Confirmation of pulsed radio emission from Swift J1818.0-1607

ATel #13554; Kaustubh Rajwade (University of Manchester), Benjamin Stappers (University of Manchester), Andrew Lyne (University of Manchester), Mitchell B Mickaliger (University of Manchester), Lina Levin Preston (University of Manchester), Michael Keith (University of Manchester), Patrick Weltevrede (University of Manchester), Michael Kramer (MPIfR), Alexander van den Horst (George Washington University), Chryssa Kouveliotou (George Washington University) and Brendan O'Connor (George Washington University)
on 14 Mar 2020; 22:34 UT
Credential Certification: Kaustubh Rajwade (rkaustubh10@gmail.com)

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Very recently, a candidate new magnetar, SwiftJ1818.0-1607 was discovered by the Burst Alert Telescope (BAT) on the Swift X-ray satellite while in outburst (GCN circular 27373). Further follow-up by NICER (ATel #13551) revealed X-ray pulsations at a nominal period of 1.36 seconds. This triggered a series of follow-up observations using the Effelsberg and the Lovell radio telescopes. The Effelsberg Telescope reported a detection of radio pulsations confirming that the magnetar is in a radio active phase (ATel #13553 ). We used the 76-m Lovell telescope to observe the target on March 14 (MJD 58922) starting from 10:24:41UT for 15 minutes at a central frequency of 1564 MHz. We recorded the data in search mode where a 336 MHz wide band was channelized into 672 channels using a software filterbank. The resultant spectra were combined to have an effective time resolution of 256 microseconds. To mitigate the effects of radio-frequency interference (RFI) on the data, we masked a number of frequency channels resulting in an effective bandwidth of 224 MHz. Finally, the filterbank data were saved to disk for offline processing. We searched the data using the standard pulsar searching software PRESTO to obtain an initial period and DM for the source. After folding and dedispersing the data using these values, the period and DM were optimized using the 'pdmp' software that is part of the standard PSRCHIVE tools (van Straten et al. 2011). A detection with a S/N of 33 corresponding to an approximate flux density of 0.7 +- 0.2 mJy was made with the best barycentric period of 1.36352 +- 0.00001 seconds and DM of 703 +- 7 cm^-3 pc, which is consistent with the values reported in ATel #13553. We attach a link to the detection plot at the bottom of the telegram. Continued follow-up of the source has been planned using the Lovell telescope in order to obtain a timing solution. We encourage multi-wavelength follow-up of the source in its current outburst phase.

Lovell detection plot of Swift J1818.0-1607