Explanation of the Origin of Ultraluminous X-Ray Sources
Using optical spectroscopy, we revealed the origin of unusual objects: ultraluminous X-ray sources in other galaxies, which radiate in the X-ray range thousands times stronger than the black holes in our Galaxy. It turned out that these objects are supercritical accretion disks in binary systems with black holes, similar to the supercritical accretor in our Galaxy, SS433, being at the short-term stage of supercritical accretion.
S. Fabrika , A.Vinokurov, O.Sholukhova
S.Fabrika, Y.Ueda, A.Vinokurov, O.Sholukhova, M.Shidatsu, Supercritical Accretion Disks in Ultraluminous X-Ray Sources and SS 433, 2015, Nature Physics, 11, 551
Detection of Considerable Lack of Massive Dwarf Galaxies in the
Local Volume compared to the Standard Cosmology
The sample of about 750 galaxies in the Local Volume (distance smaller than 10 Mpc) gives a unique opportunity to study the properties of galaxies including the faintest objects: the absolute magnitude MB≈-10 and the virial mass Mvir≈109M☼. We have found that the standard ΛCDM model accurately describes the distribution function of galactic circular velocities for massive objects (Vcirc≥70 km/s and Mvir≥5x1010M☼), but five times overestimates the number of dwarf galaxies with circular velocities Vcirc~30-40 km/s. Such a considerable overabundance of predicted large dwarf galaxies with masses Mvir≈1010M☼ in the field causes a complicated problem: to turn out to be lost, these galaxies should be of extremely low surface brightness, with no star formation processes and neutral hydrogen. Up to the present moment, there has been no such a galaxy detected.
I.Karachentsev, D.Makarov, O.Nasonova together with A.Klypin (New Mexico State University)
Klypin A., Karachentsev I., Makarov D., Nasonova O., Abundance of Field Galaxies, 2015, MNRAS, 454, 1798
Detection of Radio Transients and Variable Radio Sources using the Archive
Data of the Cold Surveys
Analyzing the data of four observational periods of the RATAN-600 Cold surveys in 1980-1994 with the calibration curves plotted using the sample of non-variable sources with steep spectra, we detected 73 sources (Slim>20 mJy) with considerable variations of flux density, which are variable according to different statistical criteria, moreover, the variability for 52 of them was determined for the first time; 3 radio transients were also discovered as well as 22 radio sources (4%) not previously mentioned in the RCR catalog. The inference was drawn on the possible use of the observations conducted on RATAN-600 in the survey mode in order to search for faint variable sources and transients and also to study them in detail provided that synchronous multifrequency data is used.
O.Zhelenkova), E.Majorova, A.Temirova
1. E.Majorova, O.Zhelenkova. On the Possibility of Detection of Variable Sources Using the Data of the "Cold" Surveys Carried Out on RATAN-600. Astrophysical Bulletin, Vol.67, Issue 3, pp. 318-339;
2. E.Majorova, O.Zhelenkova. Multiband Study of Radio Sources of the RCR Catalogue with Virtual Observatory Tools. Astrophysical Bulletin, Vol.68, N 4, 371-395 (2013);
3. E.Majorova, O.Zhelenkova, A.Temirova. Search for Variable Sources Using the Data of the "Cold" Surveys in the Right-Ascension Interval 2h≤RA≤6h. Astrophysical Bulletin, Vol.70, N 1, 34-46 (2015);
4. E.Majorova, O.Zhelenkova. Search for Variable Sources Using the Data of the "Cold" Surveys. The 30th conference "Actual Problems of Extragalactic Astronomy", Pushchino, April 8-10, 2013;
5. E.Majorova, O.Zhelenkova. Variable Radio Sources from the "Cold" Surveys Carried Out on RATAN-600. The All-Russian Astronomical Conference "Many-Faced Universe" (VAK- 2013), September 23-27, 2013, Saint Petersburg, p.174;
6. O.Zhelenkova, E.Majorova, A.Temirova. Search for Variable and Transient Sources Using the RATAN-600 Surveys in 1980-1994. "Actual Problems of Extragalactic Astronomy", the 32th conference, Pushchino, April 20-25, 2015, p.19.