Non-Detection of Radio Emission from Magnetar CXOU J164710.2-455216
ATel #17599; Banshi Lal (NCRA - TIFR), Yash Bhusare (NCRA -TIFR), Ashish Kumar (NCRA-TIFR), Yogesh Maan (NCRA - TIFR), Joeri van Leeuwen (ASTRON)
on 15 Jan 2026; 07:36 UT
Credential Certification: Ajay Kumar (akumar@ncra.tifr.res.in)
Subjects: Radio, Magnetar
After Swift/BAT detected a burst in the direction of the magnetar CXOU J164710.2-455216 on July 26, 2025 (ATel #17312), we had follow-up radio observations using the upgraded Giant Metrewave Radio Telescope (uGMRT) in band-4 (550-750 MHz) and band-5 (1060-1460 MHz). These observations were carried out in phased-array mode on July 31, 2025 (band-4) and August 6, 2025 (band-5). The on-source time was around 80 minutes in each of the bands. The band-4 observation had spectral and temporal resolutions of 48.828 kHz and 655.36 microseconds, respectively, while for the band-5, the values were 97.656 kHz and 81.92 microseconds.
We have searched for periodic emission using DSPSR and PSRCHIVE. We used a period of 10.610644 seconds and made 50-second sub-integrations using DSPSR and then searched over DM and around the period using PSRCHIVE. For single pulses, we used PRESTO first to create dedispersed time series and then search for bright single pulses. Then, we used FETCH to classify the single pulse candidates. We have not detected any periodic or burst emission (single pulse) in our search over the DM range of 100 to 1500 pc cm^-3. The 10-sigma sensitivity limits for periodic emission are 70.8 micro-Jy and 34.2 micro-Jy at band-4 and band-5, respectively, assuming a duty-cycle of 5 percent. For single pulses, the 10-sigma upper limit on fluence is estimated to be 0.13 Jy ms and 0.24 Jy ms, at band-4 and band-5, respectively, assuming a pulse width of 5 ms. We note that the scatter broadening is expected to be 296 ms and 23 ms at band-4 and band-5, respectively, assuming a DM of 500 pc cm^-3, and its effect on the above-mentioned pulse width and duty cycle is taken into account before estimating the upper limits.
Using the simultaneously recorded interferometric data, we could also image the magnetar field at both bands. No significant emission is detected at the location of the magnetar CXOU J164710.2-455216 at either of the two bands. Using these images, we thus place 3-sigma upper limits on radio flux density of the magnetar or an associated magnetar wind nebula to be 594 micro-Jy/beam and 243 micro-Jy/beam at band-4 and band-5, respectively.
We thank the observatory for prompt scheduling of our observations and the GMRT staff for their support. The GMRT is operated by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research.
