Increasing radio brightness of XTE J2012+381
ATel #15855; J. C.A. Miller-Jones (Curtin), G. R. Sivakoff (Alberta), D. Altamirano (Southampton), on behalf of the JACPOT-XRB collaboration
on 11 Jan 2023; 03:40 UT
Credential Certification: James Miller-Jones (james.miller-jones@curtin.edu.au)
Subjects: Radio, Request for Observations, Black Hole, Transient
Following the X-ray detection of a new outburst from the black hole candidate X-ray binary XTE J2012+381 (ATel #15826, #15827, #15829, #15844, #15847), we triggered radio observations with the Karl G. Jansky Very Large Array (VLA). We observed on 2022 December 29, December 31, and on 2023 January 5, centered on Modified Julian Dates (MJDs) of 59942.70, 59944.72, and 59949.78, respectively, for approximately 3 minutes on source per epoch. The observations were taken in two 1-GHz basebands, with central frequencies of 5.25 and 7.45 GHz. The radio flux densities increased over the three observations; 5.25 GHz measurements rose from 0.30±0.04 mJy on December 29 to 8.34±0.03 mJy on January 5. The spectrum was slightly steep on all three days, with a spectral index (Sν ∝ να) on January 5 of α=−0.21±0.07. These flux densities and spectral indices appear consistent with rising radio emission from a compact core jet.
The detection of bright radio emission led us to trigger a VLBA and Swift/XRT monitoring campaign for this outburst, with the first VLBA observation taken on 2023 January 9. We strongly encourage further multi-wavelength observations to track the progress of this ongoing outburst, particularly over any state transition that may occur.
We thank NRAO staff for rapidly scheduling these observations.
