Search Publications
Detection of Two Totally Eclipsing B-type Binaries with Extremely Low Mass Ratios
Qian, Shengbang; Li, Fuxing; Zang, Lei +1 more
The detection of O- and B-type stars with extremely low-mass companions is very important for understanding the formation and evolution of binary stars. However, finding them remains a challenge because the low-mass components in such systems contribute such small flux to the total. During our search for pulsations among O- and B-type stars using …
The Deeper Studies of IC 2488 and IC 2714
Li, Xu-Zhi; Zhu, Qing-Feng; Xu, Xiao-Hui +2 more
In this paper, we use two methods, an algorithm of the density-based spatial clustering of applications with noise combined with the Gaussian mixture model, and the maximum likelihood method, to study two open clusters: IC 2488 and IC 2714 with Gaia Data Release 3 data. We compare the two methods in terms of cluster star number, isochrone fitting,…
Investigating Ionization in the Intergalactic Medium
Borthakur, Sanchayeeta; Koplitz, Brad; Ramesh, Anjali
The intergalactic medium (IGM) contains >50% of the baryonic mass of the Universe, yet the mechanisms responsible for keeping the IGM ionized have not been fully explained. Hence, we investigate ion abundances from the largest blind QSO absorption catalog for clouds that show C IV, N V, and O VI simultaneously. The wavelength range of present U…
Lyman Limit System with O VI in the Circumgalactic Environment of a Pair of Galaxies
Wendt, Martin; Muzahid, Sowgat; Narayanan, Anand +3 more
We report on the analysis of a multiphase Lyman limit system (LLS) at z = 0.39047 identified toward the background quasar FBQS J0209–0438. The O VI doublet lines associated with this absorber have a different profile from the low-ionization metals and H I. Ly α has a very broad H I (b ≈ 150 km s‑1) component well-aligned with one of the…
Flare-accelerated Electrons in the Kappa Distribution from X-Ray Spectra with the Warm-target Model
Kontar, Eduard P.; Luo, Yingjie; Bhattacharjee, Debesh
X-ray observations provide important and valuable insights into the acceleration and propagation of nonthermal electrons during solar flares. Improved X-ray spectral analysis requires a deeper understanding of the dynamics of energetic electrons. Previous studies have demonstrated that the dynamics of accelerated electrons with a few thermal speed…
Magnetic Fields in a Sample of Planet-hosting M Dwarf Stars from Kepler, K2, and TESS Observed by APOGEE
Wanderley, Fábio; Cunha, Katia; Smith, Verne V. +8 more
Stellar magnetic fields have a major impact on space weather around exoplanets orbiting low-mass stars. From an analysis of Zeeman-broadened Fe I lines measured in near-infrared SDSS/APOGEE spectra, mean magnetic fields are determined for a sample of 29 M dwarf stars that host closely orbiting small exoplanets. The calculations employed the radiat…
Molecular Hydrogen Line Identifications in Solar Flares Observed by IRIS: Lower Atmospheric Structure from Radiometric Analysis
Jaeggli, Sarah A.; Daw, Adrian N.
A rich spectrum of molecular hydrogen (H2) emission lines is seen in sensitive observations from the far-ultraviolet (FUV) channels of the Interface Region Imaging Spectrograph (IRIS) during flare activity in solar active region NOAA Active Region 11861. Based on this observation, we have determined 37 new line identifications by compar…
Rotational Velocities and Radii Estimates of Low-mass Pre-main-sequence Stars in NGC 2264
Rhode, Katherine L.; Rebull, Luisa M.; Gray, Laurin M. +2 more
Investigating the angular momentum evolution of pre-main-sequence (PMS) stars provides important insight into the interactions between Sun-like stars and their protoplanetary disks, and the timescales that govern disk dissipation and planet formation. We present projected rotational velocities (v sin i values) of 254 T Tauri stars (TTSs) in the ∼3…
Long-term Evolution in Ionization of Ejecta Illuminated by Eta Carinae
Corcoran, Michael F.; Moffat, Anthony F. J.; Damineli, Augusto +6 more
Changes in the flux and spectrum of Eta Carinae (η Car) since 1900 have been attributed to the evolution of the central binary by some. Others suggest evolution in the occulting ejecta. The brightness jump in the 1940s, which coincided with the appearance of narrow forbidden emission lines, may have been caused by the clearing and ionization of in…
On the Influence of the Solar Wind on the Propagation of Earth-impacting Coronal Mass Ejections
Gopalswamy, Nat; Srivastava, Nandita; Kumar, Sandeep +1 more
Coronal mass ejections (CMEs) are subject to changes in their direction of propagation, tilt, and other properties as they interact with the variable solar wind. We investigated the heliospheric propagation of 15 Earth-impacting CMEs observed during 2010 April to 2018 August in the field of view (FOV) of the Heliospheric Imager (HI) on board the S…