First MeerKAT radio detection of the new outburst of Swift J1753.5-0127
ATel #16281; Noa Grollimund (Universite Paris Cite & CEA Saclay), Francesco Carotenuto (Oxford University), Stephane Corbel (Universite Paris Cite & CEA Saclay & Observatoire de Paris), Rob Fender (Oxford University)
on 11 Oct 2023; 14:09 UT
Credential Certification: S. CORBEL (stephane.corbel@cea.fr)
Subjects: Radio, Optical, X-ray, Binary, Black Hole, Transient
The black hole low-mass X-ray binary Swift J1753.5-0127 began a new optical outburst on September 28th when observations with the Las Cumbres Observatory (LCO) network indicated a significant increase in the optical emission (ATel #16262). Swift J1753.5-0127 was then detected in X-rays by Chandra on October 1 and Swift/XRT on October 3 (ATel #16272). Here, we report the MeerKAT radio detection of the new outburst.
Following the optical and X-ray detections, we initiated follow-up radio observations with the MeerKAT radio telescope as part of the X-KAT programme. Observations were carried out at a central frequency of 1.28 GHz, with a total bandwidth of 860 MHz. We used J1939-6342 for flux and bandpass calibration, and J1733-1304 for complex gain calibration. Swift J1753.5-0127 was observed for 15 minutes on 2023 October 1 between 13:07:44.0 - 13:22:39.6 (MJD 60218.552 ± 0.005) and on 2023 October 6 between 14:32:09.1 - 14:47:04.7 (MJD 60223.611 ± 0.005).
On October 1, no source was detected at the location of Swift J1753.5-0127, and we estimated a 3 sigma upper limit of ~ 51 uJy. On October 6, we detected a radio source coincident with the position of the X-ray binary. By fitting a point source in the image plane, we measured a flux density of 0.17 +/- 0.04 mJy (at 1.28 GHz). Radio emission from black hole X-ray binaries originates from relativistic jets (either compact jets or discrete ejecta). In our case, since the source is in the hard X-ray state, we expect this emission to be produced by self-absorbed compact jets.
Multi-wavelength observations are encouraged to study the rise of the outburst. Further radio monitoring is planned, as well as weekly Swift observations of the target.
X-KAT is a large MeerKAT open-time programme to observe X-ray binaries in the radio band, performing weekly monitoring of bright, active systems, with capacity for higher cadence observations, and in coordination with large X-ray and optical monitoring programmes. For further information on this programme contact Rob Fender. The Swift follow-up of X-ray binaries is largely performed as part of the SwiftKAT program, which provides quasi simultaneous X-ray coverage of the X-KAT targets.