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Cygnus X-3 in extreme soft state

ATel #1081; S. Soldi, V. Beckmann, T. J.-L. Courvoisier, I. Kreykenbohm (ISDC)
on 22 May 2007; 17:00 UT
Credential Certification: Volker Beckmann (Volker.Beckmann@obs.unige.ch)

Subjects: X-ray, Binary

Referred to by ATel #: 1092

INTEGRAL observed the Cygnus region 2007-05-21T09:45 until 23:37 UT.
During this observation the HMXB Cyg X-3 was within the field of view of IBIS and JEM-X1 for 9.5 ks. JEM-X1 data show a high state with a flux of (9.4 ± 1.1)E-09 erg/cm**2/sec (551 mCrab) and (0.34 ± 0.08)E-09 erg/cm**2/sec (60 mCrab) in the 3-10 and 10-20 keV energy range, respectively. The spectrum is well represented by a blackbody model with temperature kT = (1.15 ± 0.05) keV. At the same time IBIS/ISGRI shows a flux of only (8.7 ± 1.6)E-11 erg/cm**2/sec (11 mCrab) in the 20 - 40 keV energy band and no significant detection above 40 keV. This extreme soft state appears to be the continuation of a trend observed by Swift/BAT as reported by Krimm et al. (ATEL #1061).

INTEGRAL will observe the Cygnus region again starting on 2007-05-25.

Images and spectra