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A new hard X-ray transient discovered by INTEGRAL: IGR J17559-2612

ATel #4309; V. Esposito, C. Ferrigno, E. Bozzo (ISDC - University of Geneva, Switzerland), J. Chenevez (DTU Space, Denmark) , S. P. Drave (Univ. of Southampton, UK), M. Del Santo (INAF/IAPS, Italy), K. Watanabe (Florida Gulf Coast University, USA)
on 15 Aug 2012; 20:44 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Carlo Ferrigno (Carlo.Ferrigno@unige.ch)

Subjects: X-ray, Gamma Ray, Request for Observations, Transient

Referred to by ATel #: 4322, 4342

INTEGRAL discovered a new hard X-ray transient, IGR J17559-2612, during the Galactic center observations performed from 2012-08-14 00:02:14 to 2012-08-14 14:45:54 UTC.

The source is detected in the IBIS/ISGRI mosaic at a significance level of 8 σ (observation good time: 50 ks) both in the 20-40 keV and the 40-80 keV energy bands. The corresponding fluxes are 11.9±1.4 mCrab and 17.5±2.1 mCrab (9.2±1.1 × 10-11 and 1.21±0.14 × 10-10 erg/s/cm2, uncertainties are at 68% c.l.).

Due to off-axis pointing, the source is not detected in the combined mosaic of the two JEM-X units with a 3σ upper limits of 15 and 20 mCrab in the 3-10 keV and 10-20 keV energy bands, respectively.

The best source position determined with IBIS is
RA= 268.99 (17h 55m 58s)
Dec= -26.21 (-26d 12' 36")
(J2000) with an associated pointing uncertainty of 3.5 arcmin at 90% c.l. (the Galactic coordinates are l= 3.515 b=-0.572).

The IBIS/ISGRI spectrum can be described (χ2red/d.o.f.=0.4 for 8 d.o.f.) by a power-law (Γ=1.6 ± 0.3, uncertainty at 90% c.l.). The 20-100 keV flux estimated from the spectral fit is 3.0 × 10-10 erg/s/cm2 (18 mCrab).

Multi-wavelength follow-up observations are encouraged to unveil the nature of this transient.