Search Publications
Changes in the Near-surface Shear Layer of the Sun
Basu, Sarbani; Antia, H. M.
We use helioseismic data obtained over two solar cycles to determine whether there are changes in the near-surface shear layer (NSSL). We examine this by determining the radial gradient of the solar rotation rate. The radial gradient itself shows a solar-cycle dependence, and the changes are more pronounced in the active latitudes than at adjoinin…
Evidence for Corotation Origin of Super-metal-rich Stars in LAMOST-Gaia: Multiple Ridges with a Similar Slope in the ϕ versus L z Plane
Zhao, Gang; Chen, Yuqin; Zhang, Haopeng
Super-metal-rich (SMR) stars in the solar neighborhood are thought to be born in the inner disk and come to their present location by radial migration, which is most intense at the corotation resonance (CR) of the Galactic bar. In this work, we show evidence for the CR origin of SMR stars in the Large Sky Area Multi-Object Fiber Spectroscopic Tele…
The Pulsating Helium-atmosphere White Dwarfs. I. New DBVs from the Sloan Digital Sky Survey
Kepler, S. O.; Hermes, J. J.; Bell, Keaton J. +4 more
We present a dedicated search for new pulsating helium-atmosphere (DBV) white dwarfs from the Sloan Digital Sky Survey using the McDonald 2.1 m Otto Struve Telescope. In total we observed 55 DB and DBA white dwarfs with spectroscopic temperatures between 19,000 and 35,000 K. We find 19 new DBVs and place upper limits on variability for the remaini…
Intrinsic Shapes of Brightest Cluster Galaxies
Bender, Ralf; Thomas, Jens; Saglia, Roberto P. +5 more
We discuss the statistical distribution of galaxy shapes and viewing angles under the assumption of triaxiality by deprojecting observed surface brightness profiles of 56 brightest cluster galaxies (BCGs) coming from a recently published large deep-photometry sample. For the first time, we address this issue by directly measuring axis ratio profil…
Central Black Hole Mass in the Distant Tidal Disruption Event Candidate of Swift J2058.4+0516
Zhang, XueGuang
In this article, the central black hole (BH) mass in the distant tidal disruption event (TDE) of Swift J2058.4+0516, the second candidate of relativistic jet birth related to a TDE, is estimated. Swift J2058.4+0516 has quite different BH masses estimated through different indirect methods in the literature. Therefore, it is necessary and interesti…
Large Impact of the Mg II h and k Incident Radiation Change on Results of Radiative Transfer Models and the Importance of Dynamics
Heinzel, Petr; Gunár, Stanislav; Koza, Július +1 more
We demonstrate that changes in the incident radiation in Mg II h and k lines have a significant impact on the results of radiative transfer modeling of prominence-like plasmas. To uncover the extent of this impact and allow easy comparison, here we study two cases, one representing the minimum of the solar activity and the other corresponding to t…
Rotating Solar Models in Agreement with Helioseismic Results and Updated Neutrino Fluxes
Yang, Wuming
Standard solar models (SSMs) constructed in accordance with old solar abundances are in reasonable agreement with seismically inferred results, but SSMs with new low-metal abundances disagree with the seismically inferred results. The constraints of neutrino fluxes on solar models exist in parallel with those of helioseismic results. The solar neu…
Demographics of the M-star Multiple Population in the Orion Nebula Cluster
Reiter, Megan; Meyer, Michael R.; De Furio, Matthew +4 more
We present updated results constraining multiplicity demographics for the stellar population of the Orion Nebula Cluster (ONC, a high-mass, high-density star-forming region), across primary masses 0.08-0.7 M ⊙. Our study utilizes archival Hubble Space Telescope data obtained with the Advanced Camera for Surveys using multiple filters (G…
The Long Stare at Hercules X-1. I. Emission Lines from the Outer Disk, the Magnetosphere Boundary, and the Accretion Curtain
Fabian, A. C.; Reynolds, C. S.; Pinto, C. +11 more
Hercules X-1 is a nearly edge-on accreting X-ray pulsar with a warped accretion disk, precessing with a period of about 35 days. The disk precession allows for unique and changing sightlines toward the X-ray source. To investigate the accretion flow at a variety of sightlines, we obtained a large observational campaign on Her X-1 with XMM-Newton (…
Thermal Comptonization in a Changing Corona in the Changing-look Active Galaxy NGC 1566
Dewangan, Gulab Chand; Tripathi, Prakash
We present broadband UV/X-ray spectral variability of the changing-look active galactic nucleus (AGN) NGC 1566, based on simultaneous near-ultraviolet and X-ray observations performed by the XMM-Newton, Swift, and NuSTAR satellites at five different epochs during the declining phase of the 2018 outburst. We found that the accretion disk, soft X-ra…