Publications
Section: PZ: main journal
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In the course of our work on the 80th Name-List of Variable Stars, we encountered a field in Pegasus with about 70 variable stars announced as new discoveries from the WASP0 survey. Our analysis shows that the amount of wrong information published for these stars is unacceptably large. We present correct information on WASP0 variables, both those that still remain unstudied by other authors and those with reliable studies in the literature. Our new information is based on publicly available sky surveys. We also discuss requirements to presentation of data on new variable stars that permit to include information into variable-star catalogs without a too large amount of extra work for catalog compilers.
We report on our photometric analysis of the poorly studied cataclysmic variable in Ophiuchus, 1RXS J174320.1-042953 (DDE 11). The results of the monitoring with the Bradford Robotic Telescope (BRT) are presented, as well as the time-resolved photometry obtained at the Montecatini Astronomical Centre. The long-term behavior of J1743-0429 shows that it is a probable magnetic cataclysmic variable (polar), with a large difference between its low and high states. The orbital period obtained from our observations is 0.0866 d, or 2.08 h, close to the lower boundary of the period gap of cataclysmic variables.
On 2012 April 25, we acquired spectra and images of NGC 5775 OT PSN J14535395+0334049, classified as a calcium transient similar to NGC 300 OT and SN 2008S in NGC 6496. The Russian 6-m telescope and the SCORPIO focal reducer were used. The spectral range was 4070 - 5830 A and the spectral resolution, 5.4 A. The spectrum is noisy and shows a continuum with an H_{beta} emission line. The line has a two-component profile containing a narrow component, with FWHM ~ 300 km/s, and a broad one, with FWHM ~ 4000 km/s. The object is located at the front of the edge-on galaxy disk, it is weakly reddened. We estimate its M_V as -13.7m on the date of observation, typical of a calcium-type supernova impostor.
Photometric CCD observations of the pre-main-sequence Herbig Ae star WW Vul on separate nights during 2007-2011 are presented. The star exhibited long-term non-periodic variability in the range of 0.8 mag; rapid variations with a small amplitude were superimposed. The results of a search for periodicity in the light variations are reported.
We have recovered the "lost" variable star NSV 08092 = HV 8988. Form archive data, its brightness variations are rather unusual. In some aspects, it resembles R CrB stars, but it can be an analog of the famous unusual post-AGB star FG Sge.
After 33 years of extensive studies of SS 433, we have learnt much about this unique system with moving emission lines in the spectrum. The orbital inclination is known from spectroscopic observations of moving lines; the distance is derived from radio interferometry of relativistic jets; the mass ratio of its components is determined from X-ray observations of jets' eclipses. In 2005, the accretion donor was detected as an A4-A8 giant, and its contribution to eclipse light was measured spectroscopically. In the present paper, the A-type star was detected via multicolor photometry on the basis of its Balmer jump. A method is proposed to estimate the interstellar reddening, able to measure the individual law of interstellar absorption for SS 433 from spectrophotometry. The method is based on extracting the energy distribution of the spectral component of a very hot source covered in eclipse and on the comparison of its energy distribution to the Planck energy distribution of a black body with the temperature exceeding one million K. The determination of general parameters of SS 433 leads to fairly accurate estimates of luminosity, radius, and mass of the A star in the system, and consequently leads to an accurate estimate of the mass of the compact component, the source of jets. The latter mass is between 1.25 and 1.87 solar masses. The reasons for overestimating this mass when using the dynamical method are discussed. In our opinion, the presence of a black hole in this system is excluded.
Working on identifications of objects from the NSV catalog, we found that NSV 07212 and NSV 07329 were two probable variables of the rare RCB type. Both stars enter the ASAS-3 variable-star catalog as "MISC" variables (i.e. those lacking a reliable variable-star classification), with spurious periods. We present the results we obtained for the two variables, mainly from our analysis of the ASAS-3 photometry. NSV 07212, a known carbon star, is a variable with an amplitude as large as 7m. Though, in this case, the RCB classification is rather certain, spectroscopy of both stars is needed.
I report on the discovery of two cataclysmic variables in the same field in Lyra, originally identified on the base of their magnitudes in the USNO-B1.0 catalog and on Palomar images. The historical light curves were analyzed from 300+ photographic plates of the Moscow collection, covering 35 years of observations. One of the two stars, USNO-B1.0 1320-0390658, is showing rather frequent outbursts from B~20 to B=15.2 and is likely a dwarf nova of the UGSS subtype. The other variable, USNO-B1.0 1321-0397655, with only one observed outburst in 1993, from R~19 to I=11.8, is either an UGWZ dwarf nova or a recurrent nova. In both cases, its next outburst can occur in the nearest future.
New GCVS names are announced for several young variable stars of special astrophysical interest. These stars will enter the 80th Name List of Variable Stars but are given GCVS names now in order to make it possible for investigators to use permanent names in their publications.
An initial investigation of two poorly studied eclipsing binaries separated by about 3' in the sky is presented. The first star (GSC 2576-01248) was discovered by the TrES exoplanet search project. The second one (GSC 2576-02071) was identified by the authors during CCD observations of GSC 2576-01248. We combine our dedicated CCD photometry with the archival TrES observations and data from the digitized photographic plates of the Moscow collection to determine periods of the two variable stars with high precision. For GSC 2576-01248, addition of historical photographic data provides a major improvement in accuracy of period determination. No evidence for period change in these binary systems was found. The lightcurve of GSC 2576-01248 is characterized by a prominent variable O'Connell effect suggesting the presence of a dark starspot and asynchronous rotation of a binary component. GSC 2576-02071 shows a shift of the secondary minimum from the phase 0.5 indicating a significant orbit eccentricity. |
