28 research outputs found
Spectroscopic monitoring of V1357 Cyg = Cyg X-1 in 2002-2004
We discuss the results of optical spectroscopic monitoring of Cyg X-1 = HDE 226868/V1357 Cyg in 2002-2004. Our spectroscopy was carried out at the Terskol Observatory (Kabarda-Balkaria, Russia; the resolving power was R = 45 000 and 13 000) and at the Bohyunsan Optical Astronomy Observatory (BOAO, Korea, R = 30 000 and 44 000). Each spectrum covers most of the optical range. We obtained a total of 75 echelle spectra on 33 nights, during both "soft" and "hard" X-ray states of Cyg X-1. We study the influence of the X-rays on spectral-line profiles using RXTE/ASM X-ray data. We find that the X-ray flare of June 13, 2003 resulted in strong variations of the emission profiles of the Hα and Hellλ4686 Å lines within a night. This behavior is due to variations of the ionization state of the gas in the system. We also analyzed line-profile variations with orbital phase. A spectral atlas of Cyg X-1 was created, and the lines it contains identified. A total of 172 stellar lines and blends belonging to 12 chemical elements (H, He, C, N, O, Ne, Mg, Al, Si, S, Fe, Zn) were identified. The spectral classification of HDE 226868 as an ON star is confirmed. © 2008 Pleiades Publishing, Ltd
Stellar Wind Variations During the X-ray High and Low States of Cygnus X-1
We present results from Hubble Space Telescope UV spectroscopy of the massive
X-ray binary system, HD226868 = Cyg X-1. The spectra were obtained at both
orbital conjunction phases in two separate runs in 2002 and 2003 when the
system was in the X-ray high/soft state. The stellar wind lines suffer large
reductions in strength when the black hole is in the foreground due to the
X-ray ionization of the wind ions. A comparison of HST and archival IUE spectra
shows that similar photoionization effects occur in both the X-ray states. We
constructed model UV wind line profiles assuming that X-ray ionization occurs
everywhere in the wind except the zone where the supergiant blocks the X-ray
flux. The good match between the observed and model profiles indicates that the
wind ionization extends to near to the hemisphere of the supergiant facing the
X-ray source. The H-alpha emission strength is generally lower in the high/soft
state compared to the low/hard state, but the He II 4686 emission is relatively
constant between states. The results suggest that mass transfer in Cyg X-1 is
dominated by a focused wind flow that peaks along the axis joining the stars
and that the stellar wind contribution is shut down by X-ray photoionization
effects. The strong stellar wind from the shadowed side of the supergiant will
stall when Coriolis deflection brings the gas into the region of X-ray
illumination. This stalled gas component may be overtaken by the orbital motion
of the black hole and act to inhibit accretion from the focused wind. The
variations in the strength of the shadow wind component may then lead to
accretion rate changes that ultimately determine the X-ray state.Comment: ApJ, in press, 41 pages, 15 figure
The polarization effects of radiation from magnetized envelopes and extended accretion structures
The results of numerical calculations of linear polarization from magnetized
spherical optically thick and optically thin envelopes are presented. We give
the methods how to distinguish magnetized optically thin envelopes from
optically thick ones using observed spectral distributions of the polarization
degree and the positional angle. The results of numerical calculations are used
for analysis of polarimetric observations of OB and WR stars, X-ray binaries
with black hole candidates (Cyg X-1, SS 433) and supernovae. The developed
method allows to estimate magnetic field strength for the objects mentioned
above.Comment: 18 pages, 6 figure
Results of 40-year Studies of the X-Ray Binary Cyg X-1 = V1357 Cyg
This paper reviews the results of our 40-year studies of Cyg X-1 using various methods and observational data: mainly optical photometric, spectroscopic, and polarimetric ones, with X-ray data also considered. We show that, while performing model calculations approximating observational data, it is vital to take into account a diversity of factors, for example, the accretion structure variations that influence the shape of the orbital light curve. We emphasize the necessity of comprehensive studies, development and usage of all possible methods
Interstellar Matter Structure along the Line of Sight to Cyg X-1
High-resolution spectra (R = 60 000) of Cyg X-1 = V1357 Cyg obtained with the NES echelle spectrograph of the Russian 6 meter telescope (3950–6690 Å) were used to study narrow interstellar absorption lines. We resolved the interstellar line blends by fitting them with Gaussian profiles. The main three absorption components, with the heliocentric radial velocities Vr = −1, −13 and −26 km s−1, were revealed. They correspond to three interstellar gas and dust complexes along the line of sight to the object. Thus, we get information on the distribution of interstellar matter along the way to Cyg X-1. The interstellar calcium abundance and ionization degree, averaged along the line of sight, were determined. A weak component with Vr = −43 km s−1 is revealed in the profiles of the strongest lines. We relate it to the approaching wall of the expanding interstellar envelope around the Cyg OB3 association (superbubble). This finding supports the view that Cyg X-1 was born in this stellar association and is still located in it