Radio detection of XTE J1810-189 during its ongoing outburst with the Very Large Array
ATel #18117; Eliot Pattie (Univ. of Amsterdam), Nathalie Degenaar (Univ. of Amsterdam), Unnati Kashyap (Texas Tech Univ.), Jacob van den Eijnden (Univ. of Amsterdam), Thomas Maccarone (Texas Tech Univ.)
on 23 Oct 2026; 13:30 UT
Credential Certification: Eliot Pattie (e.c.pattie@uva.nl)
Subjects: Radio, Binary, Neutron Star, Transient
The neutron star low-mass X-ray binary XTE J1810-189 recently went into outburst on September 12, 2026 (ATel #18101, #18115). We triggered a Very Large Array (VLA) program for a 1 hour observation beginning on UTC 2026-10-21 23:38:22 (MJD 61334.983) to determine its radio flux density. The VLA observation was performed at X band (8-12 GHz) in an almost fully C configuration for a maximum baseline of 3 km. Standard continuum calibration was performed with 3C286 as the flux density and bandpass calibrator, and J1820-2528 as the complex gain calibrator, with a total of 34.5 minutes of on-source time. XTE J1810-189 was significantly detected at the previously known Chandra position (nominal radio position: 18h 10m 20.855s -19d 04m 11.64s; 2″ angular resolution) with a 10 GHz flux density of 87.3 ± 6.7 μJy. Low surface brightness noise from a nearby supernova remnant was filtered out by restricting the uv range of the data to > 15 klambda. Assuming a distance of 7 kpc, the estimated radio luminosity is 1.6 × 1028 erg/s, and the X-ray luminosity was approximately 3.6 × 1036 erg/s based on MAXI monitoring data at the time of the radio observation. This places XTE J1810-189 as being consistent with many other neutron star low-mass X-ray binaries in the fundamental plane. The spectral index defined as Sν ∝ να using two frequency bands (8-10 and 10-12 GHz) is -0.067 ± 0.867. The outburst is continuing to evolve and further radio follow-up observations are planned with the Very Large Array.
