Publications
Section: PZ: main journal
|
The optical transient MASTER OT J095321.02+202721.2, discovered in 2014, was not classified or confirmed as a supernova. We present the light curve of this object which allows us to classify it as a type II-L supernova with the absolute magnitude at maximum brightness M_R about -19.4 mag.
We present our analysis of new photometric and spectroscopic data for a poorly studied star with an uncertain variability type (BY Dra or EW), ZTF J021857.72+585950.1. The observations were carried out with the 0.6-m and 2.5-m telescopes of the Caucasian Mountain Observatory and the 1.25-m telescope of the Crimean Astronomical Station of the Sternberg Astronomical Institute (Lomonosov Moscow State University) in 2019 - 2024. We found a period of 0.279 d and demonstrated that brightness variations resulted from rotation of a spotted chromospherically active star of the BY Dra type, which is consistent with the AAVSO classification. Based on our low-resolution spectra, we classified the star as K1V and found profile variations of the Halpha line both from night to night and during a single night. We also estimated the interstellar extinction A_V = 0.27 mag and distance to the star d = 154 pc.
The results of light curve analysis are presented for the old Nova V728 Sco. The object is a high-inclination system with an orbital period of 3.32 hours. The observed light curves of V728 Sco from photometric observations of C. Tappert et al. performed in 2012 were fitted with synthetic light curves to solve for the parameters of this system. We found the system parameters providing the shape of the synthetic light curve most closely matching the observed one applying the Nelder - Mead method. Contributions to the combined flux from the system components: white dwarf, red dwarf, accretion disk with the hot spot on its lateral surface, and hot line are determined for active and quiet states in the frame of the combined model developed by T.S. Khruzina in 2011.
High precision photometric observations of the bright Nova V1112 Per at early stages after its outburst are presented. We found the time of the star's maximum brightness, estimated its interstellar extinction using empirical formulas. Our data made it possible to determine the mass of white dwarf M_(wd) = 0.82+/-0.07 M_(Sun) and the distance to the star d = 5.2 +/- 0.4 kpc. Fast variability at early stages was detected.
Six binary and candidate binary stars in the fields of V0873 Per and CV Boo were found using archive observations of the Mt.~Maidanak Astronomical Observatory. (1) 2MASS J02465266+4125290 is a detached eclipsing binary with the period of P=5.9436+/-0.0027 d. (2) TYC 2853-60-1 is a detached eclipsing binary with the period of P=1.79+/-0.01 d. (3) 2MASS J02475840+4116103 is an ellipsoidal binary system with the period of P=0.30744+/-0.00005 d. (4) 2MASS J02464361+4120282 is a BY Dra-type binary star with the rotational period of P=12.18+/-0.06 d. (5) 2MASS J02465622+4117392 is an ellipsoidal binary system with the period of P=4.022+/-0.009 d. (6) 2MASS J15273711+3703070 is an ellipsoidal and/or RS CVn binary system with the period of P=0.3307+/-0.0002 d. Three of these stars exhibit chromospheric activity.
We derive RR Lyrae period - metallicity - mid-infrared
luminosity relations in the WISE W1 and W2 bands based on
intensity-mean W1 and W2 magnitudes computed from
intensity-mean Gaia G_(BP) and G_(RP) magnitudes and known
metallicity [Fe/H] for ~5000 field RR~Lyrae variables and
~700 variables in 24 globular clusters:
The recent Gaia DR3 all-sky list of candidates for eclipsing binaries including 2,184,477 sources, and the list of probable members of galactic clusters by Hunt and Reffert (2024), are used to identify eclipsing binary stars -- members of star clusters, and to compare their general characteristics to those of eclipsing binaries in the galactic field. We find that the distributions over orbital frequencies notably differ from each other due to dynamic evolution of binary star orbits in galactic clusters. On the other hand, the distributions over the depth ratio of minima in clusters and in galactic field are similar, which supports the universality of pairing algorithm during binary star formation.
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. |
