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Chandra detection of IGR J17498-2921 in quiescence

ATel #3559; Peter G. Jonker (SRON/RU/CfA), Manuel A. P. Torres (SRON/CfA), Danny Steeghs (Warwick/CfA), Deepto Chakrabarty (MIT)
on 14 Aug 2011; 13:20 UT
Credential Certification: P.G. Jonker (pjonker@cfa.harvard.edu)

Subjects: X-ray, Neutron Star, Transient

Referred to by ATel #: 3560, 3561, 3562, 3563, 3568, 3601, 3606, 3622, 3638, 3643

We report on archival Chandra observations of the field containing the currently active accreting millisecond pulsar IGR J17498-2921 (ATels #3351, #3554, #3555, #3558).

The observation consists of a 14.2 ks-long ACIS-I image acquired on 2006 Oct 29 23:41 - Oct 30 04:01 TT as part of the bulge Latitude Survey (Grindlay et al. 2005). The data telemetry mode was set to "very faint" and we reprocessed and analyzed the data using the CIAO 4.1 software developed by the Chandra X-ray Center.

The Chandra image shows a faint 15-count source at R.A.(J2000)=17:49:55.38, 267.48073(6), Dec (J2000)=-29:19:19.7, -29.32214(6) consistent with the Swift position reported by Bozzo et al. (2011, ATel #3358). The number in between brackets in the decimal degrees indicate the localization uncertainty given by the wavdetect tool. This uncertainty does not take the uncertainty in the boresight into account. The positional uncertainty is typically 0.6 arcsec for Chandra.

We associate this source with the quiescent counterpart to the accretion powered msec pulsar IGR J17498-2921. For a fiducial power law spectrum with photon index of 2 and with a value for the Hydrogen column of 3E22 cm-2 (Bozzo et al. ATel #3355) the quiescent 0.5-10 keV flux of this source is 2.5E-14 erg cm-2 s-1. For a typical distance of 8 kpc the source quiescent luminosity 2E32 erg s-1.