Quasi-periodic flares in EXO 2030+375 observed with INTEGRAL
  Context: Episodic flaring activity is a common feature of X-ray pulsars in
HMXBs. In some Be/X-ray binaries flares were observed in quiescence or prior to
outbursts. EXO 2030+375 is a Be/X-ray binary showing "normal" outbursts almost
every ~46 days, near periastron passage of the orbital revolution. Some of
these outbursts were occasionally monitored with the INTEGRAL observatory.
Aims: The INTEGRAL data revealed strong quasi-periodic flaring activity during
the rising part of one of the system's outburst. Such activity has previously
been observed in EXO 2030+375 only once, in 1985 with EXOSAT. (Some indications
of single flares have also been observed with other satellites.) Methods: We
present the analysis of the flaring behavior of the source based on INTEGRAL
data and compare it with the flares observed in EXO 2030+375 in 1985. Results:
Based on the observational properties of the flares, we argue that the
instability at the inner edge of the accretion disk is the most probable cause
of the flaring activity.
