ASKAP VAST observations of SPT-SV J222602.8-540533
ATel #17796; Akash Anumarlapudi (UNC-CH), David Kaplan (UWM), Kovi Rose (U. Sydney) and Tara Murphy (U. Sydney), on behalf of the VAST collaboration.
on 12 May 2026; 13:41 UT
Credential Certification: Akash Anumarlapudi (akasha@unc.edu)
Subjects: Radio, Millimeter, Transient, Variables
SPT-SV J222602.8-540533 (ATel #17781) was discovered as a millimeter (mm) transient by the South Pole telescope (SPT) on 2026 April 13 UT. The source exhibited flaring behavior with a inverted spectrum (brighter at 150 GHz than 95 GHz) suggesting that the transient might be self-absorbed at lower frequencies. Here we report the serendepitous 0.9 GHz observations from Variables And Slow Transients Survey (VAST; Murphy et al. 2021) survey, taken at the Australian SKA Pathfinder (ASKAP).
VAST covered the position of this source roughly with a two month cadence over a multi-year baseline. A point source was consistently detected in all the observations (see light curve below), within the error circle of the SPT source. With a flux density of 2 mJy at 0.9 GHz, the radio source appears to be persistent in the VAST data. The latest VAST observation taken on April 13, 2026 at 23:42 UTC, probably just after the discovery of the transient, indicates that the 0.9 GHz light is still dominated by the persistent source. Archival multi frequency ASKAP observations at 1.37 GHz, and 1.7 GHz indicate that the spectrum of the persisent radio source is consistent with being flat (power law index of 0).
VAST will continue to monitor this field with a two-month cadence.
This work uses data obtained from Inyarrimanha Ilgari Bundara / the Murchison Radio-astronomy Observatory. CSIROâs ASKAP radio telescope is part of the Australia Telescope National Facility (https://ror.org/05qajvd42). Operation of ASKAP is funded by the Australian Government with support from the National Collaborative Research Infrastructure Strategy. ASKAP uses the resources of the Pawsey Supercomputing Research Centre. Establishment of ASKAP, Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory and the Pawsey Supercomputing Research Centre are initiatives of the Australian Government, with support from the Government of Western Australia and the Science and Industry Endowment Fund.
VAST light curve for this event can be obtained here
