Upper limits on the radio emission of SGR 1830-0645 from uGMRT observations

ATel #14091; Mayuresh Surnis (JBCA), Bhal Chandra Joshi (NCRA-TIFR), Benjamin Stappers (JBCA), Ketan Sand (Delhi University), Manjari Bagchi (IMSc), Kaustubh Rajwade (JBCA), Fabian Jankowski (JBCA), Manisha Caleb (JBCA), Vishal Gajjar (UCB)
on 13 Oct 2020; 18:31 UT
Credential Certification: Mayuresh Surnis (msurnis@gmail.com)

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Following a recent X-ray burst (Page et al., ATEL #14083) and the subsequent detection of pulsations in the X-ray energy range with a period of 10.4 s (Gogus et al., ATEL #14085; Younes et al., ATEL #14086), we observed SGR 1830-0645 with the upgraded Giant Metrewave Radio Telescope (uGMRT). These observations were carried out in band-4 (550-750 MHz) on 2020 October 11, 18:30 UT for an on-source time of about 45 minutes. We observed the nearby millisecond pulsar PSR B1937+21 as a test pulsar.

We made a radio image of the field with a synthesized beam size of about 7.2" x 4.7" with a beam position angle of 3.4 degree. We do not detect any continuum emission at the position of the magnetar with a 3-sigma flux density upper limit of 300 microJy at 0.65 GHz.

We also carried out periodic and single-pulse searches of the beamformed data resulting in non-detection of any significant radio emission. The 8-sigma upper limit for the fluence of the single-pulse emission assuming a pulse width of 1 ms is 0.21 Jy ms at 0.65 GHz. The 8-sigma upper limit for any periodic pulsed emission assuming a duty cycle of 10% is 42 microJy at 0.65 GHz.

We detected a few strong single-pulses from PSR B1937+21 in the band-4 beamformed data. The radio image of the field is available at the link below.

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 image of the magnetar field