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Multiepoch Optical Spectroscopy of the Post-AGB Star HD 161796
Puķītis, Kārlis; Začs, Laimons; Grankina, Aija
The evolutionary rate of the pulsating post-asymptotic giant branch (post-AGB) star HD 161796 was suspected to be high. Spectra of HD 161796 acquired during a time span of 18 yr are analyzed with the main goal of determining the evolutionary increase in temperature and comparing it with the latest post-AGB star evolutionary models. Inspection of t…
A New Method for Retrieving Electron Density Profiles from the MARSIS Ionograms
Le, Huijun; Liu, Libo; Chen, Yiding +7 more
The Martian ionosphere was actively detected by Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) aboard the Mars Express. The detected echo signal of the MARSIS at an epoch is presented as a function of frequency and time delay to form an ionogram. Some MARSIS ionograms have been processed to obtain the electron density profiles…
Planet Four: Derived South Polar Martian Winds Interpreted Using Mesoscale Modeling
Schwamb, Megan E.; Michaels, Timothy I.; Lintott, Chris J. +3 more
For the first time, model-derived and imagery-derived wind directions and speeds have been compared in Mars's south polar region. Seasonal fan-shaped deposits are routinely observed by HiRISE in the polar regions. They are widely accepted to result from CO2 gas jet eruptions. Fan lengths, sizes, and shapes can provide information about …
Star and Cluster Formation in the Sh2-112 Filamentary Cloud Complex
Chen, Wen Ping; Sun, Yan; Mondal, Soumen +1 more
We present the star formation activity around the emission nebula Sh2-112. At a distance of ~2.1 kpc, this H II complex, itself 3 pc in radius, is illuminated by the massive star (O8 V) BD+45 3216. The associated molecular cloud extends in angular scales of 2.°0 × 0.°83, corresponding to linear sizes of 73 pc by 30 pc, along the Galactic longitude…
Response of the Fe Kα line emission to the X-ray continuum variability in the changing-look active galactic nucleus NGC 1566
Shu, X. W.; Wang, J. X.; Jiang, N. +5 more
NGC 1566 is a changing look AGN known to exhibit recurrent X-ray outbursts with each lasting for several years. The most recent X-ray outburst is observed on 2018, with a substantial increase of 2-10 keV flux by a factor of ∼24 than the historical minimum. We re-analyze the XMM-Newton and NuSTAR observations covering the pre-outburst, outburst and…
Measurements of chromospheric Mg I emission lines of zero-age main-sequence stars
Itoh, Yoichi; Yamashita, Mai
The chromosphere is the active atmosphere in which energetic eruption events, such as flares, occur. Chromospheric activity is driven by the magnetic field generated by stellar rotation and convection. The relationship between chromospheric activity and the Rossby number, the ratio of the rotational period to the convective turnover time, has been…
S-type Stars Discovered in Medium-resolution Spectra of LAMOST DR9
Luo, A. -Li; Li, Yin-Bi; Wang, Rui +5 more
In this paper, we report on 606 S-type stars identified from Data Release 9 of the LAMOST medium-resolution spectroscopic (MRS) survey; 539 of them are reported for the first time. The discovery of these stars is a three-step process, i.e., selecting with ZrO-band indices greater than 0.25, excluding non-S-type stars with the iterative Support Vec…
The Frequency-Domain Characterization of Cosmic Ray Intensity Variations Before Forbush Decreases Associated With Geomagnetic Storms
He, Fei; Wang, Cong; Zhang, Xiaoxin +2 more
Nonrecurrent geomagnetic storms caused by Coronal Mass Ejection (CME) can induce serious impacts on space- and ground-based equipment. However, these nonrecurrent geomagnetic storms are hard to predict since CMEs are not periodic. Previous studies have shown that the variations of Cosmic Ray Intensity (CRI) before nonrecurrent storms may forebode …
Comparing reflection and absorption models for the soft X-ray variability in the NLS1 AGN UGC 11763
Jiang, Jiachen; Gallo, Luigi C.; Grupe, Dirk +1 more
We present a spectral analysis of two XMM-Newton observations of the narrow-line Seyfert 1 galaxy UGC 11763. UGC 11763 shows very different soft X-ray spectral shapes in the two observations separated by 12 yr. Three spectral models are considered to explain the multi-epoch X-ray variability of UGC 11763, one based on the relativistic disc reflect…
J1832.4-1627, the first eclipsing stream-fed intermediate polar
Beuermann, K.; Breitenstein, P.; Schwab, E.
We present a photometric study of the newly discovered eclipsing intermediate polar