MeerKAT radio non-detection of the X-ray transient MAXI J1609-487
ATel #18144; P. Aggarwal (University of Oxford), A. K. Hughes (University of Oxford), R. Fender (University of Oxford and University of Cape Town), S. Motta (INAF-OAB), N. Grollimund (Universite Paris Cite), on behalf of the X-KAT collaboration
on 6 Nov 2026; 18:17 UT
Credential Certification: Andrew Hughes (hughesakh@gmail.com)
ATel #18123 reported the discovery of the X-ray transient MAXI J1609-487 on 28 October 2026. Subsequent X-ray rebrightening on 31 October was reported in ATel #18136, with the X-ray properties suggesting a possible Galactic transient origin, although the authors acknowledge that the rise may be due to incomplete background subtraction and detector contamination. We obtained follow-up radio observations of the field with the MeerKAT telescope as part of the X-KAT programme.
The field of MAXI J1609-487 was observed with MeerKAT on 31 October 2026, starting at 10:21:53 UTC, for 10 min. Observations were conducted at L-band with a central frequency of 1.28 GHz and a nominal bandwidth of 856 MHz. J1939-6342 was used for bandpass calibration and to set the absolute flux scale, whereas J1726-5529 was used for complex-gain calibration. The resulting images had a root-mean-square noise of approximately 30 uJy/beam and a restoring beam of approximately 9 x 5 arcsec (position angle 143 deg).
We compared our observation with archival MeerKAT L-band observations from 2021 and a stacked RACS-mid (1.37 GHz) image constructed from four separate pointings. Cross-matching the archival and recent images revealed no new radio sources (detectable above the noise levels of the comparison images) within the approximate 0.2 deg X-ray localisation region (including statistical and systematic uncertainties). Our observations reached noise levels a factor of 2-3 lower than the archival images, limiting any new radio source to a flux density of approximately 200 uJy or less. We plan to obtain further radio observations over the coming weeks to search for a delayed radio brightening and encourage continued multi-wavelength follow-up.
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.
