Search Publications
Analysis of X-Ray Emission from OB Stars. IV. About X-Ray Emission from Inhomogeneous Winds of OB Stars
Ryspaeva, Elizaveta; Kholtygin, Alexander
We study the origin of X-ray emission from OB stars due to collisions of stellar winds and/or inhomogeneities in the winds. The low-resolution X-ray spectra of a big sample of OB stars were fitted by both the stationary APEC/MEKAL models and by this model with an additional PSHOCK component describing the nonstationary X-ray emission. These spectr…
An Improved Pair Method to Probe the Dust Extinction Law
Gao, Jian; Ren, Yi; Wang, Yuxi +1 more
Dust extinction law is crucial to recover the intrinsic energy distribution of celestial objects and infer the characteristics of interstellar dust. Based on the traditional pair method, an improved pair method is proposed to model the dust extinguished spectral energy distribution (SED) of an individual star. Instead of the mathematically paramet…
Probing the Variation of Reverberation Lags along with X-Ray Flux in the AGN Mrk 704
Sriram, K.; Choi, C. S.; Agrawal, Vivek K. +2 more
Understanding the variation of lags with respect to the X-ray flux is important to explore the geometry of the inner region of the accretion disk in AGNs. We performed frequency-lag, energy-lag and spectral studies for two sets of observations, in order to investigate the variations in lags with respect to X-ray flux in the AGN source Mrk 704 usin…
First Detailed Photometric Investigation on the Nature of Contact Binary System AA Cet
Yıldırım, M. F.; Soydugan, F.
The TESS light curve (LC) of the marginal contact binary AA Cet was analyzed simultaneously with the radial velocity and the orbital period (OP) change of the system was investigated. The physical parameters of the system were obtained by analyzing the LC of AA Cet with the Wilson-Devinney method, and the absolute parameters of the components were…
A Comparison of Co-temporal Vector Magnetograms Obtained with HMI/SDO and SP/Hinode
Zhang, Mei; Zhang, Haocheng; Jiang, Chengqing
Accurate measurement of magnetic fields is very important for understanding the formation and evolution of solar magnetic fields. Currently, there are two types of solar magnetic field measurement instruments: filter-based magnetographs and Stokes polarimeters. The former gives high temporal resolution magnetograms and the latter provides more acc…
Full-frame Data Reduction Method: A Data Mining Tool to Detect the Potential Variations in Optical Photometry
Zhou, Hao; Dai, Zhi-Bin; Cao, Jin
A Synchronous Photometry Data Extraction (SPDE) program, performing indiscriminate monitoring of all stars appearing in the same field of view of an astronomical image, is developed by integrating several Astropy affiliated packages to make full use of time series observed by traditional small/medium aperture ground-based telescopes. The complete …
On the Neutron Star/Black Hole Mass Gap and Black Hole Searches
Shao, Yong
Mass distribution of black holes in low-mass X-ray binaries previously suggested the existence of a ~2-5 M ⊙ mass gap between the most massive neutron stars and the least massive black holes, while some recent evidence appears to support that this mass gap is being populated. Whether there is a mass gap or not can potentially shed light…
Discovery of Extended Structure Around Open Cluster COIN-Gaia 13 Based on Gaia EDR3
Chen, Li; Zhong, Jing; Li, Jing +2 more
COIN-Gaia 13 is a newly discovered open cluster revealed by Gaia DR2 data. It is a nearby open cluster with a distance of about 513 pc. Combined with the five-dimensional astrometric data of Gaia EDR3 with higher accuracy, we use the membership assignment algorithm (pyUPMASK) to determine the membership of COIN-Gaia 13 in a large extended spatial …
Candidate Eclipsing Binary Systems with a δ Scuti Star in Northern TESS Field
Kahraman Aliçavuş, F.; Aliçavuş, F.; Ekinci, Ö. +4 more
The existence of pulsating stars in eclipsing binaries has been known for decades. These types of objects are extremely valuable systems for astronomical studies as they exhibit both eclipse and pulsation variations. The eclipsing binaries are the only way to directly measure the mass and radius of stars with a good accuracy (≤1%), while the pulsa…
A Possible 250 s X-Ray Quasi-periodicity in the Fast Blue Optical Transient AT2018cow
Tao, Lian; Zhang, Liang; Shu, Xinwen +11 more
The fast blue optical transients (FBOTs) are a new population of extragalactic transients of unclear physical origin. A variety of mechanisms has been proposed including failed supernova explosion, shock interaction with a dense medium, young magnetar, accretion onto a compact object and stellar tidal disruption event, but none is conclusive. Here…