Optical spectroscopy of 4U 2206+54 after the enhanced X-ray activity in 2017
ATel #10568; K. Stoyanov, R. Zamanov, A. Borisova (Institute of Astronomy and NAO, Sofia, Bulgaria)
on 11 Jul 2017; 12:15 UT
Credential Certification: Kiril Stoyanov (email@example.com)
We report high-resolution spectroscopy of the High-mass X-ray binary 4U 2206+54 after the recent enhanced X-ray activity of the system detected by INTEGRAL (ATel#10519). The spectra are obtained on 30 June and 7 July 2017 with the ESpeRo spectrograph (Bonev et al. 2017, BlgAJ, 26, 67) mounted on the 2m RCC telescope at Rozhen National Astronomical Observatory, Bulgaria.
We compare the equivalent widths of the H-alpha and H-beta lines with those, measured on spectra
obtained in 2015 and 2016 with the same spectrograph. On the spectra is visible that the equivalent widths of the H-alpha emission line of the spectrum from 30 June 2017 is greater in comparison with the other spectra (see Figure).
This means that the circumstellar disc around the O9.5V donor star is denser than the disc during the other observations. It is possible that the recent X-ray activity is connected with the physical condition of the circumstellar disc since that disc is the main source of material for accretion onto the neutron star.
The measured values of the equivalent width of H-alpha are
-3.50 Å on 24 December 2015,
-2.88 Å on 20 June 2016,
-3.65 Å on 30 June 2017 and
-3.53 Å on 6 July 2017.
H-alpha line profiles of 4U 2206+54