MeerKAT discovery of a variable radio source associated with Swift J1728.9-3613
ATel #12522; Joe Bright (Oxford), Rob Fender (Oxford, UCT), Patrick Woudt (UCT), James Miller-Jones (Curtin)
on 20 Feb 2019; 17:30 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Evangelia Tremou (evangelia.tremou@cea.fr)
Subjects: Radio, Binary, Black Hole, Transient
As part of the ThunderKAT Large Survey Program, we observed the field of Swift J1728.9-3613 with 58 antennas of the MeerKAT radio telescope. The observation was carried out on 2019-01-31 from UT 02:39:47 and lasted for 15 minutes, occurring 6 days after rising X-ray flux from the source was seen with the Swift Burst Alert Telescope (ATel #12436). Data were taken at a central frequency of 1.28 GHz with a bandwidth of 856 MHz over 4096 channels. Calibration and imaging were performed using standard techniques. We detect an unresolved source within the 90% Swift X-ray telescope position region reported in ATel #12445, with an integrated flux density of 11.2 +/- 0.6 mJy. The reported error includes a 5% calibration uncertainty as well as the statistical uncertainty.
We carried out two further observations of Swift J1728 on 2019-02-12 from 02:13:23 (58 antennas) and 2019-02-16 from 03:36:51 (59 antennas), with integration times of 50 mins and 15 mins, respectively. The source is no longer detected in either of these epochs. Due to significant extended structure in the source field, we do not reach the noise level of similar observations made as part of the ThunderKAT program. We set a 3 sigma upper limit of 400 uJy/beam at the location of the source for both of these epochs.
ThunderKAT will run for 5 years and aims to monitor all bright, active, southern hemisphere X-ray binaries in the radio band. For further information on this programme please contact Rob Fender and/or Patrick Woudt.
We thank the staff at the South African Radio Astronomy Observatory (SARAO) for scheduling and carrying out these observations. The MeerKAT telescope is operated by SARAO, which is a facility of the National Research Foundation, an agency of the Department of Science and Technology.
