Chandra Localization of Swift J1713.4-4219

ATel #13247; Deepto Chakrabarty (MIT), Peter G. Jonker (SRON), Craig B. Markwardt (NASA/GSFC)
on 31 Oct 2019; 10:32 UT
Credential Certification: Deepto Chakrabarty (deepto@space.mit.edu)

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As part of an ongoing Chandra X-ray Observatory program for precise localization of X-ray transients in low-mass X-ray binaries, we obtained a short Chandra/HRC-I observation of the suspected black hole transient Swift J1713.4-4219 (ATEL #2300), following reports that it was in a new outburst (ATEL #13169, #13226). Our observation was made on 2019 October 30, 06:40 TT (MJD 58786.278), which was 23 days after the new outburst was first detected by INTEGRAL (ATEL #13169). The exposure livetime was 1156.12 s.

The X-ray source was detected with a mean HRC count rate of 0.19(1) count/s. The best-fit X-ray source position is:

RA(J2000) = 17h 13m 40.98s
Dec(J2000) = -42d 18m 38.4s

with an uncertainty radius of 0.6 arcsec (90% confidence). This is consistent with the 2.2 arcsec Swift error circle (ATEL #13226), lying 1.0 arcsec from its center. Our position is also consistent (0.3 arcsec difference) with candidate optical counterpart "A" proposed by Baglio et al. (ATEL #13226). However, it is inconsistent with their candidates "B" and "C", lying 2.2 and 4.6 arcsec away, respectively.

We are unable to measure an energy spectrum with HRC-I. However, if we assume that the absorbed power-law X-ray spectrum measured by Swift on October 23 (ATEL #13226) with Gamma=1.4 and N_H=1.3e22 cm^(-2) has not changed, then our HRC count rate corresponds to an absorbed (unabsorbed) X-ray flux of 2.0e-11 (3.0e-11) erg/cm^2/s in the 0.2-10 keV band.