Search Publications
A Decade of Gamma-Ray Bursts Observed by Fermi-LAT: The Second GRB Catalog
Troja, E.; Caraveo, P. A.; Mirabal, N. +120 more
The Large Area Telescope (LAT) aboard the Fermi spacecraft routinely observes high-energy emission from gamma-ray bursts (GRBs). Here we present the second catalog of LAT-detected GRBs, covering the first 10 yr of operations, from 2008 to 2018 August 4. A total of 186 GRBs are found; of these, 91 show emission in the range 30-100 MeV (17 of which …
A year in the life of GW 170817: the rise and fall of a structured jet from a binary neutron star merger
Troja, E.; Piro, L.; van Eerten, H. +6 more
We present the results of our year-long afterglow monitoring of GW 170817, the first binary neutron star merger detected by Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo. New observations with the Australian Telescope Compact Array and the Chandra X-ray Telescope were used to constrain its late-time behavio…
Flare-productive active regions
Toriumi, Shin; Wang, Haimin
Strong solar flares and coronal mass ejections, here defined not only as the bursts of electromagnetic radiation but as the entire process in which magnetic energy is released through magnetic reconnection and plasma instability, emanate from active regions (ARs) in which high magnetic non-potentiality resides in a wide variety of forms. This revi…
The Spur and the Gap in GD-1: Dynamical Evidence for a Dark Substructure in the Milky Way Halo
Conroy, Charlie; Hogg, David W.; Price-Whelan, Adrian M. +1 more
We present a model for the interaction of the GD-1 stellar stream with a massive perturber that naturally explains many of the observed stream features, including a gap and an off-stream spur of stars. The model involves an impulse by a fast encounter, after which the stream grows a loop of stars at different orbital energies. At specific viewing …
The GALAH survey and Gaia DR2: dissecting the stellar disc's phase space by age, action, chemistry, and location
Lewis, Geraint F.; Ting, Yuan-Sen; Casey, Andrew R. +24 more
We use the second data releases of the European Space AgencyGaia astrometric survey and the high-resolution Galactic Archaeology with HERMES (GALAH) spectroscopic survey to analyse the structure of our Galaxy's disc components. With GALAH, we separate the α-rich and α-poor discs (with respect to Fe), which are superposed in both position and veloc…
The Milky Way has no in-situ halo other than the heated thick disc. Composition of the stellar halo and age-dating the last significant merger with Gaia DR2 and APOGEE
Katz, D.; Haywood, M.; Robichon, N. +5 more
Previous studies based on the analysis of Gaia DR2 data have revealed that accreted stars, possibly originating from a single progenitor satellite, are a significant component of the halo of our Galaxy, potentially constituting most of the halo stars at [Fe/H] < -1 within a few kpc from the Sun and beyond. In this paper, we couple astrometric d…
Cyclotron lines in highly magnetized neutron stars
Haberl, F.; Klochkov, D.; Santangelo, A. +10 more
Cyclotron lines, also called cyclotron resonant scattering features are spectral features, generally appearing in absorption, in the X-ray spectra of objects containing highly magnetized neutron stars, allowing the direct measurement of the magnetic field strength in these objects. Cyclotron features are thought to be due to resonant scattering of…
MOSFIRE Spectroscopy of Quiescent Galaxies at 1.5 < z < 2.5. II. Star Formation Histories and Galaxy Quenching
Ellis, Richard S.; Belli, Sirio; Newman, Andrew B.
We investigate the stellar populations for a sample of 24 quiescent galaxies at 1.5 < z < 2.5 using deep rest-frame optical spectra obtained with Keck MOSFIRE. By fitting templates simultaneously to the spectroscopic and photometric data and exploring a variety of star formation histories, we obtain robust measurements of median stellar ages…
An Analysis of the Shapes of Interstellar Extinction Curves. VII. Milky Way Spectrophotometric Optical-through-ultraviolet Extinction and Its R-dependence
Gordon, Karl D.; Fitzpatrick, E. L.; Clayton, Geoffrey C. +2 more
We produce a set of 72 NIR-through-UV extinction curves by combining new Hubble Space Telescope/STIS optical spectrophotometry with existing International Ultraviolet Explorer spectrophotometry (yielding gapless coverage from 1150 to 10000 Å) and NIR photometry. These curves are used to determine a new, internally consistent NIR-through-UV Milky W…
Deep learning of multi-element abundances from high-resolution spectroscopic data
Bovy, Jo; Leung, Henry W.
Deep learning with artificial neural networks is increasingly gaining attention because of its potential for data-driven astronomy. However, this methodology usually does not provide uncertainties and does not deal with incompleteness and noise in the training data. In this work, we design a neural network for high-resolution spectroscopic analysi…