Search Publications
Online Catalog of Activity Events of Solar Cycle 24 Related to Active Regions
Tsvetkov, Tsvetan; Petrov, Nikola; Nakeva, Yoana
We present a statistical study on the relationship of solar dynamic events (solar flares and coronal mass ejections) with active regions during Solar Cycle 24 (December 2008–December 2019). Combining data from NOAA Space Weather Prediction Center and observations of Large Angle and Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospher…
Deriving physical parameters of unresolved star clusters. VIII. Limits of aperture photometry for star cluster studies
Stonkutė, Rima; Vansevičius, Vladas; Kriščiūnas, Eimantas +2 more
Context. Recently, it has been noticed that the discrepancies in the integrated colour indices (CIs) between star clusters and models are mostly due to the projection of bright stars in the apertures. In order to reduce this problem, the method of adaptive aperture photometry has been proposed. This method has been applied to star clusters from th…
X-ray plasma flow and turbulence in the colliding winds of WR140
Hamaguchi, Kenji; Miyamoto, Asca; Sugawara, Yasuharu +5 more
We analyse the XMM-Newton RGS spectra of Wolf-Rayet (WR) 140, an archetype long-period eccentric WR+O colliding wind binary. We evaluate the spectra of O and Fe emission lines and find that the plasmas emitting these lines have the largest approaching velocities with the largest velocity dispersions between phases 0.935 and 0.968 where the inferio…
SOFIA/upGREAT far-infrared spectroscopy of bright rimmed pillars in IC 1848
Wiesemeyer, Helmut; Güsten, Rolf; Seo, Youngmin +4 more
Using the upGREAT instrument on SOFIA, we imaged the [C II] 158 µm fine structure line emission in bright-rimmed pillars located at the southern edge of the IC 1848 H II region, and carried out pointed observations of the [O I] 63 and 145 µm fine structure lines toward selected positions. The observations are used to characterize the morphology, v…
Time Variation of the Solar Tachocline
Basu, Sarbani; Korzennik, Sylvain G.; Andrade de Aguiar, Wesley Antônio Machado
We have used solar oscillation frequencies and frequency splittings obtained over solar cycles 23 and 24 and the rising phase of solar cycle 25 to investigate whether the tachocline properties (the change in the rotation rate across the tachocline. i.e., the jump, the width, and the position) show any time variation. We confirm that the change in …
MK-like spectral classification for hot subdwarf stars with LAMOST spectra
Lei, Zhenxin; Zou, Xuan
An MK-like spectral classification has been conducted for 1224 hot subdwarf stars with LAMOST DR9 low-resolution spectra. The whole sample was divided into four categories according to the spectral line characteristics: He-normal, He-weak, He-strong C, and He-strong. Each selected spectrum was assigned a spectral class, a luminosity class, and a h…
A Special Kind of Interplanetary Coronal Mass Ejection
Zhao, G. Q.; Zhao, Y.; Li, H. B. +3 more
It is generally believed that coronal mass ejections (CMEs) have magnetic flux rope structures because of their helical shapes. However, only about 30%–40% of interplanetary CMEs (ICMEs) have a local magnetic flux rope structure. The usual explanations are that the spacecraft only crossed the flank of the ropes and failed to detect the complete ma…
A Search for Low-amplitude Periodic Brightness Variations in HD 168 443
Bondar', N. I.; Shlyapnikov, A. A.
The paper presents the results of studying light curves of the star HD 168443 obtained from the ground-based and space photometric observations within the ASAS, KWS surveys, and the Hipparcos mission from 1990 to 2020. During 30 years of observations, the average annual brightness of the star remained constant within the measurement errors, the me…
Two dynamically discovered compact object candidate binary systems from LAMOST low-resolution survey
Gu, Wei-Min; Yi, Tuan; Zhang, Zhi-Xiang +3 more
We report two binary systems, LAMOST J035540 + 381550 (hereafter J035540) and LAMOST J035916 + 400732 (hereafter J035916), identified through the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) low-resolution survey (LRS). Each of these two systems contains an M-type star orbiting with a invisible compact object candidate. Follo…
Light Curves and Period Analysis of Beta Lyrae Stars
Mennickent, R. E.; Garcés, J.; Cortés, C. C. +1 more
We present the light-curve period analysis of 36 Beta Lyrae stars from the OMC Archive. We check the reference period of the sample by applying the phase dispersion minimization periodogram. From our research, we determine the orbital period of five stars in the sample. One of them is CP Psc, showing a prominent hump in the light curve before the …