A possible radio counterpart of MAXI J1421-613 detected by the ATCA

ATel #5759; M. Coriat (Univ. Cape Town), Tasso Tzioumis (ATNF), S. Corbel (Univ. Paris Diderot & CEA Saclay), R. Fender (Univ. Oxford)
on 14 Jan 2014; 08:17 UT
Credential Certification: Mickael Coriat (mickael@coriat.eu)

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Following the discovery of the new X-ray transient MAXI J1421-613 (ATel #5750, #5751), we conducted a radio observation on 2014 January 11/12 (23:15-01:00 UT) with the Australia Telescope Compact Array in the 1.5B configuration (maximum baseline 4.3 km). We observed at 5.5 GHz and 9 GHz simultaneously and detected a faint radio source at the following coordinates:

RA(J2000) = 14h 21m 37.26s
Dec(J2000) = -61d 36' 25.41"

with the following flux densities:

5.5 GHz: 121 +/- 18 uJy
9 GHz: 144 +/- 27 uJy

which implies a spectral index alpha = 0.4 +/- 0.5 (S = k nu^+alpha). The uncertainties on the position are 0.93 arcsec in both RA and Dec at 9 GHz. This error is quoted at 1 sigma and takes into account the positional uncertainty of the phase calibrator. The source lies 5.3 arcsec from the center of the Swift/XRT error circle (ATel #5751) which has a 2.2 arcsec radius (90% confidence). We are not aware of any catalogued radio source within 1 arc-minute of the ATCA position. Although the XRT and ATCA error circles do not formally overlap, their proximity makes the ATCA source a potential counterpart of MAXI J1421-613. Further observations are planned to test the association.

We thank Phil Edwards for the rapid scheduling of these observations