Search Publications
Prevalence of SED Turndown among Classical Be Stars: Are All Be Stars Close Binaries?
Hallinan, G.; Klement, Robert; Carciofi, A. C. +16 more
Rapid rotation is a fundamental characteristic of classical Be stars and a crucial property allowing for the formation of their circumstellar disks. Past evolution in a mass and angular momentum transferring binary system offers a plausible solution to how Be stars attained their fast rotation. Although the subdwarf remnants of mass donors in such…
The mass-to-light ratios and the star formation histories of disc galaxies
Lelli, Federico; Schombert, James; McGaugh, Stacy
We combine new data from the main sequence (M* versus SFR) of star-forming galaxies and galaxy colours (from GALEX to Spitzer) with a flexible stellar population scheme to deduce the mass-to-light ratio (Υ*) of star-forming galaxies from the SPARC and S4G samples. We find that the main sequence for galaxies, partic…
Anisotropy of the Milky Way’s Stellar Halo Using K Giants from LAMOST and Gaia
Bird, Sarah A.; Yang, Chengqun; Liu, Chao +3 more
The anisotropy parameter β characterizes the extent to which orbits in stellar systems are predominantly radial or tangential and is likely to constrain, for the stellar halo of the Milky Way, scenarios for its formation and evolution. We have measured β as a function of Galactocentric radius from 5 to 100 kpc for 7664 metal-poor ([Fe/H] < -1.3…
Major Mergers Are Not the Dominant Trigger for High-accretion AGNs at z ∼ 2
Cohen, Seth; van der Wel, Arjen; Windhorst, Rogier A. +8 more
Research over the past decade has shown diminishing evidence for major galaxy mergers being a dominant mechanism for the growth of supermassive black holes (BHs) in galaxies and the triggering of optically or X-ray-selected active galactic nuclei (AGNs). For the first time we test whether such a connection exists at least in the most “plausible” p…
A Uniform Retrieval Analysis of Ultra-cool Dwarfs. III. Properties of Y Dwarfs
Line, Michael R.; Schneider, Adam C.; Patience, Jennifer +1 more
Ultra-cool brown dwarfs offer a unique window into understanding substellar atmospheric physics and chemistry. Their strong molecular absorption bands at infrared wavelengths, Jupiter-like radii, cool temperatures, and lack of complicating stellar irradiation make them ideal test beds for understanding Jovian-like atmospheres. Here, we report the …
Particle Acceleration at 5 au Associated with Turbulence and Small-scale Magnetic Flux Ropes
Chen, Y.; Zank, G. P.; Zhao, L. -L. +4 more
An observational analysis of an atypical energetic particle event near 5 au measured by the Ulysses spacecraft is presented. A previous study has attributed the unusual enhancement of energetic proton flux to the presence of small-scale dynamic magnetic islands or flux ropes. Here, we find that the generation of these magnetic islands may be relat…
GRB 161219B/SN 2016jca: a powerful stellar collapse
D'Avanzo, P.; Melandri, A.; Pian, E. +26 more
We report observations and analysis of the nearby gamma-ray burst GRB 161219B (redshift z = 0.1475) and the associated Type Ic supernova (SN) 2016jca. GRB 161219B had an isotropic gamma-ray energy of ∼1.6 × 1050 erg. Its afterglow is likely refreshed at an epoch preceding the first photometric points (0.6 d), which slows down the decay …
Rotation and pulsation in Ap stars: first light results from TESS sectors 1 and 2
Handler, G.; Niemczura, E.; Suárez, J. C. +36 more
We present the first results from the Transiting Exoplanet Survey Satellite (TESS) on the rotational and pulsational variability of magnetic chemically peculiar A-type stars. We analyse TESS 2-min cadence data from sectors 1 and 2 on a sample of 83 stars. Five new rapidly oscillating Ap (roAp) stars are announced. One of these pulsates with period…
ASASSN-18tb: a most unusual Type Ia supernova observed by TESS and SALT
Gromadzki, M.; Kochanek, C. S.; Stanek, K. Z. +16 more
We present photometric and spectroscopic observations of the unusual Type Ia supernova ASASSN-18tb, including a series of Southern African Large Telescope spectra obtained over the course of nearly six months and the first observations of a supernova by the Transiting Exoplanet Survey Satellite. We confirm a previous observation by Kollmeier et al…
Discovery of Strongly Inverted Metallicity Gradients in Dwarf Galaxies at z ∼ 2
Schmidt, Kasper B.; Treu, Tommaso; Daddi, Emanuele +12 more
We report the first measurements with sub-kiloparsec spatial resolution of strongly inverted gas-phase metallicity gradients in two dwarf galaxies at z ∼ 2. The galaxies have stellar masses ∼109 {M}⊙ , specific star formation rate ∼20 Gyr-1, and global metallicity 12+{log}({{O}}/{{H}})∼ 8.1 (1/4 solar), assuming t…