MeerKAT and ATCA detection of MAXI J1348-630
ATel #14029; Francesco Carotenuto, Stephane Corbel (CEA-Saclay), Evangelia Tremou (LESIA, CNRS), Rob Fender (Oxford, UCT), Patrick Woudt (UCT), James Miller-Jones (ICRAR/Curtin), on behalf of the ThunderKAT collaboration, and Pikky Atri (ICRAR/Curtin)
on 18 Sep 2020; 13:09 UT
Credential Certification: S. CORBEL (stephane.corbel@cea.fr)
Subjects: Radio, Black Hole, Transient
The occurrence of a new mini-outburst of the black hole candidate MAXI J1348-630 has been reported in the X-rays by MAXI/GSC on MJD 59098 (September 5 2020, ATel #13994), and in optical by LCO on MJD 59104 (September 12 2020, ATel #14016). This is the 6th source re-brightening occurred after the major outburst (see ATel #13994 for details). Optical observations performed on September 14 2020 (MJD 59106) suggest that the mini-outburst has already entered in a decay phase (ATel #14016).
We have been monitoring the source since the start of the discovery outburst in January 2019 with the MeerKAT radio-interferometer (ATel #12497, ATel #13467), as part of the ThunderKAT Large Survey Programme (Fender et al. 2017, arXiv:1711.04132). The monitoring had a regular weekly cadence during the major outburst, and follow-up observations were triggered for each of the reported mini-outbursts.
Following the recent alerts, we observed MAXI J1348-630 on September 12 2020 (MJD 59104.701) for 15 minutes, starting at 16:49 UT. The observation was performed with 60 antennas, at a central frequency of 1.28 GHz and with a total bandwidth of 860 MHz. MAXI J1348-630 is detected at a flux density of 0.52 ± 0.03 mJy and at the known core position.
We also observed MAXI J1348-630 on September 12th with the Australia Telescope Compact Array (ATCA), from 04:07-06:46 UT (MJD 59104.23 ± 0.06), under project code C2538. We observed in the 4cm band, in two spectral windows of 2 GHz, centred at 5.5 and 9.0 GHz. The array was in its 750B configuration.
We detected MAXI J1348-630 in both bands, with flux densities of 0.56 ± 0.03 mJy at 5.5 GHz and 0.78 ± 0.02 mJy at 9.0 GHz.
Fitting the three flux densities yields a spectral index (α, where Sν ∝ να) of 0.2 ± 0.1, with the caveat that the MeerKAT and ATCA observations are not strictly simultaneous. The value of α implies a slightly inverted radio spectrum, signature of the presence of self-absorbed compact jets. Further multi-wavelength observations are encouraged.
ThunderKAT will run for 5 years and targets X-ray binaries, Cataclysmic Variables, Supernovae and Gamma-Ray Bursts. As part of this programme we perform weekly monitoring observation of 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, and agency of the Department of Science and Innovation.
