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The Ultracool SpeXtroscopic Survey. I. Volume-limited Spectroscopic Sample and Luminosity Function of M7-L5 Ultracool Dwarfs
Burgasser, Adam J.; Faherty, Jacqueline K.; Gagné, Jonathan +9 more
We present a volume-limited, spectroscopically verified sample of M7-L5 ultracool dwarfs (UCDs) within 25 pc. The sample contains 410 sources, of which 93% have trigonometric distance measurements (80% from Gaia DR2) and 81% have low-resolution (R ∼ 120), near-infrared (NIR) spectroscopy. We also present an additional list of 60 sources that may b…
The Gaia ultracool dwarf sample - II. Structure at the end of the main sequence
Caballero, J. A.; Sarro, L. M.; Marocco, F. +4 more
We identify and investigate known late M, L, and T dwarfs in the Gaia second data release. This sample is being used as a training set in the Gaia data processing chain of the ultracool dwarfs work package. We find 695 objects in the optical spectral range M8-T6 with accurate Gaia coordinates, proper motions, and parallaxes which we combine with p…
Testing asteroseismology with Gaia DR2: hierarchical models of the Red Clump
Chaplin, William J.; Davies, Guy R.; García, Rafael A. +8 more
Asteroseismology provides fundamental stellar parameters independent of distance, but subject to systematics under calibration. Gaia DR2 has provided parallaxes for a billion stars, which are offset by a parallax zero-point (ϖzp). Red Clump (RC) stars have a narrow spread in luminosity, thus functioning as standard candles to calibrate …
On the dynamics of the Small Magellanic Cloud through high-resolution ASKAP H I observations
McClure-Griffiths, N. M.; Dickey, John M.; Staveley-Smith, L. +10 more
We use new high-resolution H I data from the Australian Square Kilometre Array Pathfinder to investigate the dynamics of the Small Magellanic Cloud (SMC). We model the H I gas component as a rotating disc of non-negligible angular size, moving into the plane of the sky, and undergoing nutation/precession motions. We derive a high-resolution (∼10 p…
Radial Variations in Grain Sizes and Dust Scale Heights in the Protoplanetary Disk around HD 163296 Revealed by ALMA Polarization Observations
Kataoka, Akimasa; Ohashi, Satoshi
The disk of HD 163296 shows ring and gap substructures in observations with the Atacama Large Millimeter/submillimeter Array. In addition, this is the only disk where the rings and gaps are spatially resolved in millimeter-wave polarization measurements. In this paper, we conduct radiative transfer modeling that includes self-scattering polarizati…
Revisiting the Spectral and Timing Properties of NGC 4151
Miller, J. M.; Zoghbi, A.; Cackett, E.
NGC 4151 is the brightest Seyfert 1 nucleus in X-rays. It was the first object to show short time delays in the Fe K band, which were attributed to relativistic reverberation, providing a new tool for probing regions at the black hole scale. Here we report the results of a large XMM-Newton campaign in 2015 to study these short delays further. Anal…
WOBBLE: A Data-driven Analysis Technique for Time-series Stellar Spectra
Hogg, David W.; Foreman-Mackey, Daniel; Bedell, Megan +2 more
In recent years, dedicated extreme precision radial velocity (RV) spectrographs have produced vast quantities of high-resolution, high-signal-to-noise (S/N) time-series spectra for bright stars. These data contain valuable information for the dual purposes of planet detection via the measured RVs and stellar characterization via the coadded spectr…
A massive white-dwarf merger product before final collapse
Langer, Norbert; Kniazev, Alexei Y.; Gvaramadze, Vasilii V. +4 more
Gravitational-wave emission can lead to the coalescence of close pairs of compact objects orbiting each other1,2. In the case of neutron stars, such mergers may yield masses above the Tolman-Oppenheimer-Volkoff limit (2 to 2.7 solar masses)3, leading to the formation of black holes4. For white dwarfs, the mass of t…
Self-lensing Discovery of a 0.2 M ⊙ White Dwarf in an Unusually Wide Orbit around a Sun-like Star
Bieryla, Allyson; Latham, David W.; Aoki, Wako +4 more
We report the discovery of the fifth self-lensing binary in which a low-mass white dwarf (WD) gravitationally magnifies its 15th magnitude G-star companion, KIC 8145411, during eclipses. The system was identified from a pair of such self-lensing events in the Kepler photometry, and was followed up with the Tillinghast Reflector Echelle Spectrograp…
A method for global inversion of multi-resolution solar data
de la Cruz Rodríguez, J.
Understanding the complex dynamics and structure of the upper solar atmosphere strongly benefits from the use of a combination of several diagnostics. Frequently, such diverse diagnostics can only be obtained from telescopes and/or instrumentation operating at widely different spatial resolution. To optimize the utilization of such data, we propos…