GRB 150101B/Swift J123205.1-105602: Chandra observations

ATel #6893; E. Troja (NASA/GSFC/UMCP), T. Sakamoto (AGU), A. Lien (NASA/GSFC/UMBC), S. B. Cenko (NASA/GSFC), and N. Gehrels (NASA/GSFC)
on 10 Jan 2015; 14:47 UT
Credential Certification: Eleonora Troja (eleonora.troja@nasa.gov)

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We observed the field of the transient Swift J123205.1-105602 (Cummings; GCN 17267) with the Chandra X-ray Observatory beginning on 2015 Jan 09.48 UT (7.83 days post-burst) for a total exposure of 14.9 ks.
At the transient position, we detect two X-ray sources within the Swift/XRT point spread function:

SRCX #1
The first source is located at:

RA(J2000) = 12:32:04.985
Dec(J2000) = -10:56:00.21

with a 90% uncertainty of 0.6 arcsec. This position is consistent with the XRT position (http://www.swift.ac.uk/xrt_positions/00020464/), the bright radio source reported by van der Horst et al. (GCN 17286), and the nucleus of 2MASX J12320498-1056010.
The source is well described by an absorbed power-law with photon index Gamma=2.3 +/- 0.2, and absorption column consistent with the Galactic value of 3E20 cm^-2 (Kalberla et al. 2005). The observed flux in the 0.5-8.0 keV energy band is (4.0 +/- 0.4)E-13 erg cm^-2 s^-1.

SRCX #2
The second, fainter source is located at:

RA(J2000) = 12:32:05.104
Dec(J2000) = -10:56:02.78

with a 90% uncertainty of 0.6 arcsec. This position is consistent with the optical source reported by Fong et al. (GCN 17271).
The source is well described by an absorbed power-law with photon index Gamma=1.8 +/- 0.3, and absorption column consistent with the Galactic value  of 3E20 cm^-2 (Kalberla et al. 2005). The observed flux in the 0.5-8.0 keV energy band is (1.2 +/- 0.2)E-13 erg cm^-2 s^-1.

Both sources do not display significant temporal variability during our observation.

We do not detect any X-ray counterpart at the position of the second radio source reported by van der Horst et al. (GCN 17286) down to a limit of 3E-4 cts s^-1 (95% confidence level).


We thank Belinda Wilkes and the entire Chandra staff for approving and rapidly executing this observation.