Search Publications
Angular Momentum Variation of the Milky Way Thick Disk: The Dependence of Chemical Abundance and Evidence of the Inside-out Formation Scenario
Li, Lu; Hu, Guozhen; Shao, Zhengyi
We investigate the angular momentum of mono-abundance populations (MAPs) of the Milky Way thick disk by using a sample of 26,076 giant stars taken from APOGEE Data Release (DR) 17 and Gaia early DR3. The vertical and perpendicular angular momentum components, L Z and L P , of the MAPs in narrow bins have significant variat…
Searching for the Role of Mergers in Fast and Early SMBH Growth: Morphological Decomposition of Quasars and Their Hosts at z 4.8
Trakhtenbrot, Benny; Simmons, Brooke D.; Netzer, Hagai +4 more
We present rest-frame ultraviolet images of six luminous quasars at z ~ 4.8 obtained with the Hubble Space Telescope (HST). These quasars exhibit a wide range of star formation rates (SFRs) and lie in a wide range of environments. We carefully model and subtract the point-like quasar emission and investigate the morphology of the underlying host g…
Gaia17bpp: A Giant Star with the Deepest and Longest Known Dimming Event
Davenport, James R. A.; Bellm, Eric C.; Tzanidakis, Anastasios +1 more
We report the serendipitous discovery of Gaia17bpp/2MASS J19372316+1759029, a binary star with a deep single large-amplitude dimming event of ~4.5 mag that lasted over 6.5 yr. Using the optical-to-IR spectral energy distribution (SED), we constrain the primary star to be a cool giant M0III star with effective temperature T eff = 3850 K …
A Comparative Study of Ground-level Enhancement Events of Solar Energetic Particles
Vainio, Rami; Riihonen, Esa; Kocharov, Leon +2 more
Major solar eruptions can accelerate protons up to relativistic energies. Solar relativistic ions arriving at 1 au may cause a solar particle event detectable by the worldwide network of neutron monitors (NMs), a ground-level enhancement (GLE) event. Using the newly computed NM yield function, we have fitted the 15 historic GLEs. Moments of the fi…
Modeling the Chromosphere and Transition Region of Planet-hosting Star GJ 436
Peacock, Sarah; Barman, Travis; Hatzes, Artie P. +12 more
Ahead of upcoming space missions intending to conduct observations of low-mass stars in the ultraviolet (UV) spectral region it becomes imperative to simultaneously conduct atmospheric modeling from the UV to the visible (VIS) and near-infrared (NIR). Investigations on extended spectral regions will help to improve the overall understanding of the…
Massive Hypervelocity Runaway Stars in the Large Magellanic Cloud
Xu, Ye; Liu, Dejian; Hao, Chaojie +3 more
Since the hypervelocity stars were discovered in the Milky Way, various mechanisms have been proposed to explain these runaway stars. Up to now, however, the dominant ejected mechanism of hypervelocity stars is still unclear. As the largest and closest face-on satellite galaxy of the Milky Way, the Large Magellanic Cloud (LMC) serves as a good tar…
NuSTAR Hard X-Ray Monitoring of Gravitationally Lensed Quasar RX J1131-1231
Zoghbi, Abderahmen; Dai, Xinyu; Morgan, Christopher W. +2 more
The X-ray emission from active galactic nuclei is believed to come from a combination of inverse Compton scattering of photons from the accretion disk and reprocessing of the direct X-ray emission by reflection. We present hard (10-80 keV) and soft (0.5-8 keV) X-ray monitoring of a gravitationally lensed quasar RX J1131-1231 (hereafter RXJ1131) wi…
A Dynamically Distinct Stellar Population in the Leading Arm of the Sagittarius Stream
Beers, Timothy C.; Lee, Young Sun; Kang, Gwibong +1 more
We present a chemical and dynamical analysis of the leading arm (LA) and trailing arm (TA) of the Sagittarius (Sgr) stream, as well as for the Sgr dwarf galaxy core (SC), using red giant branch, main-sequence, and RR Lyrae stars from large spectroscopic survey data. The different chemical properties among the LA, TA, and SC generally agree with re…
Evolution of Magnetic Fields and Energy Release Processes during Homologous Eruptive Flares
Joshi, Bhuwan; Cho, Kyung-Suk; Sahu, Suraj +1 more
We explore the processes of the repetitive buildup and the explosive release of magnetic energy, together with the formation of magnetic flux ropes, which eventually resulted in three homologous eruptive flares of successively increasing intensities (i.e., M2.0, M2.6, and X1.0). The flares originated from NOAA active region 12017 between 2014 Marc…
A NICER Viewing Angle on the Accretion Stream of Vela X-1
Behar, Ehud; Rahin, Roi
Vela X-1 is the archetypal eclipsing high-mass X-ray binary, composed of a neutron star (NS) accreting the B-star wind. It was observed by nearly all X-ray observatories, often multiple times, featuring a rich spectrum of variable emission lines. However, the precise origin of these lines in the binary system remains uncertain. We perform a system…