Confirmation of IGR J17445-2747 infrared counterpart

ATel #10284; Francis Fortin (CEA-Saclay), Sylvain Chaty (CEA-Saclay) and John A. Tomsick (SSL/UCB)
on 18 Apr 2017; 21:59 UT
Credential Certification: John A. Tomsick (

Subjects: Infra-Red, X-ray, Neutron Star, Transient

Referred to by ATel #: 10305

Following the recent detection of the Swift XRT counterpart of IGR J17445-2747 (ATEL #10265) and the updated position computed by Kennea et al. (ATEL #10273), we used images obtained in July 2012 with VLT/ISAAC (P.I. S. Chaty, programme ID 089.D-0181(A)) to constrain the position of the counterpart in near-infrared. We also consider the position reported for the previous XMM Slew counterpart XMMSL1 J174429.4-274609 (Malizia et al. 2010, MNRAS, 408, 975).

The ISAAC images were calibrated using astrometric solution with 2MASS sources. Our observations are deeper than 2MASS, and we find that only 2MASS J17443041-2746004 is consistent with all the X-ray positions obtained from the three aforementioned observations. It is located at position RA/Dec (J2000) = 266.126718, -27.766800, equivalent to: RA(J2000) : 17h 44m 30.412s Dec(J2000) : -27d 46m 00.48s, with a position error of 0.5 arc-seconds radius (90% confidence). The ISAAC image with all the error circles superimposed are reported in the finding chart (see link).

We confirm this source is associated with the bright K=9.6 2MASS J17443041-2746004 object, which is the likely counterpart of the X-ray source as suggested by Kennea et al. (ATEL #10273). However, Heinke et al. (ATel #10265) estimate a distance of several kpc for IGR J17445-2747, which would be very unusual for an X-ray burster in which the low-mass donor star is as bright as 2MASS J17443041-2746004. We suggest either that IGR J17445-2747 is located much closer, or that it is a very unusual type of X-ray burster.

ISAAC near-IR image with X-ray error circles