Continued monitoring of PMN J1603-4904 with MeerKAT and H.E.S.S.
ATel #17307; G. Bruni (INAF-IAPS), M. Brienza, G. Migliori, M. Giroletti, E. Liuzzo (INAF-IRA), E. Bronzini (U. Bologna & INAF-OAS), M. Kadler (U. Wuerzburg), L. Hernandez-Garcia (U. Valparaiso), F. Panessa, J. Rodi (INAF-IAPS), E. Torresi, P. Da Vela (INAF-OAS), M. Cerruti (U. Paris Cite), , C. Reynolds (CSIRO), and S. J. Wagner (U. Heidelberg), for the H. E. S. S. collaboration
on 25 Jul 2025; 09:36 UT
Credential Certification: Gabriele Bruni (gabriele.bruni@inaf.it)
Subjects: Radio, VHE, AGN
On June 26, 2025, we conducted the second epoch of our MeerKAT monitoring of PMN J1603-4904. The observation was coordinated with the H.E.S.S. team, who observed the target on the same day. The results are presented below.
As in the first epoch, MeerKAT observed the target for approximately 15 minutes at 3 GHz (S4 band). Phase referencing was applied, and the data were processed using the SARAO Science Data Processor (SDP) continuum pipeline. The final image has an angular resolution of 4.66" x 4.29" with a position angle of 77.1 deg, and an RMS noise level of 40 uJy/beam. The measured flux density is 1.43+/-0.07 Jy, taken 33 days after the initial H.E.S.S. detection (ATel #17205) and 12 days after the first MeerKAT epoch (ATel #17239). This value is consistent, within uncertainties, with the previous measurement, indicating no significant radio variability to date.
The High Energy Stereoscopic System (H.E.S.S.) conducted follow-up observations of the source in very-high-energy (VHE; E > 100 GeV) gamma rays during the night of 26-27 June 2025, 26 days after the conclusion of the initial ToO campaign on 31 May. Offline analysis of the data from this night indicates that the source remains active in VHE, with a total detection significance of 9 sigma achieved over 1.9 hours of observation, and exceeding 4 sigma per run. The measured flux is comparable to the levels reported during the initial ToO observations (see ATel #17205).
Further MeerKAT and H.E.S.S. observations with a monthly cadence may follow and will be reported here if conducted.
The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation.
H.E.S.S. is an array of five imaging atmospheric Cherenkov telescopes to study very-high-energy gamma-ray sources and is located in the Khomas Highlands in Namibia. It was constructed and is operated by researchers from Armenia, Australia, Austria, Denmark, France, Germany, Ireland, Japan, the Netherlands, Poland, South Africa, the UK, and the host country, Namibia.
