Publications
Section: PZ: main journal
|
Photometric observations of SNe 2012ch and 2012fs show light curves characteristic of type II-P Supernovae. The interstellar extinction for both SNe was estimated by comparison of their color curves with those for well-studied SNe II-P. The absolute magnitudes at the plateau stage are M_R=-17.1 for SN 2012ch and M_R=-16.9 for SN 2012fs, which is close to mean values for the objects of this class. We performed modeling of the light curves of SN 2012ch with the STELLA code, the optimal model has the following parameters: total mass 19M(Sun), radius 900R(Sun), explosion energy 1.5 x 10^(51) erg, mass of (56)Ni 0.07M(Sun).
We estimated the apsidal motion rate in the eclipsing binary system V1437 Cas using TESS light curves d(omega)/dt=0.252+/-0.025 deg/yr. Existing TESS light curves of the system contain 4 extremely deep minima of unknown nature.
In January 1924, Ejnar Hertzsprung discovered a new variable star, DH Car. As it later turned out, this was the first discovery of a flaring red dwarf, type UV Cet in current classification. I present the first determination of the rotation period of DH Car from data acquired with TESS orbital observatory. The period is 0.89 days.
We present photometric BVRI observations of type II SN 2019osl covering 177 days. We determine the dates and magnitudes at maximum light and estimate interstellar extinction by comparison of its color curves with that for a sample of SNe II. The maximum absolute magnitude M_V = -17.9 mag is about 1.2 mag brighter than the mean value for SNe II. The host galaxy UGC 3115 is classified as a lenticular galaxy, but we show that this classification is erroneous, because the images of the galaxy from Pan-STARRS survey clearly reveal a spiral structure.
We present a new Name-List of variable stars containing information on 1610 variable stars in 31 globular star clusters, in four constellations (Pavo - Sagittarius), that now get their names in the system of the General Catalogue of Variable Stars (GCVS). Also, GCVS names are assigned to 6 recent Novae and one young variable star in our Galaxy.
We present our study of 2MASS J23453766+7134365, an eclipsing variable star with a possible pulsating component, from a field in Cepheus. The star exhibits V-shaped eclipses with a depth of approximately 0.25 mag in the V band every 2.44 days; secondary minima are not detected. Also, sinusoidal brightness variations are detected with an amplitude of less than 0.1 mag and a period of 0.6791 days. They appear and disappear quasi-periodically with a characteristic time of several days. For the study of this star, we used the archive of Astrosib RC500 telescope (Mt. Terskol observatory). We conducted follow-up observations with the RC600 telescope (Caucasian Mountain Observatory) and Astrosib RC500 telescope (INASAN Kislovodsk observatory). Also, we used photometric data from the ZTF, ASAS-SN, and TESS surveys.
I present the second part of the catalog of newly detected Multi-Mode Radially Pulsating (MMRP) variable stars. For these stars, pulsations in the fundamental, first-, second-, or third-overtone modes were detected. This paper includes 60 double- and multi-mode stars (numbered from MMRP-051 to MMRP-110). Variability types determined for these stars are RR Lyrae variables and high-amplitude Scuti (HADS) stars. In addition, one of the previously studied stars, MMRP-010, was reclassified. I analyzed all observations available for these stars in the ASAS-SN and ZTF online public archives using the period-search software developed by Dr. V.P. Goranskij for Windows environment. Light elements and parameters of oscillations were determined.
Despite having different astronomical characteristics, Mira variables and ultra-cool dwarfs frequently show similar red colors, which could result in photometric misclassification. This study uses photometric data from the WISE, 2MASS, and Pan-STARRS surveys to construct color-based selection criteria for red dwarfs, brown dwarfs, and Mira variables. Analyzing the color indices, we developed empirical rules that separate these objects with an overall classification accuracy of approximately 91% - 92%. While the differentiation between red dwarfs and both Mira variables and brown dwarfs is effective, challenges remain in distinguishing Mira variables from brown dwarfs due to overlapping color indices. The robustness of our classification technique was validated by means of bootstrap analysis, highlighting the significance of color indices in large photometric surveys for stellar classification.
This study presents parameters of several poorly studied eclipsing variable stars with elliptical orbits. The data were obtained from solution of our own long-term photometric observations.
For both periods of the bimodal Cepheid V367 Sct, O - C diagrams spanning a 113-year time interval are constructed. The O - C diagrams have the form of parabolas, allowing quadratic ephemerides and evolutionary period change rates to be determined for the first time, dP(Fu)/dt=+0.233 (+/- 0.020) s/yr and dP(1O)/dt=+0.244 (+/- 0.025) s/yr, for the fundamental tone and first overtone of V367 Sct, respectively, which are consistent with the results of theoretical computations for the third crossing of the instability strip. The test for stability of pulsations proposed by Lombard and Koen confirmed the reality of the evolutionary change of the periods. |
