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Radio observations of the magnetar AX J1846.4-0258

ATel #13950; Mitchell B Mickaliger (University of Manchester), Kaustubh Rajwade (University of Manchester), Benjamin Stappers (University of Manchester), Andrew Lyne (University of Manchester), Lina Levin Preston (University of Manchester)
on 17 Aug 2020; 15:10 UT
Credential Certification: Mitchell Mickaliger (mitchell.mickaliger@manchester.ac.uk)

Subjects: Radio, Magnetar

Referred to by ATel #: 13988

Following the detection of an X-ray flare from the magnetar AX J1846.4-0258 by Swift (ATel #13913) and MAXI/GSC (ATel #13922), we performed follow-up radio observations with the 32-m Mk2 telescope at Jodrell Bank Observatory. We observed the source on 2020-08-05 (MJD 59066) at 17:37:00 UT for 4189 seconds, 2020-08-12 (MJD 59073) at 00:56:33 UT for 2919 seconds, 2020-08-13 (MJD 59074) at 19:40:16 UT for 1969 seconds, and 2020-08-14 (MJD 59075) at 00:39:43 UT for 3330 seconds. These data were recorded using a DFB backend (Manchester et al., 2013), and were coherently dedispersed and folded. All observations were centered at a frequency of 1532 MHz, with a bandwidth of 384 MHz over 32 channels. No detections were made in these four observations. The nominal DM of the source (300 pc cm^-3) agrees with the accepted distance to the source, 5.5--5.9 kpc (Verbiest et al., 2012), based on the NE2001 Galactic free-electron density model (Cordes & Lazio, 2002). Assuming roughly a factor-of-two error on the distance, and using the upper limit from Leahy & Tian (2008) of 13.2 kpc, gives a maximum DM of 1175 pc cm^-3. A further search using 'pdmp,' which is part of the PSRCHIVE software suite (van Straten et al., 2011), was performed around the nominal period (326.6 ms), but did not reveal any radio emission. We then ran a wider search over a DM range of 0--1175 pc cm^-3 and no pulsations were detected. Assuming a duty cycle of 50%, a sky temperature of 10 K, and an effective bandwidth of 250 MHz, the 1-sigma upper limits on the radio flux of this source during these four observations are 86 uJy, 103 uJy, 126 uJy, and 97 uJy, respectively. We plan to continue radio observations of this source.