Search Publications
The Force-freeness of the Solar Photosphere: Revisit with New Approach and Large Data Sets
Zhang, Mei; Zhang, Haocheng
Although it is generally believed that the solar photosphere is not magnetically force-free owing to its high plasma β, the estimations of force-freeness using observed magnetograms have produced disputable results. Some studies confirmed that the photosphere is largely not force-free whereas some authors argued that the photosphere is not far awa…
Formation of a Massive Lenticular Galaxy Under the Tidal Interaction with a Group of Dwarf Galaxies
Zhang, Chuan-Peng; Xu, Jin-Long; Zhu, Ming +6 more
Based on the atomic-hydrogen (H I) observations using the Five-hundred-meter Aperture Spherical radio Telescope, we present a detailed study of the gas-rich massive S0 galaxy NGC 1023 in a nearby galaxy group. The presence of a H I extended warped disk in NGC 1023 indicates that this S0 galaxy originated from a spiral galaxy. The data also suggest…
New and Improved Lyα Reconstructions for M and K Dwarfs
Loyd, R. O. Parke; France, Kevin; Youngblood, Allison +1 more
The Lyα emission line is the brightest UV emission line in M and K dwarf spectra and serves as an important tool for studies of stellar chromospheres, the interstellar medium, and exoplanet atmospheres. However, Lyα observations have proven difficult due to the strong absorption by the interstellar medium, necessitating a reconstruction of the int…
The Core Starbursts of the Galaxy NGC 3628: Radio Very Long Baseline Interferometry and X-Ray Studies
Yang, Xiaolong; Ou, Ziwei
We present radio very long baseline interferometry (VLBI) and X-ray studies of the starburst galaxy NGC 3628. The VLBI observation at 1.5 GHz reveals seven compact (0.7-7 pc) radio sources in the central ~250 pc region of NGC 3628. Based on their morphology, high radio-brightness temperatures (105-107 K), and steep radio spec…
A Statistical Analysis of Deflection of Coronal Mass Ejections in the Field of View of LASCO Coronagraphs
Gopalswamy, Nat; Yashiro, Seiji; Michalek, Grzegorz +1 more
Coronal mass ejections (CMEs) can generate the most severe geomagnetic disturbances. One of the most critical factors affecting a CME's geoeffectiveness is its trajectory. It is crucial to determine whether and when CME will hit Earth. It is commonly assumed that CMEs experience a deflection of propagation in the corona and in interplanetary space…
A Search for Stellar Siblings of the 200 Myr TOI-251 b Planetary System
Kraus, Adam L.; Barber, Madyson G.; Mann, Andrew W. +4 more
Young planets (<1 Gyr) are helpful for studying the physical processes occurring at the early stage of planet evolution. TOI-251 b is a recently discovered sub-Neptune orbiting a young G dwarf, which has an imprecise age estimation of 40-320 Myr. We select TOI-251 sibling candidates based on kinematics and spatial proximity to TOI-251 and furth…
Fast Outflowing Warm Absorbers in Narrow-line Seyfert 1 Galaxy PG 1001+054 Revealed by HST/COS Spectra
Wang, Junfeng; Zhang, Zhi-Xiang; Fu, Xiao-Dan +1 more
Narrow-line Seyfert 1 (NLS1) galaxies are an important type of active galactic nucleus (AGN), generally expected to be accreting at a high Eddington rate. The properties of their outflows and importance of AGN feedback remain intriguing. We report on the discovery of fast outflowing warm absorbers (WAs) in the NLS1 PG 1001+054 with velocities in t…
Drop in the Hard Pulsed Fraction and a Candidate Cyclotron Line in IGR J16320-4751 Seen by NuSTAR
Rahoui, F.; Tomsick, J. A.; Rodriguez, J. +10 more
We report on a timing and spectral analysis of a 50 ks NuSTAR observation of IGR J16320-4751 (= AX J1631.9-4752), a high-mass X-ray binary hosting a slowly rotating neutron star. In this observation from 2015, the spin period was 1308.8 ± 0.4 s giving a period derivative $\dot{P}\sim 2\times {10}^{-8}$ s s-1 when compared with the perio…
X-Rays Trace the Volatile Content of Interstellar Objects
Wang, Q. Daniel; Cabot, Samuel H. C.; Seligman, Darryl Z.
The nondetection of a coma surrounding 1I/'Oumuamua, the first discovered interstellar object (ISO), has prompted a variety of hypotheses to explain its nongravitational acceleration. Given that forthcoming surveys are poised to identify analogs of this enigmatic object, it is prudent to devise alternative approaches to characterization. In this s…