Search Publications
Pre-main-sequence Brackett Emitters in the APOGEE DR17 Catalog: Line Strengths and Physical Properties of Accretion Columns
Stassun, Keivan G.; Kounkel, Marina; Stringfellow, Guy S. +21 more
Very young (t ≲ 10 Myr) stars possess strong magnetic fields that channel ionized gas from the interiors of their circumstellar disks to the surface of the star. Upon impacting the stellar surface, the shocked gas recombines and emits hydrogen spectral lines. To characterize the density and temperature of the gas within these accretion streams, we…
The Z Camelopardalis-type Star AY Piscium: Stellar and Accretion Disk Parameters
Zharikov, Sergey; Merc, Jaroslav; Kára, Jan +5 more
We present a new study of the Z Cam-type eclipsing cataclysmic variable AY Piscium with the aim of determining the fundamental parameters of the system and the structure of the accretion flow therein. We use time-resolved photometric observations supplemented by spectroscopy in the standstill, to which we applied our light-curve modeling technique…
TREX: Kinematic Characterization of a High-dispersion Intermediate-age Stellar Component in M33
Williams, Benjamin F.; Gilbert, Karoline M.; Guhathakurta, Puragra +7 more
The dwarf galaxy Triangulum (M33) presents an interesting testbed for studying stellar halo formation: it is sufficiently massive so as to have likely accreted smaller satellites, but also lies within the regime where feedback and other "in situ" formation mechanisms are expected to play a role. In this work, we analyze the line-of-sight kinematic…
CWISE J105512.11+544328.3: A Nearby Y Dwarf Spectroscopically Confirmed with Keck/NIRES
Meisner, Aaron M.; Cushing, Michael C.; Kirkpatrick, J. Davy +14 more
Y dwarfs, the coolest known spectral class of brown dwarfs, overlap in mass and temperature with giant exoplanets, providing unique laboratories for studying low-temperature atmospheres. However, only a fraction of Y dwarf candidates have been spectroscopically confirmed. We present Keck/NIRES near-infrared spectroscopy of the nearby (d ≈ 6-8 pc) …
The Black Hole Candidate Swift J1728.9-3613 and the Supernova Remnant G351.9-0.9
Raymond, John; Ray, Paul S.; Zoghbi, Abderahmen +12 more
A number of neutron stars have been observed within the remnants of the core-collapse supernova explosions that created them. In contrast, black holes are not yet clearly associated with supernova remnants (SNRs). Indeed, some observations suggest that black holes are "born in the dark," i.e., without a supernova explosion. Herein, we present a mu…
Multiple Rings and Asymmetric Structures in the Disk of SR 21
Dong, Ruobing; Tamura, Motohide; Liu, Hauyu Baobab +9 more
Crescent-like asymmetric dust structures discovered in protoplanetary disks indicate dust aggregations. Thus, researching these structures helps us understand the planet formation process. Here we analyze ALMA data of the protoplanetary disk around the T-Tauri star SR 21, which has asymmetric structures that were detected in previous submillimeter…
The Initial Mass Function and Other Stellar Properties Across the Core of the Hydra I Cluster
Feldmeier-Krause, A.; Freedman, W. L.; Lonoce, Ilaria
The Hydra I cluster offers an excellent opportunity to study and compare the relic old stellar populations in the core of its two brightest galaxies. In addition, the differing kinematics of the two galaxies allows a test of the local validity of general scaling relations. In this work, we present a direct comparison employing full spectral fittin…
Planar Magnetic Structures Downstream of Coronal Mass Ejection-driven Shocks in the Inner Heliosphere
Xu, Qi; Feng, Xueshang; Shen, Zhenning +7 more
Planar magnetic structures (PMSs), characterized by interplanetary magnetic field vectors remaining parallel to a specific plane, are commonly observed in the solar wind, especially in the sheath region of interplanetary coronal mass ejections (ICMEs). In this study, PMS events in the 2 hr regions downstream of ICME-driven shocks were investigated…
Ion Energization and Thermalization in Magnetic Reconnection Exhaust Region in the Solar Wind
Verscharen, Daniel; He, Jiansen; Fedorov, Andrey +7 more
Plasma energization and thermalization in magnetic reconnection is an important topic in astrophysical studies. We select two magnetic reconnection exhausts encountered by Solar Orbiter and analyze the associated ion heating in the kinetic regime. Both cases feature asymmetric plasma merging in the exhaust and anisotropic heating. For a quantitati…
Photospheric and Chromospheric Magnetic Field Evolution during the X1.6 Flare in Active Region NOAA 12192
Guglielmino, S. L.; Romano, P.; Zuccarello, F. +2 more
We report on observations acquired by the Interferometric Bidimensional Spectropolarimeter (IBIS) during SOL2014-10-22T14:02, an X1.6 flare that occurred in active region NOAA 12192, taken in the Fe I 617.30 nm and Ca II 854.2 nm line profiles. We analyze polarization signatures in the Stokes profiles of the two lines across one of the flare ribbo…