Upper limits on the continuum radio emission of SGR J1935+2154 from uGMRT observations
ATel #14395; Mayuresh Surnis (JBCA, University of Manchester), Benjamin Stappers (JBCA, University of Manchester), Fabian Jankowski (JBCA, University of Manchester), Kaustubh Rajwade (JBCA, University of Manchester), Manisha Caleb (JBCA, University of Manchester), Bhal Chandra Joshi (NCRA-TIFR), Manjari Bagchi (IMSc)
on 16 Feb 2021; 18:00 UT
Credential Certification: Mayuresh Surnis ([email protected])
Subjects: Radio, Neutron Star, Supernova Remnant, Transient, Fast Radio Burst, Magnetar
Referred to by ATel #: 14396
Following a series of recent X-ray bursts (GCN #29363, #29373, #29374, #29381, #29425 and ATEL #14359), we observed SGR J1935+2154 with the upgraded Giant Metrewave Radio Telescope (uGMRT) at two epochs. Here we report on the results from the analysis of the interferometric data. These observations were carried out in band-3 (300-500 MHz) on 2020 February 5, 07:00 UT and band-4 (550-750 MHz) on 2020 February 6, 08:15 UT for an on-source time of about 90 minutes. We observed the nearby millisecond pulsar PSR B1937+21 as a test pulsar.
We made radio images of the associated supernova remnant (SNR) G57.2+00.8 at both bands. The synthesized beam size of the band-3 image is about 7.5" x 5.3" with a beam position angle of -84.5 degree while that of the band-4 image is about 5.8" x 3.6" with a beam position angle of 82.2 degree. The SNR images at both the bands are available at the link below. We do not detect any continuum emission at the position of the magnetar with 3-sigma flux density upper limits of 315 microJy and 105 microJy at 400 and 650 MHz, respectively. These limits are more stringent than what we reported during the May 2020 outburst (ATEL #13769, #13777, #13799). An ultra-bright burst like the one detected by The CHIME/FRB Collaboration et al. 2020 (700 kJy ms fluence) would have been detectable in our images, even after averaging over the total observing duration. A recent search for such ultra-bright bursts contemporaneous with X-ray bursts also resulted in a non-detection (ATEL#14382). We are currently analyzing the beamformed, high time-resolution data to search for any periodic emission or relatively fainter single pulses.
We thank the staff of the GMRT who have made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research.
Radio images of SNR G57.2+00.8
