The nonlinearity of the transfer function of photon detection by a CCD receiver of an echelle fiber-optic spectrograph of high spectral resolution at the BTA SAO RAS is studied. Local analysis of ...signals in the image of the emission spectrum and correction of data are carried out.
We present a study of the influence of magnetically induced control of external convection in stars of different types, in particular white dwarfs, on their thermal evolution. In the work preceding ...this study, we argued that for the cooling down white dwarf stars that have exhausted the sources of thermonuclear combustion, cessation of convection by a magnetic field significantly slows down their cooling. To test this asertion, we performed an observational program to search for new highly magnetized white dwarfs. The program is described in detail in the same issue of the journal. Our observations, together with the observations of other researchers, allowed us to construct the observed luminosity function of strongly magnetized white dwarfs with stopped convection and compare it with the well-known similar luminosity function of white dwarfs with weak fields that allow effective convective heat removal from their insides. As a result of the model analysis of these functions, the hypothesis that strongly magnetized white dwarfs cool down slower than weakly magnetic ones is confirmed. The article also qualitatively examines the effect of magnetic braking of convection in solar-type stars and cool M-dwarf stars of the Main Sequence on the periodicity of their radiation activity. The geophysical aspect of the problem and the practical application of magnetic field control of the heat removal in electrically conductive media are discussed.
We present the results of observations within the program for the search for new highly magnetized white dwarfs among evolutionary old stars of this class. The program was carried out for two years ...at the 1-m telescope of the SAO RAS. As a result, new white dwarf candidates of different ages with super-strong (several megagauss, tens, hundreds of megagauss) magnetic fields were discovered. These observations, along with the observations of other authors made it possible to make a new estimate of the frequency of occurrence of magnetic white dwarfs among old stars. Our results confirm our earlier assumptions that the frequency of occurrence of far-evolved magnetic white dwarfs with magnetic fields of several megagauss or higher and with the temperatures of less than 10 000 K is at the level of 15% or higher, while the frequency of occurrence of such stars among young white dwarfs does not exceed 4–6%. This fact means that the thermal evolution of the physical properties of magnetic white dwarfs differs from the thermal evolution of their weakly magnetic counterparts.
The light curves for almost 50 thousand stars with magnitudes
have been obtained over 2.5 years at SAO RAS in the process of conducting an exoplanet survey in roughly
-sized fields around the white ...dwarfs WD 0009
501 and GRW
708247. In this paper we present a catalog of variable stars that have been found in the considered regions. Periodogram analysis was used as the main variation search method. The catalog includes 150 periodic variable stars: 113 of them have been known previously, and for the remaining 37 variations have been discovered for the first time. These stars were classified according to the nature of the variations into four eclipsing variable and three pulsating types, as well as rotating stars. We present the periods and variation amplitudes in the range of
and
, determined from the investigated data.
Eight Exoplanet Candidates in SAO Survey Yakovlev, O. Ya; Valeev, A. F.; Valyavin, G. G. ...
Astrophysical bulletin,
03/2023, Letnik:
78, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We report eight new exoplanet candidates discovered at the Special Astrophysical Observatory of the Russian Academy of Sciences using the transit technique. Photometric observations were performed ...with a 50-cm robotic telescope during the second half of 2020. Transits with depths of
and periods
were detected in
–
stars. All the stars considered are dwarfs with radii
(with an uncertainty of up to
for a single star). We use simulations to estimate the candidate radii (all are greater than 1.4 times the Jovian radius), semi-major axes of their orbits (0.012–0.035 AU), and other orbital parameters. We report the transit light curves for two stars obtained in 2022 based on individual observations.
We present the results of the first year of searching for polar candidates within the 3BS (3-Band Survey) program using medium-band filters. Observational data for 84 selected objects from the ...catalog of cataclysmic variables of the CRTS DR1 sky survey were obtained while implementing the program. A dwarf nova during its outburst and a polar were detected. The available archival data are analyzed. The dwarf nova is of the U Gem or Z Cam type and contains a massive secondary component with
. For the polar found we have estimated the orbital period
and calculated the magnetic field strength of the white dwarf
MG.
We used the 0.5-m robotic telescope located at the Special Astrophysical Observatory of the Russian Academy of Sciences for monitoring two square degrees of the sky with the aim of detecting new ...exoplanets. A dimming of the visible brightness is expected due to the exoplanets transiting their host stars. We analyzed about 25,000 raw images of stars taken in the period between August 2020 and January 2021 and plotted the light curves for about 30,000 stars on a half-year timescale. Five newly discovered exoplanet candidates are being investigated to determine their transit event parameters. We also present the light curves for dozens of binary stars.
We present a catalog of 150 variable stars, including 13 stars with exoplanet candidates. 37 stars were identified as variables for the first time. As a result of a 2.5-year photometric survey of ...exoplanets, we have obtained and analyzed light curves for almost 50 thousand stars in fields around white dwarfs WD 0009+501 and GRW +708247. Here we describe observations and data processing, the search for variable stars, their cross-identification with other catalogs and classification. The catalog is published in open access and contains the primary classification of variability, light curves and their parameters.
Here we present eight new candidates for exoplanets detected by the transit method at the Special Astrophysical Observatory of the Russian Academy of Sciences. Photometric observations were performed ...with a 50-cm robotic telescope during the second half of 2020. We detected transits with depths of \(\Delta m = 0.056-0.173^m\) and periods \(P = 18.8^h-8.3^d\) in the light curves of stars with magnitudes of \(m = 14.3-18.8^m\). All considered stars are classified as dwarfs with radii of \(R_* = 0.4-0.6 R_{sun}\) (with the uncertainty for one star up to \(1.1 R_{sun}\)). We estimated the candidate radii (all are greater than 1.4 times the Jovian radius), semi-major axes of their orbits (\(0.012-0.035 AU\)), and other orbital parameters by modelling. We report the light curves with transits for two stars obtained in 2022 based on individual observations.
We used the 0.5-m robotic telescopes located at the Special Astrophysical Observatory of the Russian Academy of Sciences for monitoring two square degrees of the sky with the aim of detecting new ...exoplanets. A dimming of the visible brightness is expected due to the exoplanets transiting their host stars. We analyzed about 25000 raw images of stars taken in the period between August 2020 and January 2021 and plotted the light curves for about 30000 stars on a half-year timescale. Five newly discovered exoplanet candidates are being investigated to determine their transit event parameters. We also present the light curves for dozens of binary stars.
