Outburst from EXO 2030+375
ATel #843; R. H.D. Corbet (GSFC/USRA) and A. M. Levine (MIT), for the RXTE ASM team at MIT and NASA/GSFC
on 23 Jun 2006; 20:40 UT
Credential Certification: Robin Corbet (corbet@gsfc.nasa.gov)
Subjects: X-ray, Binary, Neutron Star, Transient
Observations with the RXTE All-Sky Monitor of the Be/neutron star
binary EXO 2030+375 reveal a recent increase in flux that indicates a
change of source state.
EXO 2030+375 has been seen with the ASM to exhibit regular outbursts
on the known 46 day orbital period since the start of observations
over 10 years ago on MJD 50087. The mean flux at orbital maximum is
1.6 counts/s in the 1.5 to 12 keV range (~20 mCrab) for the entire
mission light curve, and larger peak fluxes of approximately 4
counts/s (~50 mCrab) have been detected during the last few years
(e.g. Wilson et al., 2005, ApJ, 620, 99).
Recent ASM observations show EXO 2030+375 to have been above a flux of
4 counts/s since MJD 53902 and increasing in flux since then. The most
recent observations on MJD 53909 show a mean flux of 13.3 +/- 0.3
counts/s (~180 mCrab).
The discovery observations of EXO 2030+375 with EXOSAT by Parmar et
al. (1989, ApJ, 338, 359) showed peak fluxes comparable to that of the
Crab and the source was in a Type II outburst with no orbital
modulation of the flux. The current increase in flux of EXO 2030+375
may indicate that the source is now starting a Type II outburst. Even
if this not a Type II outburst, the source flux is higher than seen at
any other time with the ASM. Additional observations at X-ray and
other wavelengths are encouraged.
