INTEGRAL detection of the symbiotic star RT Cru during a bright hard X-ray state
ATel #3887; V. Sguera (INAF/IASF Bologna Italy), S. P. Drave (Univ. of Southampton, UK), L. Sidoli (INAF/IASF Milano), M. Fiocchi (INAF/IASF Roma), J. L. Sokoloski (Columbia University, USA), A. J. Bird (Univ. of Southampton), A. Bazzano (INAF/IASF Roma), L. Bassani (INAF/IASF Bologna), E. Kuulkers (ESAC/ESA, Spain), A. Malizia (INAF/IASF Bologna), L. Natalucci (INAF/IASF Roma) and A. Tarana (INAF/IASF Roma)
on 25 Jan 2012; 19:30 UT
Credential Certification: Sebastian Drave (firstname.lastname@example.org)
Subjects: X-ray, Gamma Ray, Request for Observations, Binary, Transient, Variables
Referred to by ATel #: 8448
We report the detection with the IBIS/ISGRI telescope on board
INTEGRAL of the hard X-ray emitting symbiotic
star RT Cru (also known as IGR J12349-6434). The source was detected
during the Galactic Plane scan observations
performed between 2012 January 20, 11:26 (UTC) and January 23,
02:34 (UTC). It was inside the field of view of IBIS/ISGRI for
a total on-source time of about 21 ks leading to a detection
significance of 6.2 sigma in the energy band 18-40 keV and
5.9 sigma in the energy band 18-60 keV. A fit to the IBIS/ISGRI
spectrum (18-60 keV) with a power law model resulted
in a good fit (reduced chi_sq = 1.02 for 15 degrees of freedom) with
a photon index of 2.4 (+1.6, -1.4) and a flux of
1.3 x 10E-10 erg cmE-2 sE-1 (18-60 keV). We note that the average
flux of the source in the energy band 18-40 keV (13+/-2 mCrab)
is a factor of 3.4 brighter than that reported in the same energy
band in the 4th IBIS catalog (2.3 Ms exposure).
RT Cru appears to be entered a new bright hard X-ray state like
that observed by INTEGRAL in 2003-2004 (ATel #519).
Following the INTEGRAL detection, we asked for a Swift/XRT follow-up
RT Cru was detected at about 16 sigma level on 24 January 2012 at
18:53:58 (UTC) with a net exposure time of 1978 s.
An absorbed power law model provided an acceptable fit to the
0.2-10 keV spectrum (reduced chi_sq = 0.876 for 9 degrees of freedom)
with a photon index of -0.36 (+0.47, -0.51), an absorption of
NH<1.78 x 10E22 cmE-2 and an unabsorbed flux of
8.2 x 10E-11 erg cmE-2 sE-1 (1-10 keV). There is a possible hint of
an iron line centered at 6.15 (+0.26, -0.14) KeV with EW = 480 eV.
We encourage follow-up observations of this source at all
wavelengths, especially at radio to look for synchrotron emission.