Suppression of cooling by strong magnetic fields in white dwarf stars
We explain the phenomenon of extremely strong magnetic fields being more common in cool (old) white dwarfs than in young ones. As a result of observations of WD1953-011, detailed maps of the surface magnetic-field distribution and brightness/temperature were obtained for the first time. We conclude that strong magnetic fields suppress almost completely the convective transfer of energy from the interiors of these stars to the surface, significantly slowing down their evolutionary cooling. This suppression is what creates the observed excess of strongly magnetic cool (old) white dwarfs relative to the young stars of this type.
(Contact - Valyavin G.G.).
G.Valyavin, D.Shulyak, G.A.Wade, K.Antornyuk and 16 co-authors, 2014, Nature, doi:10.1038/nature13836
Discovery and investigation of the spectral variability of the
high-latitude IR-source IRAS01005+7910
The monitoring of the optical component of the IR source IRAS01005+7910 was carried out during 2000-2013 with the BTA (with a spectral resolution of R=60000). Its spectral variability was discovered for the first time in the BTA spectra. We determined the fundamental parameters (luminosity log L/Lsun=3.6 and effective temperature Teff=21500K) of the central star and the detailed chemical composition of its atmosphere. The presence of forbidden emissions [NII] and [SII] in the spectrum indicates the onset of the ionization of the circumstellar envelope and the nearing planetary nebula stage. We used the positions of stable forbidden emissions to determine for the first time the systemic velocity of the source Vsys=-50.5km/s. The complex pattern of the velocity-field variations is caused by a combination of atmospheric pulsations, variations of the wind geometry and kinematics, and also the possible binarity of the star.
(Contact - Klochkova V.G.).
1. V.G.Klochkova, M.V.Yushkin, A.S.Miroshnichenko, V.E.Panchuk, K.Bjorkman. Discovery of spectral variation in the optical counterpart of IRAS01005+7910. Astron.&Astrophys., 392, 143, 2002.
2. V.G.Klochkova, E.L.Chentsov, V.E.Panchuk, E.G.Sendzikas, M.V.Yushkin. Spectral variability of the IR-source IRAS01005+7910 optical component. Astrophys.Bull., 69, 439, 2014.
Evidence of supercritical accretion in SS433
We have investigated the rapid stochastic variability of SS433 in the X-ray (RXTE) and optical (BTA) ranges and found new evidence for the supercritical regime of accretion onto the black hole in this binary system. We discovered a flat portion (white noise) in the power spectrum of SS433 due to an abrupt increase of the disk thickness in the supercritical region. We prove that at the distances from the black hole greater than the disk spherization radius, the disk is standard, whereas the disk is supercritical at distances smaller than the spherization radius. Both the hard X-ray radiation and the visual light are seen reflected from the walls of the funnel that forms in the wind of the supercritical disk of SS433. The soft X-ray radiation forms in the jets of SS433 and exhibits a 50-second lag, as the jets move with a velocity four times smaller than that of light.
(Contact - Fabrika S.N.).
Atapin K., Fabrika S., Medvedev A., Vinokurov A., X-ray variability of SS 433: effects of the supercritical accretion disc, 2015, MNRAS, 446, 893
Discovery and study of the new polar USNO-A2.0 0825-18396733
Based on the results of observations with the SAO RAS telescopes BTA and Zeiss-1000, we have studied the faint variable star USNO-A2.0 0825-18396733. The system's components orbit the center of mass with a period of P = 0.d08481(2). Their masses are determined as 0.71-0.78M☼ (white dwarf) and 0.18-0.20M☼ (red dwarf). The light of the system was found to be very strongly polarized (the circular polarization reaches 30%). We concluded that a new polar was discovered, i.e., USNO-A2.0 0825-18396733 is an interacting close binary system containing a strongly magnetized white dwarf, the field strength of which exceeds that of the Earth by a factor of tens of millions.
(Contact - Borisov N.V.).
1. Gabdeev M.M., Borisov N.V., Shimansky V.V., Spiridonova O.I., Spectral and Photometric Studies of the Polar USNO-A2.0 0825-18396733, 2015, Astronomy Reports, 59,3, 213-220
2. Afanasiev V.L., Borisov N.V., Gabdeev M.M., Photometric and Polarimetric Observations of a New Polar USNO-A2.0 0825-18396733, 2015, Astrophysical Bulletin, 70, 3, 328-333