibility-based Estimators of the 21 cm Reionization Power Spectrum
Comments: 15 pages, 10 figures; Replaced with accepted ApJ version (some clarifying comments; no changes to results)
Journal-ref: ApJ 852, 110 (2018)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[46]  arXiv:1708.01360 (replaced) [pdf, ps, other]
[47]  arXiv:1708.06505 (replaced) [pdf, ps, other]
Title: Imaging Spectroscopy of Solar Radio Burst Fine Structures
Comments: 20 pages, 9 figures
Journal-ref: Nature Communications 8, Article number: 1515 (2017)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); Plasma Physics (physics.plasm-ph); Space Physics (physics.space-ph)
[48]  arXiv:1708.06560 (replaced) [pdf, other]
Title: A statistical analysis of two-dimensional patterns and its application to astrometry
Comments: 12 pages, 14 figures, 1 table. This version is accepted for publication in Astronomy & Astrophysics
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Phenomenology (hep-ph)
[49]  arXiv:1708.09425 (replaced) [pdf, ps, other]
Title: The effect of non-sphericity on mass and anisotropy measurements in dSph galaxies with Schwarzschild method
Comments: 14 pages, 12 figures, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[50]  arXiv:1709.05438 (replaced) [pdf, ps, other]
[51]  arXiv:1709.09695 (replaced) [pdf, ps, other]
Title: Higher-derivative operators and effective field theory for general scalar-tensor theories
Comments: 37+3 pages. v2: version published in JCAP
Journal-ref: JCAP 02 (2018) 031
Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
[52]  arXiv:1710.04729 (replaced) [pdf, other]
Title: Analysis of Dark Matter Axion Clumps with Spherical Symmetry
Comments: 32 pages, 8 figures. V2: Fixed figure 8 and equation 71. Added clarifications regarding spherical symmetry. Added references
Journal-ref: JCAP 01 (2018) 037
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Theory (hep-th)
[53]  arXiv:1711.01252 (replaced) [pdf, ps, other]
Title: MHD simulations of ram pressure stripping of a disk galaxy
Comments: 14 pages, 8 figures. Accepted for publication to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[54]  arXiv:1711.03916 (replaced) [pdf, ps, other]
Title: Non-axisymmetric aberration patterns from wide-field telescopes using spin-weighted Zernike Polynomials
Authors: Stephen M. Kent
Comments: 19 pages, 5 figures
Journal-ref: PASP, 130, 986 (2018)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
[55]  arXiv:1711.06266 (replaced) [pdf, ps, other]
Title: EUCLIA - Exploring the UV/optical continuum lag in active galactic nuclei. I. a model without light echoing
Authors: Zhen-Yi Cai (1), Jun-Xian Wang (1), Fei-Fan Zhu (1), Mou-Yuan Sun (1), Wei-Min Gu (2), Xin-Wu Cao (3), Feng Yuan (3) ((1) USTC, (2) XMU, (3) SHAO)
Comments: 18 pages, 8 figures. ApJ accepted. Further comments are very welcome!
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)
[56]  arXiv:1801.02821 (replaced) [pdf, other]
Title: Interstellar Interlopers: Number Density and Origins of 'Oumuamua-like Objects
Comments: 5 pages, 4 figures. Accepted for publication in ApJL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[57]  arXiv:1801.04004 (replaced) [pdf, other]
Title: Short arc orbit determination and imminent impactors in the Gaia era
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[58]  arXiv:1801.09801 (replaced) [pdf, other]
Title: A NIKA view of two star-forming infrared dark clouds: Dust emissivity variations and mass concentration
Comments: Abstract abridged. 18 pages, 16 figures, 2 tables. Accepted for publication in Astronomy & Astrophysics
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[59]  arXiv:1801.10178 (replaced) [pdf, other]
Title: Probing Cosmic Origins with CO and [CII] Emission Lines
Comments: We have corrected an error in PIXIE noise curve used in the previous version of the draft. This correction affected the constraints on local PNG from PIXIE. Version 2 of the draft is edited to reflect this change. In this version we also updated the reported Planck constraint to that from the combined temperature and polarization data
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
[60]  arXiv:1802.00693 (replaced) [pdf, other]
Title: A high-resolution study of levels in the astrophysically important nucleus $^{26}$Mg and resulting updated level assignments
Comments: 12 pages, 3 figures, 2 tables. Fixed missing reference and some index labelling in figures
Subjects: Nuclear Experiment (nucl-ex); Solar and Stellar Astrophysics (astro-ph.SR)
[61]  arXiv:1802.02255 (replaced) [pdf, ps, other]
Title: Model Selection Using Cosmic Chronometers with Gaussian Processes
Comments: 20 pages, 24 figures, 3 tables. Matches final published version in JCAP
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
[62]  arXiv:1802.05153 (replaced) [pdf, other]
Title: The Solar Wind Environment in Time
Comments: 21 pages, 11 figures, accepted for publication in ApJ, 8th February 2018
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[63]  arXiv:1802.05282 (replaced) [pdf, other]
Title: Further constraints on neutron star crustal properties in the low-mass X-ray binary 1RXS J180408.9$-$342058
Comments: Accepted for publication by MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[64]  arXiv:1802.05661 (replaced) [pdf, other]
Title: LISA sources in Milky-Way globular clusters
Comments: Submitted to PRL. Comments welcome
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)
[65]  arXiv:1802.05665 (replaced) [pdf, other]
Title: Solar-System Studies with Pulsar Timing Arrays
Authors: R. N. Caballero (for the EPTA and IPTA Collaborations)
Comments: 4 pages, 1 figure, accepted for publication in the proceedings of IAU Symposium 337 - Pulsar Astrophysics: The Next Fifty Years
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)
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