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Rapid Accretion State Transitions following the Tidal Disruption Event AT2018fyk
Wevers, T.; Uttley, P.; Miller-Jones, J. C. A. +7 more
Following a tidal disruption event (TDE), the accretion rate can evolve from quiescent to near-Eddington levels and back over timescales of months to years. This provides a unique opportunity to study the formation and evolution of the accretion flow around supermassive black holes (SMBHs). We present 2 yr of multiwavelength monitoring observation…
Dust temperature in ALMA [C II]-detected high-z galaxies
Zanella, A.; Ferrara, A.; Vallini, L. +4 more
At redshift z > 5, the far-infrared (FIR) continuum spectra of main-sequence galaxies are sparsely sampled, often with a single data point. The dust temperature Td,SED, thus has to be assumed in the FIR continuum fitting. This introduces large uncertainties regarding the derived dust mass (Md), FIR luminosity, and obscured…
Rapid Variability of Sgr A* across the Electromagnetic Spectrum
Morris, Mark R.; Smith, Howard A.; Fazio, G. G. +17 more
Sagittarius A* (Sgr A*) is the variable radio, near-infrared (NIR), and X-ray source associated with accretion onto the Galactic center black hole. We have analyzed a comprehensive submillimeter (including new observations simultaneous with NIR monitoring), NIR, and 2-8 keV data set. Submillimeter variations tend to lag those in the NIR by ~30 min…
Double-lined Spectroscopic Binaries in the APOGEE DR16 and DR17 Data
Bizyaev, Dmitry; Brownstein, Joel R.; Pan, Kaike +25 more
APOGEE spectra offer ≲1 km s-1 precision in the measurement of stellar radial velocities. This holds even when multiple stars are captured in the same spectrum, as happens most commonly with double-lined spectroscopic binaries (SB2s), although random line-of-sight alignments of unrelated stars can also occur. We develop a code that auto…
Bridging the Gap between Protoplanetary and Debris Disks: Separate Evolution of Millimeter and Micrometer-sized Dust
Matthews, Brenda C.; van der Marel, Nienke; Michel, Arnaud
The connection between the nature of a protoplanetary disk and that of a debris disk is not well understood. Dust evolution, planet formation, and disk dissipation likely play a role in the processes involved. We aim to reconcile both manifestations of dusty circumstellar disks through a study of optically thin Class III disks and how they correla…
The GALAH survey: a census of lithium-rich giant stars
Lewis, Geraint F.; Ting, Yuan-Sen; Buder, Sven +20 more
We investigate the properties of 1262 red giant stars with high photospheric abundances of lithium observed by the GALAH and K2-HERMES surveys, and discuss them in the context of proposed mechanisms for lithium enrichment and redepletion in giant stars. We confirm that Li-rich giants are rare, making up only 1.2 per cent of our giant star sample. …
Identifying resonances of the Galactic bar in Gaia DR2: I. Clues from action space
Fragkoudi, Francesca; White, Simon D. M.; Mackereth, J. Ted +2 more
Action space synthesizes the orbital information of stars and is well suited to analyse the rich kinematic substructure of the disc in the second Gaia data release's radial velocity sample. We revisit the strong perturbation induced in the Milky Way disc by an m = 2 bar, using test particle simulations and the actions (JR, Lz…
Detection of an Atmosphere on a Rocky Exoplanet
Sotin, Christophe; West, Robert; Zellem, Robert T. +7 more
We report the detection of an atmosphere on a rocky exoplanet, GJ 1132 b, which is similar to Earth in terms of size and density. The atmospheric transmission spectrum was detected using Hubble WFC3 measurements and shows spectral signatures of aerosol scattering, HCN, and CH4 in a low mean molecular weight atmosphere. We model the atmo…
What sustained multi-disciplinary research can achieve: The space weather modeling framework
Liemohn, Michael W.; van der Holst, Bart; Sokolov, Igor V. +15 more
Magnetohydrodynamics (MHD)-based global space weather models have mostly been developed and maintained at academic institutions. While the "free spirit" approach of academia enables the rapid emergence and testing of new ideas and methods, the lack of long-term stability and support makes this arrangement very challenging. This paper describes a s…
Speckle Observations of TESS Exoplanet Host Stars. II. Stellar Companions at 1-1000 au and Implications for Small Planet Detection
Lester, Kathryn V.; Howell, Steve B.; Hirsch, Lea A. +7 more
We present high-angular-resolution imaging observations of 517 host stars of TESS exoplanet candidates using the 'Alopeke and Zorro speckle cameras at Gemini North and South. The sample consists mainly of bright F, G, K stars at distances of less than 500 pc. Our speckle observations span angular resolutions of ~20 mas out to 1"2, yielding spatial…