Aleksandr Tarasov

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We present the results of analyzing Hα spectra of the radio emitting X-ray binary LS I+61 • 303. For the first time, the same 26.5 d radio period is clearly detected in the Hα emission line. Moreover, the equivalent width and the peak separation of the Hα emission line seem also to vary over a time scale of 1600 days. This points towards the ∼ 4 yr(More)
The bright star δ Sco has been considered a typical B0-type object for many years. Spectra of the star published prior to 1990 showed no evidence of emission, but only of short-term line profile variations attributed to nonradial pulsations. Speckle interferometric observations show that δ Sco is a binary system with a highlyeccentric orbit and a period of(More)
We present results from simultaneous multisite high-resolution spectroscopic and photometric observations of f Oph (HD 149757) taken in 1993 May. Our spectroscopic data include about 100 hr of continuous monitoring of the star. The line-proÐle variations of He I j6678, which are characterized by features traveling from blue to red, are well reproduced by(More)
Wavelength selection and tuning of pulsed Ti:sapphire and Nd:YAG lasers is realized, to the best of our knowledge, for the first time by subwavelength surface-relief fused-silica-transmission gratings (SG). High efficiency, high laser damage threshold, and other advantages of these gratings are confirmed by several intracavity laser experiments.
High-resolution Hα monitoring of Cyg X-1, HD226868 was carried out during 1996–2002 and the resultant spectra analysed in conjunction with 1.5–12 keV X-ray monitoring. We demonstrate that the Hα line-profiles have complex variability on different timescales, controlled in particular by the orbital period and the focused wind model of mass loss. We find that(More)
The results of high-resolution spectroscopy of the Herbig Be star HD 200775 obtained within the framework of a cooperative observing programme in 2000–2002 are presented. A new high-activity phase of the object’s Hα line occurred in the middle of 2001 in full agreement with a 3.68-year periodicity predicted by Miroshnichenko et al. (1998). A complicated(More)
By accumulating all available radial velocity data and combining it with our own spectroscopy we present a new and improved ephemeris for Cygnus X-1 (V1357 Cygni/HDE226868). We initially calculate an orbital period of 5.599847±0.000018 days and then, by including the more recent radial velocities of LaSala et al. (1998) and Sowers et al.(1998) we refine(More)
We present high resolution optical spectroscopy and V band photometry obtained during the period 1987–2001 for the Be star X Persei/HD 24534, the counterpart to the X-ray pulsar 4U 0352+30. We find that throughout this interval X Per is highly active, with significant photometric and spectroscopic variability. We identify one episode of complete disc loss(More)
We present the results of our long-term monitoring of BD +53◦2790, the optical counterpart to the X-ray source 4U 2206+54. Unlike previous studies that classify the source as a Be/X-ray binary, we find that its optical and infrared properties differ from those of typical Be stars: the variability of the V/R ratio is not cyclical; there are variations in the(More)
We present 18 years of high resolution and S/N Hα spectroscopy of the Be shell star o And, obtained between 1985–2002. Spectra taken during late 1985 show a pure photospheric profile, with disc re-formation commencing in 1986; a process that is found to occur over long timescales (∼103 days). Analysis of the evolution of the properties of the Hα shell(More)
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