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Swift follow-up observation of IGR J17494-3030

ATel #3989; E. Bozzo, L. Pavan, A. Manousakis, C. Ferrigno, R. Boissay (ISDC, Univ. of Geneva, Switzerland), P. Jonker (SRON/CfA/RU); J. Chenevez (DTU Space, Denmark); V. Grinberg (Dr. Karl Remeis Obs. and ECAP, Germany); I. Caballero (CEA Saclay, France); M. Cadolle-Bel (ESA/ESAC, Spain); L. Kuiper (SRON, NL); A. Paizis, L. Sidoli (INAF/IASF-Milano, Italy); G. Puehlhofer (IAA-Tuebingen, Germany); V. Sguera (INAF/IASF Bologna)
on 21 Mar 2012; 11:08 UT
Credential Certification: E. Bozzo (enrico.bozzo@unige.ch)

Subjects: X-ray, Binary, Black Hole, Neutron Star, Transient

Referred to by ATel #: 4006, 4886

Following the discovery of the new hard X-ray transient IGR J17494-3030 with INTEGRAL (Atel #3984, #3985), a follow-up observation has been performed with Swift on 2012 March 20 at 15:04 UTC (total exposure time 1 ks).

A single object is detected within the JEM-X error circle. The best determined Swift/XRT position (90% c.l.) is at:
(=17h 49m 23.78s, -30° 29' 59.3''; J2000) with an associated uncertainty of 2.2 arcsec (we used the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalog, see http://www.swift.ac.uk/user_objects and Evans et al. 2009, MNRAS, 397, 1177).

The XRT position is consistent with that determined by INTEGRAL/JEM-X (the two positions are 2.9 arcsec apart; see Atel #3984).

The XRT spectrum could be well described (chi^2_red/d.o.f.=0.9/19) with an absorbed power-law model. We estimated an absorption column density of N_H=(2.1+/-0.6)E22 cm^(-2) and a power-law photon index of 2.5+/-0.4 (all uncertainties are at 90% c.l.). The absorbed 1-10 keV X-ray flux is 7.3(-2.0+0.6)E-11 erg/cm^2/s. No significant coherent modulation has been revealed in the XRT data. We estimated a 99% c.l. upper limit of 25% on the pulsed fraction of any sinusoidal modulation with a frequency in the range 0.001-0.2 Hz.
We note that the estimated absorption is larger than the Galactic value expected in the direction of the source, i.e. 0.8E22 cm^(-2).

The XRT position is not consistent with that of the counterpart suggested in the Atel #3986 (the two positions are separated by 1.9 arcmin).
From the same Chandra observation indicated in Atel #3986 (OBID 8767, exposure time 2.1 ks), we noticed that the position of the XRT source falls onto the gaps between two ACIS-I CCDs and thus no meaningful upper limit can be derived on its quiescent X-ray flux.

No obvious optical/IR counterpart was found in the USNO-B1.0 and 2MASS catalogs at the XRT position.

We thank the Swift team for the prompt scheduling of the follow-up observations of IGR J17494-3030.