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Searches after Gravitational Waves Using ARizona Observatories (SAGUARO): System Overview and First Results from Advanced LIGO/Virgo’s Third Observing Run
Gabor, P.; Palazzi, E.; Smith, N. +54 more
We present Searches After Gravitational-waves Using ARizona Observatories (SAGUARO), a comprehensive effort dedicated to the discovery and characterization of optical counterparts to gravitational-wave (GW) events. SAGUARO utilizes ground-based facilities ranging from 1.5 to 10 m in diameter, located primarily in the Northern Hemisphere. We provid…
NuSTAR Observations of the Accreting Atolls GX 3+1, 4U 1702-429, 4U 0614+091, and 4U 1746-371
Harrison, F. A.; Degenaar, N.; Miller, J. M. +7 more
Atoll sources are accreting neutron star (NS) low-mass X-ray binaries. We present a spectral analysis of four persistent atoll sources (GX 3+1, 4U 1702-429, 4U 0614+091, and 4U 1746-371) observed for ∼20 ks each with NuSTAR to determine the extent of the inner accretion disk. These sources range from an apparent luminosity of 0.006-0.11 of the Edd…
Flame-like Ellerman Bombs and Their Connection to Solar Ultraviolet Bursts
Chen, Yajie; Cao, Wenda; Wang, Haimin +6 more
Ellerman bombs (EBs) are small-scale intense brightenings in Hα wing images, which are generally believed to be signatures of magnetic reconnection around the temperature minimum region of the solar atmosphere. They have a flame-like morphology when observed near the solar limb. Recent observations from the Interface Region Imaging Spectrograph (I…
Modelling the spectral energy distribution of super-Eddington quasars
Done, Chris; Kubota, Aya
We develop a broad-band spectral model, AGNSLIM, to describe super-Eddington black hole accretion disc spectra. This is based on the slim disc emissivity, where radial advection keeps the surface luminosity at the local Eddington limit, resulting in L(r) ∝ r-2 rather than the r-3 expected from the Novikov-Thorne (standard, su…
Arecibo radar observations of near-Earth asteroid (3200) Phaethon during the 2017 apparition
Bhiravarasu, Sriram S.; Benner, Lance A. M.; Giorgini, Jon D. +8 more
We report Arecibo S-band (2380 MHz; 12.6 cm) radar observations of near-Earth asteroid (3200) Phaethon during the December 2017 apparition when Phaethon passed within 0.07 au of Earth. Radar images with a resolution of 75 m per pixel reveal a roughly spheroidal shape more than 6 km in diameter at the equator with several discernible surface featur…
Jupiter's ammonia distribution derived from VLA maps at 3-37 GHz
de Pater, Imke; Sault, R. J.; Wong, Michael H. +3 more
We observed Jupiter four times over a full rotation (10 h) with the upgraded Karl G. Jansky Very Large Array (VLA) between December 2013 and December 2014. Preliminary results at 4-17 GHz were presented in de Pater et al. (2016); in the present paper we present the full data set at frequencies between 3 and 37 GHz. Major findings are:
i) The …Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2. II. Resolved common proper motion pairs
Mérand, Antoine; Evans, Nancy Remage; Gieren, Wolfgang +6 more
Context. The multiplicity of classical Cepheids (CCs) and RR Lyrae stars (RRLs) is still imperfectly known, particularly for RRLs.
Aims: In order to complement the close-in short orbital period systems presented in Paper I, our aim is to detect the wide, spatially resolved companions of the targets of our reference samples of Galactic CCs and…
The age of the Galactic stellar halo from Gaia white dwarfs
Hambly, N. C.; Rowell, N.; Bergeron, P. +3 more
We use 156 044 white dwarf candidates with ≥5σ significant parallax measurements from the Gaia mission to measure the velocity dispersion of the Galactic disc; (σU, σV, σW) = (30.8, 23.9, 20.0) km s-1. We identify 142 objects that are inconsistent with disc membership at the >5σ level. This is the lar…
The role of molecular filaments in the origin of the prestellar core mass function and stellar initial mass function
André, Ph.; Arzoumanian, D.; Könyves, V. +2 more
Context. The origin of the stellar initial mass function (IMF) is one of the most debated issues in astrophysics.
Aims: Here we explore the possible link between the quasi-universal filamentary structure of star-forming molecular clouds and the origin of the IMF.
Methods: Based on our recent comprehensive study of filament properties fro…
The Evolution of the He II-ionizing Background at Redshifts 2.3 < z < 3.8 Inferred from a Statistical Sample of 24 HST/COS He II Lyα Absorption Spectra
Hennawi, Joseph F.; Worseck, Gábor; Prochaska, J. Xavier +1 more
We present measurements of the large-scale (≈40 comoving Mpc) effective optical depth of He II Lyα absorption, {τ }eff}, at 2.54 < z < 3.86 toward 16 He II-transparent quasars observed with the Cosmic Origins Spectrograph on the Hubble Space Telescope, to characterize the ionization state of helium in the intergalactic medium (IGM…