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IGR J16393-4643 a possible X-ray counterpart to 3EG J1639-4702 discovered by INTEGRAL

ATel #227; Malizia A., L. Bassani, G. Di Cocco and J. B. Stephen (IASF/CNR Bologna), R. Walter and A. Bodaghee (INTEGRAL Science Data Center) and A. Bazzano (IASF/CNR Roma)
on 30 Jan 2004; 13:06 UT
Credential Certification: Malizia Angela (malizia@bo.iasf.cnr.it)

Subjects: X-ray, Gamma Ray, Black Hole

We report the detection of a source, IGR J16393-4643, at RA (2000)= 16h 39.3m and Dec(2000)= -46o 43' (2 arcmin uncertainty) with the IBIS/ISGRI telescope on board INTEGRAL. The source is detected at ~ 20 sigma level in the 20-100 keV range in a cumulative exposure of the Norma Region ( ~700 ks) with an average flux of approximately 5 x 10^(-11) erg cm^(-2) s^(-1) (about 3 mCrab). Segmentation of the observing period into 4 parts, indicates variability of the source (detection level ranges from 13 sigma in March 2003 to 5 sigma in August/September 2003). Within the ISGRI error box lies AX J1639.0-4642 a bright (approximately 2 x 10^(-11) erg cm^(-2) s^(-1) in the 0.7-10 keV band), flat (photon index=-0.01) and variable ASCA source (Sugizaki et al. 2001, ApJS 134, 77). IGR J16393-4643 lies at ~20 arcmin from the EGRET optically unidentified source 3EG 1639-4702, well within the 95% EGRET error box. After IGR J16316-4028 (Atel #201), IGR J16393-4643 is the second INTEGRAL source likely to be the (hard) X-ray counterpart to an EGRET source. At least four other objects detected by ISGRI fall within the 99.9% EGRET contours, making this part of the sky particularly interesting. Follow-up observations of IGR J16393-4643 and surrounding region are highly encouraged.