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X Persei - correlation between H-alpha and X-ray variability

ATel #11373; R. Zamanov, K. A. Stoyanov, N. Petrov, Y. Nikolov (Institute of Astronomy and NAO, Bulgarian Academy of Sciences, Bulgaria), D. Marchev (Shumen University, Bulgaria), U. Wolter (Hamburg, Germany)
on 1 Mar 2018; 08:53 UT
Credential Certification: Kiril Stoyanov (kstoyanov@astro.bas.bg)

Subjects: Optical, X-ray, Binary, Neutron Star

We performed H-alpha spectroscopic observations of the Be/X-ray binary X Per, optical counterpart of the slow X-ray pulsar 4U 0352+30, using the 2.0m telescope of the Rozhen National Astronomical Observatory, Bulgaria and the 1.2m TIGRE telescope located in Mexico.

Some of the measured equivalent widths (EW(Ha)) of the H-alpha emission line are:
JD 2457383.34 -33.02Å
JD 2457418.30 -30.28Å
JD 2457654.57 -29.80Å
JD 2457694.54 -33.28Å
JD 2457734.38 -30.88Å
JD 2457830.29 -31.87Å
JD 2458095.22 -24.11Å
JD 2458110.54 -22.35Å
JD 2458120.23 -20.53Å
JD 2458145.22 -18.44Å

Combining the X-rays MAXI data (Matsuoka, M. et al., 2009, PASJ, 61, 999), H-alpha data by Reig et al.(2016, A&A 590, A122) and our data, we find that:
(1) there is a clear similarity between the variability of EW(Ha) and 2-10 keV X-ray flux;
(2) the recent decrease of X-ray flux is accompanied with decrease of EW(Ha) from above 30 Å (March 2017) to 18 Å (February 2018).

On Fig.1 are plotted the EW(Ha) and 2-10 keV X-ray flux (1 day light curve, each 10 observations averaged).

Most probably during the last orbital period the X-ray pulsar severely truncated the outer parts of the circumstellar disc.

Further multiwavelength observations of this source are needed to explore the geometry and the emission processes in this system.

Fig. 1 H-alpha and X-ray variability of X Per