June 2019

Morpheus: A Deep Learning Framework For Pixel-Level Analysis of Astronomical Image Data. (arXiv:1906.11248v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Hausen_R/0/1/0/all/0/1">Ryan Hausen</a> (UCSC), <a href="http://arxiv.org/find/astro-ph/1/au:+Robertson_B/0/1/0/all/0/1">Brant Robertson</a> (UCSC, IAS) We present Morpheus, a new model for generating pixel level morphological classifications of astronomical sources. Morpheus leverages advances in deep learning to perform source detection, source segmentation, and morphological classification pixel-by-pixel via a semantic segmentation algorithm adopted from the field of computer vision. By utilizing morphological information about the flux of real astronomical sources during object detection, Morpheus shows resiliency to false positive identifications of sources. We evaluate Morpheus by performing source detection, source segmentation, morphological classification on the Hubble Space TelescopeRead More →

Convective Overshoot and Macroscopic Diffusion in Pure-Hydrogen Atmosphere White Dwarfs. (arXiv:1906.11252v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Cunningham_T/0/1/0/all/0/1">Tim Cunningham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tremblay_P/0/1/0/all/0/1">Pier-Emmanuel Tremblay</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Freytag_B/0/1/0/all/0/1">Bernd Freytag</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ludwig_H/0/1/0/all/0/1">Hans-G&#xfc;nther Ludwig</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koester_D/0/1/0/all/0/1">Detlev Koester</a> We present a theoretical description of macroscopic diffusion caused by convective overshoot in pure-hydrogen DA white dwarfs using three-dimensional (3D), closed-bottom, radiation hydrodynamics CO$^5$BOLD simulations. We rely on a new grid of deep 3D white dwarf models in the temperature range 11400 K $leq T_{mathrm{eff}} leq$ 18000 K where tracer particles and a tracer density are used to derive macroscopic diffusion coefficients driven by convective overshoot. These diffusion coefficients are compared to microscopic diffusion coefficients from one-dimensional structures.Read More →

Late time transitions in the quintessence field and the $H_0$ tension. (arXiv:1906.11255v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Valentino_E/0/1/0/all/0/1">Eleonora Di Valentino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ferreira_R/0/1/0/all/0/1">Ricardo Z. Ferreira</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Visinelli_L/0/1/0/all/0/1">Luca Visinelli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Danielsson_U/0/1/0/all/0/1">Ulf Danielsson</a> We consider a quintessence field which transitions from a matter-like to a cosmological constant behavior between recombination and the present time. We aim at easing the tension in the measurement of the present Hubble rate, and we assess the $Lambda$CDM model properly enlarged to include our quintessence field against cosmological observations. The model does not address the scope we proposed. This result allows us to exclude a class of quintessential models as a solution to the tension inRead More →

An empirically-derived formula for the shape of planet-induced gaps in protoplanetary disks. (arXiv:1906.11256v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Duffell_P/0/1/0/all/0/1">Paul C. Duffell</a> This study uses numerical hydrodynamics calculations and a novel method for densely sampling parameter space to measure the precise shape of a gap opened by a planet in a gaseous disk, as a function of planet-to-star mass ratio, disk Mach number, and disk viscosity. Formulas for gap depth and width are determined, which are combined to form a complete formula for surface density as a function of radius in the disk. This new analytical formula is compared with numerically-derived gaps opened by planets ranging from very lowRead More →

Dragonfly imaging of the galaxy NGC5907: a revised view of the iconic stellar stream. (arXiv:1906.11260v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Dokkum_P/0/1/0/all/0/1">Pieter van Dokkum</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gilhuly_C/0/1/0/all/0/1">Colleen Gilhuly</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonaca_A/0/1/0/all/0/1">Ana Bonaca</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Merritt_A/0/1/0/all/0/1">Allison Merritt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Danieli_S/0/1/0/all/0/1">Shany Danieli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lokhorst_D/0/1/0/all/0/1">Deborah Lokhorst</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Abraham_R/0/1/0/all/0/1">Roberto Abraham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Conroy_C/0/1/0/all/0/1">Charlie Conroy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Greco_J/0/1/0/all/0/1">Johnny P. Greco</a> In 2008 it was reported that the stellar stream of the edge-on spiral NGC5907 loops twice around the galaxy, enveloping it in a giant corkscrew-like structure. Here we present imaging of this iconic object with the Dragonfly Telephoto Array, reaching $1sigma$ surface brightness levels of $mu_gapprox 30.5$ mag/arcsec$^2$ on arcminute scales. We find that the stream has a qualitatively differentRead More →

Self-consistent proto-globular cluster formation in cosmological simulations of high-redshift galaxies. (arXiv:1906.11261v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Ma_X/0/1/0/all/0/1">Xiangcheng Ma</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Grudic_M/0/1/0/all/0/1">Michael Y. Grudi&#x107;</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Quataert_E/0/1/0/all/0/1">Eliot Quataert</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Hopkins_P/0/1/0/all/0/1">Philip F. Hopkins</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Faucher_Giguere_C/0/1/0/all/0/1">Claude-Andr&#xe9; Faucher-Gigu&#xe8;re</a> (3), <a href="http://arxiv.org/find/astro-ph/1/au:+Boylan_Kolchin_M/0/1/0/all/0/1">Michael Boylan-Kolchin</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Wetzel_A/0/1/0/all/0/1">Andrew Wetzel</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_J/0/1/0/all/0/1">Ji-hoon Kim</a> (6), <a href="http://arxiv.org/find/astro-ph/1/au:+Murray_N/0/1/0/all/0/1">Norman Murray</a> (7), <a href="http://arxiv.org/find/astro-ph/1/au:+Keres_D/0/1/0/all/0/1">Du&#x161;an Kere&#x161;</a> (8) ((1) Berkeley, (2) Caltech, (3) Northwestern, (4) UT Austin, (5) UC Davis, (6) SNU, (7) CITA, (8) UCSD) We report the formation of bound star clusters in a sample of high-resolution cosmological zoom-in simulations of z>5 galaxies from the FIRE project. We find that bound clusters preferentially form in high-pressure cloudsRead More →

The Random Transiter — EPIC 249706694/HD 139139. (arXiv:1906.11268v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Rappaport_S/0/1/0/all/0/1">S. Rappaport</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vanderburg_A/0/1/0/all/0/1">A. Vanderburg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kristiansen_M/0/1/0/all/0/1">M.H. Kristiansen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Omohundro_M/0/1/0/all/0/1">M.R. Omohundro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schwengeler_H/0/1/0/all/0/1">H.M. Schwengeler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Terentev_I/0/1/0/all/0/1">I.A. Terentev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dai_F/0/1/0/all/0/1">F. Dai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Masuda_K/0/1/0/all/0/1">K. Masuda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jacobs_T/0/1/0/all/0/1">T.L. Jacobs</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+LaCourse_D/0/1/0/all/0/1">D. LaCourse</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Latham_D/0/1/0/all/0/1">D.W. Latham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bieryla_A/0/1/0/all/0/1">A. Bieryla</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hedges_C/0/1/0/all/0/1">C.L. Hedges</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dittmann_J/0/1/0/all/0/1">J. Dittmann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barentsen_G/0/1/0/all/0/1">G. Barentsen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cochran_W/0/1/0/all/0/1">W. Cochran</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Endl_M/0/1/0/all/0/1">M. Endl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jenkins_J/0/1/0/all/0/1">J.M. Jenkins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mann_A/0/1/0/all/0/1">A. Mann</a> We have identified a star, EPIC 249706694 (HD 139139), that was observed during K2 Campaign 15 with the Kepler extended mission that appears to exhibit 28 transit-like events over the course of the 87-day observation. The unusual aspect ofRead More →

Cosmological simulations of massive black hole seeds: predictions for next generation electromagnetic and gravitational wave observations. (arXiv:1906.11271v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+DeGraf_C/0/1/0/all/0/1">Colin DeGraf</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sijacki_D/0/1/0/all/0/1">Debora Sijacki</a> We study how statistical properties of supermassive black holes depend on the frequency and conditions for massive seed formation in cosmological simulations of structure formation. We develop a novel method to re-calculate detailed growth histories and merger trees of black holes within the framework of the Illustris simulation for several seed formation models, including a physically motivated model where black hole seeds only form in progenitor galaxies that conform to the conditions for direct collapse black hole formation. While all seedRead More →

Do Reverberation Mapping Analyses Provide an Accurate Picture of the Broad Line Region?. (arXiv:1906.11272v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Mangham_S/0/1/0/all/0/1">S. W. Mangham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Knigge_C/0/1/0/all/0/1">C. Knigge</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Williams_P/0/1/0/all/0/1">P. Williams</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Horne_K/0/1/0/all/0/1">Keith Horne</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pancoast_A/0/1/0/all/0/1">A. Pancoast</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Matthews_J/0/1/0/all/0/1">J. H. Matthews</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Long_K/0/1/0/all/0/1">K. S. Long</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sim_S/0/1/0/all/0/1">S. A. Sim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Higginbottom_N/0/1/0/all/0/1">N. Higginbottom</a> Reverberation mapping (RM) is a powerful approach for determining the nature of the broad-line region (BLR) in active galactic nuclei. However, inferring physical BLR properties from an observed spectroscopic time series is a difficult inverse problem. Here, we present a blind test of two widely used RM methods: MEMEcho (developed by Horne) and CARAMEL (developed by Pancoast and collaborators).Read More →

Strong New Limits on Light Dark Matter from Neutrino Experiments. (arXiv:1906.11283v1 [hep-ph]) <a href="http://arxiv.org/find/hep-ph/1/au:+Cappiello_C/0/1/0/all/0/1">Christopher V. Cappiello</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Beacom_J/0/1/0/all/0/1">John F. Beacom</a> The non-detection of GeV-scale WIMPs has led to increased interest in more general candidates, including sub-GeV dark matter. Direct detection experiments, despite their high sensitivity to WIMPs, are largely blind to sub-GeV dark matter. Recent work has shown that cosmic-ray elastic scattering with sub-GeV dark matter would both alter the observed cosmic ray spectra and produce a flux of relativistic dark matter, which would be detectable with traditional dark matter experiments as well as larger, higher-threshold detectors for neutrinos. Using data, detectors, and analysis techniquesRead More →

Cyanopolyyne Chemistry around Massive Young Stellar Objects. (arXiv:1906.11296v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Taniguchi_K/0/1/0/all/0/1">Kotomi Taniguchi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Herbst_E/0/1/0/all/0/1">Eric Herbst</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Caselli_P/0/1/0/all/0/1">Paola Caselli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Paulive_A/0/1/0/all/0/1">Alec Paulive</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Maffucci_D/0/1/0/all/0/1">Dominique M. Maffucci</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Saito_M/0/1/0/all/0/1">Masao Saito</a> Recent radio astronomical observations have revealed that HC$_{5}$N, the second shortest cyanopolyyne (HC$_{2n+1}$N), is abundant around some massive young stellar objects (MYSOs), which is not predicted by classical carbon-chain chemistry. For example, the observed HC$_{5}$N abundance toward the G28.28$-$0.36 MYSO is higher than that in L1527, which is one of the warm carbon chain chemistry (WCCC) sources, by more than one order of magnitude (Taniguchi et al., 2017). In this paper, we present chemical simulations of hot-coreRead More →

Can Neutron-Star Mergers Explain the r-process Enrichment in Globular Clusters?. (arXiv:1906.11299v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Zevin_M/0/1/0/all/0/1">Michael Zevin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kremer_K/0/1/0/all/0/1">Kyle Kremer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Siegel_D/0/1/0/all/0/1">Daniel M. Siegel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Coughlin_S/0/1/0/all/0/1">Scott Coughlin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tsang_B/0/1/0/all/0/1">Benny T.-H. Tsang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berry_C/0/1/0/all/0/1">Christopher P. L. Berry</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kalogera_V/0/1/0/all/0/1">Vicky Kalogera</a> Star-to-star dispersion of r-process elements has been observed in a significant number of old, metal-poor globular clusters. We investigate early-time neutron-star mergers as the mechanism for this enrichment. We show that neutron-star mergers cannot be induced through dynamical interactions early in the history of the cluster, even when the most liberal assumptions about neutron-star segregation are assumed. Therefore, if neutron-star mergers are the primary mechanism for r-process dispersionRead More →

CHIME/FRB Detection of the Original Repeating Fast Radio Burst Source FRB 121102. (arXiv:1906.11305v1 [astro-ph.HE]) <a href="http://arxiv.org/find/astro-ph/1/au:+Josephy_A/0/1/0/all/0/1">A. Josephy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chawla_P/0/1/0/all/0/1">P. Chawla</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fonseca_E/0/1/0/all/0/1">E. Fonseca</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ng_C/0/1/0/all/0/1">C. Ng</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Patel_C/0/1/0/all/0/1">C. Patel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pleunis_Z/0/1/0/all/0/1">Z. Pleunis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Scholz_P/0/1/0/all/0/1">P. Scholz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Andersen_B/0/1/0/all/0/1">B. C. Andersen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bandura_K/0/1/0/all/0/1">K. Bandura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bhardwaj_M/0/1/0/all/0/1">M. Bhardwaj</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Boyce_M/0/1/0/all/0/1">M. M. Boyce</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Boyle_P/0/1/0/all/0/1">P. J. Boyle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brar_C/0/1/0/all/0/1">C. Brar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cubranic_D/0/1/0/all/0/1">D. Cubranic</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dobbs_M/0/1/0/all/0/1">M. Dobbs</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gaensler_B/0/1/0/all/0/1">B. M. Gaensler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gill_A/0/1/0/all/0/1">A. Gill</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Giri_U/0/1/0/all/0/1">U. Giri</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Good_D/0/1/0/all/0/1">D. C. Good</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Halpern_M/0/1/0/all/0/1">M. Halpern</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hinshaw_G/0/1/0/all/0/1">G. Hinshaw</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kaspi_V/0/1/0/all/0/1">V. M. Kaspi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Landecker_T/0/1/0/all/0/1">T. L. Landecker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lang_D/0/1/0/all/0/1">D. A. Lang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lin_H/0/1/0/all/0/1">H.-H. Lin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Masui_K/0/1/0/all/0/1">K. W. Masui</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mckinven_R/0/1/0/all/0/1">R. Mckinven</a>, <aRead More →

Shiva: the dust destruction model. (arXiv:1906.11308v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Murga_M/0/1/0/all/0/1">M. S. Murga</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wiebe_D/0/1/0/all/0/1">D. S. Wiebe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sivkova_E/0/1/0/all/0/1">E. E. Sivkova</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Akimkin_V/0/1/0/all/0/1">V. V. Akimkin</a> We present a numerical tool Shiva designed to simulate the dust destruction in warm neutral, warm ionized, and hot ionized media under the influence of photo-processing, sputtering, and shattering. The tool is designed primarily to study the evolution of hydrogenated amorphous carbons (HACs), but options to simulate polycyclic aromatic hydrocarbons (PAHs), silicate and graphite grains are also implemented. HAC grain photo-processing includes both dehydrogenation and carbon atom loss. Dehydrogenation leads to material transformation from aliphatic to aromatic structure. Simultaneously, some other physicalRead More →

Exact solutions for compact stars with CFL quark matter. (arXiv:1906.11311v1 [gr-qc]) <a href="http://arxiv.org/find/gr-qc/1/au:+Rocha_L/0/1/0/all/0/1">L. S. Rocha</a> (IAG – USP), <a href="http://arxiv.org/find/gr-qc/1/au:+Bernardo_A/0/1/0/all/0/1">A. Bernardo</a> (IAG – USP), <a href="http://arxiv.org/find/gr-qc/1/au:+Avellar_M/0/1/0/all/0/1">M. G. B. de Avellar</a> (UNIFESP – DIADEMA, ITA), <a href="http://arxiv.org/find/gr-qc/1/au:+Horvath_J/0/1/0/all/0/1">J. E. Horvath</a> (IAG – USP) The search for the true ground state of the dense matter remains open since Bomer, Terasawa and other raised the possibility of stable quarks, boosted by Witten’s textit{strange matter} hypothesis in 1984. Within this proposal, the strange matter is assumed to be composed of $strange$ quarks in addition to the usual $up$s and $down$s, having an energy per baryon lower than the strangeless counterpart,Read More →

Identification and correction of Sagnac frequency variations: an implementation for the GINGERINO data analysis. (arXiv:1906.11338v1 [physics.ins-det]) <a href="http://arxiv.org/find/physics/1/au:+Virgilio_A/0/1/0/all/0/1">Angela D.V. Di Virgilio</a>, <a href="http://arxiv.org/find/physics/1/au:+Giacomelli_U/0/1/0/all/0/1">Umberto Giacomelli</a>, <a href="http://arxiv.org/find/physics/1/au:+Beverini_N/0/1/0/all/0/1">Nicol&#xf2; Beverini</a>, <a href="http://arxiv.org/find/physics/1/au:+Carelli_G/0/1/0/all/0/1">Giorgio Carelli</a>, <a href="http://arxiv.org/find/physics/1/au:+Ciampini_D/0/1/0/all/0/1">Donatella Ciampini</a>, <a href="http://arxiv.org/find/physics/1/au:+Fuso_F/0/1/0/all/0/1">Francesco Fuso</a>, <a href="http://arxiv.org/find/physics/1/au:+Maccioni_E/0/1/0/all/0/1">Enrico Maccioni</a>, <a href="http://arxiv.org/find/physics/1/au:+Ortolan_A/0/1/0/all/0/1">Antonello Ortolan</a> Ring laser gyroscopes are top sensitivity inertial sensors used in the measurement of angular rotation rates. It is well known that the response of such remarkable instruments can in principle access the very low frequency band, but the occurrence of nonlinear effects in the laser dynamics imposes severe limitations in terms of sensitivity and stability. We report here general relationships aimed at evaluatingRead More →

The diversity of AGN variability: Some highlights and challenges. (arXiv:1906.11339v1 [astro-ph.GA]) <a href="http://arxiv.org/find/astro-ph/1/au:+Gopal-Krishna/0/1/0/all/0/1">Gopal-Krishna</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Britzen_S/0/1/0/all/0/1">Silke Britzen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wiita_P/0/1/0/all/0/1">Paul Wiita</a> This article focuses on certain variability and emission characteristics of Active Galactic Nuclei (AGN), especially their radio-loud subset consisting of quasars, BL Lacs and $gamma$-ray detected narrow-line Seyfert 1 galaxies, all of which exhibit relativistically beamed jets of nonthermal radiation. Several striking trends and correlations, including some that have received scant attention, drawn from the available comparatively recent literature are highlighted. These can provide very useful inputs to models of AGN and be probed at a deeper level using the optical telescopes recently set up atRead More →

Trans-Neptunian Binaries as Evidence for Planetesimal Formation by the Streaming Instability. (arXiv:1906.11344v1 [astro-ph.EP]) <a href="http://arxiv.org/find/astro-ph/1/au:+Nesvorny_D/0/1/0/all/0/1">David Nesvorny</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_R/0/1/0/all/0/1">Rixin Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Youdin_A/0/1/0/all/0/1">Andrew N. Youdin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Simon_J/0/1/0/all/0/1">Jacob B. Simon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Grundy_W/0/1/0/all/0/1">William M. Grundy</a> A critical step toward the emergence of planets in a protoplanetary disk consists in accretion of planetesimals, bodies 1-1000 km in size, from smaller disk constituents. This process is poorly understood partly because we lack good observational constraints on the complex physical processes that contribute to planetesimal formation. In the outer solar system, the best place to look for clues is the Kuiper belt, where icy planetesimals survived to this day. Here we reportRead More →