Radio observation of XTE J1810-189 with MeerKAT during its October 2026 outburst

ATel #18119; Souvik Manik (Indian Institute of Technology Kanpur), Sabyasachi Pal (Midnapore City College), Manoj Mandal (Physical Research Laboratory), Sachindra Naik (Physical Research Laboratory), Jaya Chowdhury (Physical Research Laboratory), Andrea Sanna (Università degli Studi di Cagliari), Gaurava K. Jaisawal (DTU Space)
on 25 Oct 2026; 17:54 UT
Credential Certification: Manoj Mandal (manojmandal@prl.res.in)

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The neutron star low-mass X-ray binary XTE J1810-189 was discovered during its 2008 outburst (Markwardt et al, ATel #1424), and its position was subsequently refined using Chandra observations (Chakrabarty et al. 2008, ATel #1490). Recently, MAXI/GSC reported renewed X-ray activity from the source in September 2026 (Negoro et al., ATel #18101). We subsequently conducted coordinated observations with NuSTAR and the Neil Gehrels Swift Observatory/XRT to investigate its X-ray properties. Follow-up observations revealed a thermonuclear X-ray burst (Mandal et al., ATel #18115).

Radio observations with the Karl G. Jansky Very Large Array (VLA) on 2026 October 21 detected the source at 10 GHz with a flux density of 87.3 ± 6.7 μJy (Pattie et al., ATel #18117). Pattie et al. conducted the observation in an almost entirely C-configuration setup, with a maximum baseline of about 3 km.

We also observed XTE J1810-189 with MeerKAT on 2026 October 19, two days before the VLA observation reported in ATel #18117. We observed XTE J1810-189 in L-band (856-1712 MHz; central frequency = 1.28 GHz) for approximately 1.32 hours (4.73 ks), including about 1 hour of on-source exposure with a maximum baseline of approximately 7.23 km. The observation commenced on 2026 October 19 at 16:56:13.462 UTC (MJD 61332.70571). We performed standard interferometric calibration using PKS B1934-638 as the primary flux-density and bandpass calibrator and J1833-2103 as the complex-gain calibrator. We observed MeerKAT simultaneously with NuSTAR (ATel #18115).

Our MeerKAT image reveals that XTE J1810-189 is located in a complex radio field containing several supernova remnants, HII regions, and extended filamentary emission distributed across the imaged field of view. We detected a radio source at RA = 18h10m20.90s, Dec = −19^°04^′14.19^′′. The source is offset by approximately 3.0^′′ from the Chandra position of XTE J1810-189 (RA = 18h10m20.86s, Dec = −19^°04^′11.2^′′; ATel #1490) and 2.6^′′ from the VLA-reported nominal radio position (RA = 18h10m20.85s, Dec = −19^°04^′11.64^′′; ATel #18117). The synthesized beam corresponding to the image is 6.11′′ × 5.65′′. The Chandra and VLA locations of the source are within the measured synthesized beam. The positional proximity suggests a possible association with XTE J1810-189, although further astrometric validation is required to establish the identification. The source has a measured flux density of approximately 123 μJy at 1280 MHz, and the image has an RMS noise level of approximately 15 μJy beam^-1. These measurements provide an additional radio-frequency view of the source during its ongoing outburst. Further analysis will be used to characterize its radio emission and investigate its connection with the accretion activity.

We thank the staff of the South African Radio Astronomy Observatory (SARAO) for facilitating these observations. MeerKAT is operated by SARAO, a facility of the National Research Foundation of South Africa.