ATCA observations of the flaring gamma-ray blazar 4C+01.02

ATel #15377; Philip G. Edwards (CSIRO Space and Astronomy), Jamie Stevens (CSIRO Space and Astronomy), Matthias Kadler (JMU Wuerzburg), and Roopesh Ojha (NASA HQ)
on 12 May 2022; 21:06 UT
Credential Certification: Roopesh Ojha (Roopesh.Ojha@gmail.com)

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Following the report of enhanced gamma-ray activity from a source positionally consistent with the high-redshift (z=2.099, Grasha et al., 2019, ApJS, 245, 3) blazar 4C +01.02 (ATels #14404, #15213, #15274) we have made multi-frequency radio observations with the Australia Telescope Compact Array (ATCA).

Observations of the radio counterpart to 4FGL J0108.6+0134 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), indicate it is at record high levels between 5.5 and 40 GHz. Snapshot observations of several minutes duration were made on 2022 April 14, with flux density calibration provided by PKS B1934-638. Flux densities of 5.6 Jy at 5.5 GHz, 6.4 Jy at 8.5 GHz, 7.0 Jy at 16.7 GHz, and 7.5 Jy at 40 GHz were measured. One-sigma errors in these values are estimated to be 4% for frequencies below 30 GHz, and 11% for frequencies above 30 GHz, which are dominated by systematic effects. Archival ATCA data indicate the radio light curve had a peak around 2011 (~4.6 Jy at 5.5 GHz), and a smaller peak in 2016/17 (~3.7 Jy at 5.5 GHz), with flux densities steadily increasing since early 2020 to their current levels.

The Fermi light curve (https://fermi.gsfc.nasa.gov/FTP/glast/data/lat/catalogs/asp/current/lightcurves/4C+01.02_604800.png) also shows enhanced activity in 2016/17 followed by a small peak in 2021 and a record-high gamma-ray flux at present.

ATCA multi-frequency radio monitoring of this outburst will continue over coming months.

The Australia Telescope Compact Array is part of the Australia Telescope National Facility which is funded by the Australian Government for operation as a National Facility managed by CSIRO. We acknowledge the Gomeroi people as the traditional owners of the Observatory site.