A state change of H1743-322 confirmed by INTEGRAL observations
ATel #1808; L. Prat, J. Rodriguez (CEA, France), M. Cadolle Bel, E. Kuulkers (ESAC, Spain), J. A. Tomsick (SSL Berkeley, USA), S. Corbel, M. Coriat (CEA & Univ. Paris 7, France), A. Goldwurm (CEA & APC, France), J. Wilms (ECAP, Germany)
on 24 Oct 2008; 08:41 UT
Credential Certification: Jerome Rodriguez (firstname.lastname@example.org)
Subjects: X-ray, Gamma Ray, Binary, Black Hole, Neutron Star, Transient
Referred to by ATel #: 1829
The last INTEGRAL observations from the Galactic Center (GC) and Galactic Bulge (GB) programs
confirm the state transition undergone by H1743-322 into a softer state (Atel #1804).
Since its renewed activity spotted on UT 2008 Sep 23 (See Atel #1739
), H1743-322 was followed
every ~2 days by INTEGRAL as part of these two programs (Atel #1745
), and as part of ToO
observations (Atel #1779
). Since the onset on the outburst, the ISGRI spectra can be well
fitted by a power-law with a high-energy cutoff (reduced chi-squared between 0.8 and 1.5 depending on
the observation). Between Sep 23 and Oct 19, the source stayed in a Low-Hard State (LHS) with
spectral indexes in the range 1.4--1.7. The 20-200 keV flux, after a quick initial increase, slowly
decayed from 4.54 e-9 erg/cm2/s at the apex on Oct 4 to 3.53 e-9 erg/cm2/s on Oct 16.
However, the last 3 observations showed drastic changes in the spectral characteristics of the
On Oct 19, during a 12.6 ks GB observation, the photon index was 1.84 (Â±0.05), and the 20-200
keV flux was 3.03 e-9 erg/cm2/s.
On Oct 21, during a 42 ks GC observation, the photon index increased to 2.3 (Â±0.1), while the 20-200
keV flux dropped to 1.67 e-9 erg/cm2/s. This transition was further confirmed by the third
observation that occurred on Oct 22, during a 12.6 ks GB observation. The
photon index was then 2.2 (Â±0.1), and the 20-200 keV flux was 1.75 e-9 erg/cm2/s. Therefore, the 20-200 keV flux decreased by ~45% within two days and, at the same time, a softening of the spectra occurred.
RXTE observations made on 2008 October 23 03:18-04:39 UT (Atel #1804
) allowed the identification of
this new spectral state with a Hard-Intermediate State (HIMS). Our INTEGRAL observations therefore
confirm the state transition of H 1743-322. In addition, the monitoring of this source allows us to
locate the time of the transition between 2008 Oct 19 and Oct 21, hence at least two days before the
RXTE observations. The rapid evolution in the hard X-ray range may indicate an acceleration of the
source evolution, probably towards softer states.
We'll continue the monitoring of the source through GC and GB, as soon as new observations will be
scheduled. Further multiwavelength observations are strongly encouraged.