New radio detection of MAXI J1820+070 with MeerKAT

ATel #15277; Francesco Carotenuto (Universite de Paris/CEA-Saclay), Rob Fender (University of Oxford), Patrick Woudt (University of Cape Town), James Miller-Jones (Curtin University), on behalf of the ThunderKAT collaboration
on 14 Mar 2022; 16:52 UT
Credential Certification: Francesco Carotenuto (francesco.carotenuto@cea.fr)

Tweet

After a main outburst in 2018 (Shidatsu et al. 2019, Bright et al. 2020), the last (faint) activity displayed by the black hole X-ray binary MAXI J1820+070 was reported in the X-ray and optical bands between March and April 2021 (ATels #14492, #14495, #14582), and the source has stayed in quiescence since then. In the radio band instead, the last detection of the source dates back to March 2020.

We observed MAXI J1820+070 with MeerKAT as part of the ThunderKAT Large Survey Programme (Fender et al. 2017, arXiv:1711.04132), with the aim of performing periodic follow-up observations of previous targets. MAXI J1820+070 was observed on March 07 2022 for 15 minutes, starting at 06:08 UT (MJD 59645.26). The observation was performed with 60 antennas, at a central frequency of 1.28 GHz (L-band) and with a total bandwidth of 860 MHz.

Interestingly, radio emission is detected at the core position of MAXI J1820+070, with a flux density of 114 ± 10 µJy and a significance of 5 sigma. The emission is consistent with the presence of re-activated compact jets, and it might imply the beginning of a new outburst or reflare. For this reason, we will keep monitoring the source with a weekly cadence, and 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 observations 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 Andrew Hughes in the ThunderKAT collaboration for scheduling the observing blocks and the staff at the South African Radio Astronomy Observatory (SARAO) for their rapid scheduling of 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.