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One Hundred Years of Observations of the Be Star HDE 245770 (the X-ray Binary A0535+26/V725 Tau): The End of an Active Phase ?
UBV observations of the X-ray binary system A0535+26/V725 Tau at theCrimean Station of the Sternberg Astronomical Institute in 1980-1998 arepresented. Based on our and published data, we analyze the photometrichistory of the star from 1898. Over a period of 100 years, the starapparently showed all three activity phases (B, Be, Be-shell) of Bestars. We conclude that the X-ray activity of the object is attributableto the 1970-1997 outburst of the Be star due to envelope ejection. Thestar's colors during the minimum light of 1998 and its 1953-1956 colors(before the outburst) correspond to the spectral type B0-B1 at the colorexcesses E_{B-V} = 0.74 and E_{U-B} = 0.48, in agreement with thecurrent spectral type O9.7. The minimum light of 1998 and the colorexcesses are used to determine the colors of the additional radiation,analyze their evolution during the 1973-1997 outburst, and refine thedistance to the object (3 kpc). The colors of the additional radiationat maximum light of the star (1973-1980) match the colors of a hydrogenplasma with T_e = 1.5 x 10^4 K which is optically thick in the Balmercontinuum. The brightness decline corresponds to a decrease in theoptical depth of the plasma; at V = 9.1 mag, it becomes optically thinin the Balmer continuum with T_e = 10^4 K and N_e = 1010 -1012 cm^{-3}. This conclusion is consistent with the model ofa circumstellar envelope but is inconsistent with the existence of anaccretion disk around the neutron star. All the additional radiationresponsible for the optical variability is produced by a single source.The intensity of the H_alpha emission line at maximum light (1975-1980)is triple its intensity in 1987-1997, when quasi-periodic lightfluctuations with P = 1400 days were observed. At this time, the lineintensity correlated with brightness. The H_alpha line was in absorptionat the minimum of 1998, and, at present, the star's active phase appearsto have ended.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| Photometric behaviour of the Be X-ray binary A 0535+26/HDE 245770.
The photometric behaviour of HDE 245770 is discussed and new photometricresults are given in this paper. By collecting the published photometricdata of the last ten years, a long history of the photometric behaviourof the star has been constructed and the secular variation time scales,506d and 755d, have been estimated. One-armed disk oscillation model isused to explain the periodicity. Some observing facts are used to checkthe new theory of equatorial disk formation.
| On the Optical Variability of a Be Star, HDE 245770 - The Optical Counterpart of the Transient X-Ray Pulsar A0535+26
Not Available
| A 0535 + 26/HDE 245770 - A typical X-ray/Be system
A review of the principal characteristics and behavior of the X-ray/Besystem A 0535 + 26/HDE 245770, emphasizing the morphological andphysical aspects, is presented. The binary system is formed by aO9.7IIIe star that acts as a 'normal' Be star and by a neutron star,which is a slow X-ray pulsar (104s). Based on the behavior of the binarysystem, derived mainly from simultaneous multifrequency measurementsshowing differences in intensity of the X-ray outbursts and inrepetition time and activity of the Be star, three types of X-rayoutbursts related to the variable activity of the Be star areestablished.
| Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986)
This paper presents the catalog of photometric data in the Stromgrensystem obtained during the first four years (October 1982 - September1986) of the Long-Term Photometry of Variables (LTPV) program at ESO.The data are available in computer-readable form.
| 558 peculiar stars discovered at Abastumani
A list of 558 peculiar stars is given: 208 Ap stars, 342 Am stars, sevenobjects with composite spectra, and one Ba II star. All were discoveredat Abastumani Astrophysical Observatory in the course of classifyingstars in the galactic anticenter direction.
| An optical study of the Be/X-ray transient HDE245770/A0535 + 26
New spectroscopic data and IR and optical photometry of the Be starHDE245770, the optical counterpart of the transient X-ray source A0535 +26, are presented. The radial velocity measurements are used togetherwith published data and a recently proposed X-ray orbital solution toconstrain the geometry of the binary system. A classical Be envelope oflow expansion velocity is assumed, and the possible densities, velocitylaws, and structures of the envelope compatible with the observed IRexcess and X-ray flux at periastron and apoastron are discussed.
| Simultaneous ultraviolet and optical observations of HDE 245770/A 0535+26
High and low dispersion UV spectra of HDE 245770, which is the opticalcounterpart of the recurrent transient X-ray pulsar A 0535+26 wereobtained. UVB photometric measurements were simultaneously carried outand some medium dispersion optical spectra obtained close to the UVones. A preliminary analysis of the UV spectra is given.
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Наблюдательные данные и астрометрия
| Созвездие: | Телец |
| Прямое восхождение: | 05h37m39.86s |
| Склонение: | +26°13'02.8" |
| Видимая звёздная величина: | 7.934 |
| Собственное движение RA: | 9.7 |
| Собственное движение Dec: | -13.2 |
| B-T magnitude: | 8.308 |
| V-T magnitude: | 7.965 |
Каталоги и обозначения:
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