Interstellar Matter Structure along the Line of Sight to Cyg X-1

Abstract

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.

Keywords

• ism: structure
• ism: interstellar lines
• stars: x-ray binary: cyg x-1
• stars: v1357 cyg
• stars: optical spectroscopy