Multi-band observations of Swift J1818.0-1607 with Parkes
ATel #13587; Marcus E. Lower (Swinburne University of Technology, SUT) and Ryan M. Shannon (SUT)
on 25 Mar 2020; 01:09 UT
Credential Certification: Marcus Lower (mlower@swin.edu.au)
Subjects: Radio, Neutron Star, Soft Gamma-ray Repeater, Pulsar, Magnetar
We performed target of opportunity observations of the newly discovered radio-loud magnetar Swift J1818.0-1609 (GCN #27373; ATel #13553) with the Parkes radio telescope using the central beam of the 20-cm multi-beam receiver (1.369 GHz central frequency, 256 MHz bandwidth) at UTC 2020-03-16-18:12 and the Mars X-band receiver (8.5 GHz, 512 MHz effective bandwidth) at UTC 2020-03-20-16:28.
Both observations were conducted in pulsar search-mode with four coherency products recorded. The data were folded and dispersion corrected using the values published in ATel #13562. We detected the magnetar in the 1458 s multi-beam observation with a S/N of 77. Using the radiometer equation and published system performance parameters, we obtain a flux density of 0.7 mJy at 1.369 GHz. Fitting the phase-integrated Stokes Q & U spectra, we obtain a rotation measure of 1445 +/- 2 rad/m^-2 (68.3% C.I.) which is consistent with the value measured in ATel #13553.
Similar to ATel #13575, we do not detect periodic emission at X-band after averaging our 3616 s observation in time, frequency and polarisation. Using the radiometer equation and a threshold S/N of 7, we place an upper-limit on the flux density of < 0.05 mJy at 8.5 GHz. A preliminary search of the data with Heimdall showed no evidence for individual pulses with a signal to noise ratio greater than 7 and a dispersion measure consistent with the magnetar.
Figures showing the polarisation profile at 1.369 GHz and posterior distributions for the rotation measure fit are available at the link below.
We would like to thank the ATNF staff, in particular James Green and Stacy Mader, for allocating time to perform these observations and assistance in setting up the Mars receiver.
Parkes L-band detection and rotation measure fitting of Swift J1818.0-1607