Search Publications
The Temperature and Density of a Solar Flare Kernel Measured from Extreme-ultraviolet Lines of O IV
Young, Peter R.
Previously unexplored diagnostics of O IV in the extreme-ultraviolet region 260–280 Å are used to derive a temperature and density for a solar flare kernel observed on 2012 March 9 with the Extreme-ultraviolet Imaging Spectrometer on the Hinode satellite. Seven lines from the 2s2p 2–2s2p3s transition array between 271.99 and 272.31 Å ar…
A Comparative Study of Two Contrasting Cosmic-Ray Events Caused by Solar Eruptions from NOAA AR 12673 in 2017 September
Zhang, Shuang Nan; Zhang, Ping; Yu, Xiao Xia +3 more
Two major solar eruptions on AR 12673 produced a Forbush decrease (FD) event (reduction of cosmic rays) on 2017 September 8 and ground-level enhancement (GLE; enhancement of cosmic rays) on 2017 September 10. The occurrence of two contrasting cosmic-ray events within 2 days that are associated with two similar X-class solar flares (X9.3 and X8.2) …
An Outflow-driven Water Maser Associated with Positive Black Hole Feedback in the Dwarf Galaxy Henize 2–10
Darling, Jeremy; Reines, Amy E.; Momjian, Emmanuel +1 more
Henize 2–10 is a dwarf galaxy experiencing positive black hole (BH) feedback from a radio-detected low-luminosity active galactic nucleus. Previous Green Bank Telescope (GBT) observations detected a H2O "kilomaser" in Henize 2–10, but the low angular resolution (33″) left the location and origin of the maser ambiguous. We present new Ka…
X-Ray, UV, and Optical Observations of Proxima Centauri's Stellar Cycle
Slavin, Jonathan D.; do Nascimento, José-Dias; Saar, Steven H. +3 more
Proxima Cen (GJ 551; dM5.5e) is one of only about a dozen fully convective stars known to have a stellar cycle, and the only one to have long-term X-ray monitoring. A previous analysis found that X-ray and mid-UV observations, particularly two epochs of data from Swift, were consistent with a well-sampled ∼7 yr optical cycle seen in All Sky Automa…
An X-Ray Significantly Variable, Luminous, Type 2 Quasar at z = 2.99 with a Massive Host Galaxy
Marchesi, Stefano; Gilli, Roberto; Zhao, Xiurui +8 more
We present a comprehensive X-ray analysis and spectral energy distribution (SED) fitting of WISEA J171419.96+602724.6, an extremely luminous type 2 quasar at z = 2.99. The source was suggested as a candidate Compton-thick (column density N H > 1.5×1024 cm‑2) quasar by a short XMM-Newton observation in 2011. We r…
KM UMa: An Active Short-period Detached Eclipsing Binary in a Hierarchical Quadruple System
Meng, Fangbin; Zhu, Liying; Liu, Nianping +4 more
The first detailed photometric and spectroscopic analysis of the G-type eclipsing binary KM UMa is presented, which indicates that the system is a short-period detached eclipsing binary. The radial velocity curves were calculated using the cross-correlation function method based on Large Sky Area Multi-Object Fiber Spectroscopic Telescope, Sloan D…
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…