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 (kstoyanov@astro.bas.bg)
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