Search Publications
A Monte Carlo Method for Evaluating Empirical Gyrochronology Models and Its Application to Wide Binary Benchmarks
Buzasi, Derek; Oswalt, T. D.; von Hippel, Ted +3 more
Accurate stellar ages are essential for our understanding of the star formation history of the Milky Way and Galactic chemical evolution, as well as to constrain exoplanet formation models. Gyrochronology, a relationship between stellar rotation and age, appears to offer a reliable age indicator for main-sequence (MS) stars over the mass range of …
The Role of Binarity and Stellar Rotation in the Split Main Sequence of NGC 2422
de Grijs, Richard; Li, Chengyuan; Chen, Li +8 more
In addition to the extended main-sequence turnoffs widely found in young and intermediate-age (~600 Myr to 2 Gyr old) star clusters, some younger clusters even exhibit split main sequences (MSs). Different stellar rotation rates are proposed to account for the bifurcated MS pattern, with red and blue MSs (rMS and bMS) populated by fast and slowly …
Non-LTE Inversion of Prominence Spectroscopic Observations in Hα and Mg II h&k lines
Heinzel, Petr; Schmieder, Brigitte; Jejčič, Sonja +4 more
We continued our investigation of the plasma characteristics of a quiescent prominence that occurred on 2017 March 30. The prominence was observed simultaneously by several instruments, including the Interface Region Imaging Spectrograph (IRIS) and the Multichannel Subtractive Double Pass (MSDP) spectrograph operating at the Meudon solar tower. We…
An X-Ray Study of Coronally Connected Active Eclipsing Binaries
Pandey, J. C.; Singh, Gurpreet
We present a detailed X-ray analysis and imaging of stellar coronae of five coronally connected eclipsing binaries, namely, 44 Boo, DV Psc, ER Vul, XY UMa, and TX Cnc. Both components of these binaries are found to be active. The X-ray light curves of detached and semidetached type systems show eclipsed-like features, whereas no evidence for coron…
Mass-ratio Distribution of Binaries from the LAMOST-MRS Survey
Wang, Luqian; Han, Zhanwen; Chen, Xuefei +7 more
Binary evolution leads to the formation of important objects that are crucial for the development of astrophysics, but the statistical properties of binary populations are still poorly understood. The LAMOST-MRS has provided a large sample of stars to study the properties of binary populations, especially for the mass-ratio distributions and binar…
Effects of Hydrogen versus Helium on Electromagnetic Black Hole Observables
Gammie, Charles F.; Wong, George N.
The centers of our Galaxy and the nearby Messier 87 are known to contain supermassive black holes, which support accretion flows that radiate across the electromagnetic spectrum. Although the composition of the accreting gas is unknown, it is likely a mix of ionized hydrogen and helium. We use a simple analytic model and a suite of numerical gener…
Informing the Cataclysmic Variable Sequence from Gaia Data: The Orbital-period-Color-Absolute-magnitude Relationship
Rix, Hans-Walter; Szkody, Paula; Bloom, Joshua S. +2 more
The orbital-period (P orb) gap in the population of cataclysmic variables (CVs) informs the theoretical narrative of CV evolution, yet a complete understanding of the driving angular momentum loss mechanisms above and below this gap remains elusive. Here we identify, for standard CVs, a new, apparently monotonic relationship between qui…
The Origin of the Vanishing Soft X-Ray Excess in the Changing-look Active Galactic Nucleus Mrk 590
Dewangan, Gulab C.; Laha, Sibasish; Bhalerao, Varun +3 more
We have studied the nature and origin of the soft X-ray excess detected in the interesting changing-look active galactic nucleus (CLAGN) Mrk 590 using two decades of multiwavelength observations from XMM-Newton, Suzaku, Swift, and NuSTAR. In light of vanishing soft excess in this CLAGN, we test two models, "the warm Comptonization" and "the ionize…
Dependence of Energetic Storm Particle Heavy Ion Peak Intensities and Spectra on Source CME Longitude and Speed
Jian, L. K.; Desai, M. I.; Dayeh, M. A. +4 more
We examine variations in energetic storm particle (ESP) heavy ion peak intensities and energy spectra at CME-driven interplanetary shocks. We focus on their dependence with heliolongitude relative to the source region of their associated CMEs, and with CME speed, for events observed in Solar Cycle 24 at the STEREO-A, STEREO-B, and/or ACE spacecraf…
Supersonic Expansion of the Bipolar H II Region Sh2-106: A 3500 Year Old Explosion?
Ginsburg, Adam; Bally, John; Chia, Zen +4 more
Multi-epoch narrowband Hubble Space Telescope images of the bipolar H II region Sh2-106 reveal highly supersonic nebular proper motions that increase with projected distance from the massive young stellar object S106 IR, reaching over ~30 mas yr-1 (~150 km s-1 at D = 1.09 kpc) at a projected separation of ~1.'4 (0.44 pc) from…