Search Publications
On the metallicity gradient in the Galactic disk
Loktin, Alexander; Popova, Maria
The problem of the chemical composition gradient in the Galactic disk is studied based on a sample of metallicity estimates of open star clusters, using Gaia DR2-improved distance estimates. A clearly non-monotonic variation was observed in the average metallicity of clusters with increasing Galactocentric distance. One can clearly see the metalli…
A study on the dynamic spectral indices for SEP events on 2000 July 14 and 2005 January 20
Le, Gui-Ming; Zhao, Ming-Xian
We have studied the dynamic proton spectra for the two solar energetic particle (SEP) events on 2000 July 14 (hereafter GLE59) and 2005 January 20 (hereafter GLE69). The source locations of GLE59 and GLE69 are N22W07 and N12W58 respectively. Proton fluxes >30 MeV have been used to compute the dynamic spectral indices of the two SEP events. Our …
Discovery of extended structures around two evolved planetary nebulae M2-55 and Abell 2
Zhang, Yong; Hsia, Chih-Hao; Zhang, Xi-Liang +1 more
We report a multi-wavelength study of two evolved planetary nebulae (PNs)M2-55 and Abell 2. Deep optical narrow-band images ([O III], Hα, and [N II]) of M2-55 reveal two pairs of bipolar lobes and a new faint arc-like structure. This arc-shaped filament around M2-55 appears as a well-defined boundary from southwest to southeast, strongly suggestin…
On the correctness of orbital solutions obtained from a small set of points. Orbit of HIP 53731
Mitrofanova, Arina; Dyachenko, Vladimir; Beskakotov, Anatoly +4 more
HIP 53731 is a binary consisting of stars of the spectral types K0 and K9. The orbit of this object was constructed previously by Cvetković et al. and improved by Tokovinin. It should be noted that there is a 180° ambiguity in the position angles of some published measurements. Speckle interferometric observations were obtained in 2007-2020 (21 me…
The evolutionary status of chemically peculiar eclipsing binary star DV Boo
Aliçavuş, F.; Kahraman Aliçavuş, Filiz
Eclipsing binary systems are unique stellar objects to examine and understand stellar evolution and formation. Thanks to these systems, the fundamental stellar parameters (mass, radius) can be obtained very precisely. The existence of metallic-line (Am) stars in binaries is noticeably common. However, the known number of Am stars in eclipsing bina…
The first photometric investigation of the contact binary OQ Cam
Guo, Ya-Ni; Li, Kai; Xia, Qi-Qi +3 more
The first charge-coupled device photometric light curves in B, V, Rc, and Ic bands of the short-period contact binary star OQ Cam are presented. Through analyzing the light curves with the Wilson-Devinney code, it is found that OQ Cam is a W-type shallow contact binary star with a contact degree of f = 20.2%. Based on the O -…
Identification of temperature anomaly RR Lyrae stars in LAMOST survey, misclassification and binarities
Li, Lin-Jia; Qian, Sheng-Bang; Zhu, Li-Ying +2 more
RR Lyrae stars, a well-known type of pulsating variable stars, have been known about for more than a century. A large amount of photometric data on RR Lyrae stars has been accumulated by space- and ground-based sky surveys, but the spectral data are relatively poor. Fortunately, the LAMOST sky survey project provides an opportunity to view them fr…
BV (RI)c photometric study of three variable PMS stars in the field of V733 Cephei
Ibryamov, Sunay; Semkov, Evgeni; Peneva, Stoyanka +1 more
This paper reports results from the first long-term BV (RI)c photometric CCD observations of three variable pre-main-sequence stars collected during the period from February 2007 to January 2020. The investigated stars are located in the field of the PMS star V733 Cep within the Cepheus OB3 association. All stars from our study show rap…
Conditions for galaxy quenching at 0.5 < z < 2.5 from CANDELS: compact cores and environment
Gu, Qiu-Sheng; Gu, Yi-Zhou; Ge, Xue +2 more
We investigate two classes of conditions for galaxy quenching at 0.5 < z < 2.5 based on the structural scaling relations of galaxies in the five Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) fields: the formation of a compact core and the environment. We confirm that in the entire redshift range, massive quiescent …
Spectral properties of the surface reflectance of the northern polar region of Mercury
Diep, Pham Ngoc; Ngoc, Nguyen Bich; Bott, Nicolas
We analyze MESSENGER reflectance measurements covering the northern polar region of Mercury, the least studied region of the northern mercurian hemisphere. We use observations from the Mercury Dual Imaging System Wide-Angle Camera (MDIS/WAC) and the Mercury Atmospheric and Surface Composition Spectrometer (MASCS/VIRS) to study the spectral depende…