INTEGRAL detects an new ouburst from Aql X-1
ATel #280; J. Rodriguez (CEA/SAp, France & ISDC Switzerland), D. C Hannikainen (Obs. of Helsinki), N. Mowlavi (ISDC)
on 18 May 2004; 10:57 UT
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Credential Certification: Jerome Rodriguez (firstname.lastname@example.org)
Subjects: Radio, Millimeter, Sub-Millimeter, Far-Infra-Red, Infra-Red, Optical, Ultra-Violet, X-ray, Gamma Ray, Binary, Black Hole, Neutron Star, Transient, Pulsar
Referred to by ATel #: 286
Further to Maitra et al. (Atel #279), we report on the detection of Aql X-1
in the hard X-rays with the INTEGRAL observatory during observations of GRS 1915+105
performed between May 13 and May 15, 2004. The source is significantly detected
by the ISGRI detector of the IBIS telescope in the 20-60 keV and 60-200 keV energy
ranges at a flux of roughly 110 mCrab in both ranges. Unfortunately Aql X-1 always
lies outside the JEM-X field of view. A study of the RXTE/ASM real time data shows
that Aql X-1 is at a level of about 50 mCrab in the 1.2-12 keV range.
All this suggests that the source is in a hard X-ray state.
Comparison with previous observations (Molkov et al. Atel #259)
shows that the source flux has increased by a factor of at least 3 in
the lower ISGRI energy range.
The long term RXTE/ASM light curve shows, however, that the source returned
to a low activity level after the observations of Molkov et al.,
confirming that it was undergoing a "mini-outburst" event as suggested
by contemporaneous optical observations (Ilovaisky & Chevalier Atel #260).
Our INTEGRAL detection and the source state suggest that Aql X-1 is
entering one of its normal yearly outbursts as suggested by Maitra et al.
Follow-up observations at all wavelengths are strongly encouraged.