Follow up of the radio flare from the magnetar XTE J1810-197 at 1.4 GHz

ATel #12323; Authors (affiliation): S. del Palacio (IAR, Argentina), F. Garcia (CEA, France), L. Combi (IAR, Argentina), F. Lopez Armengol (IAR, Argentina), G. Gancio (IAR, Argentina), A. L. Muller (IAR, Argentina), P. Kornecki (IAR, Argentina) report on behalf of the PuMA Collaboration
on 22 Dec 2018; 18:00 UT
Credential Certification: Santiago del Palacio (santiagodp1990@gmail.com)

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The magnetar XTE J1810-197 has experienced periods of activity in X-rays (Ibrahim et al. 2004) and in radio frequencies, being the first magnetar in which radio pulsations were detected (Camilo et al. 2006). After being in a radio-quiet state for several years (Camilo et al. 2016), this magnetar has recently re-entered in outburst (ATEL #12284, #12285). The IAR (Argentinian Institute of Radioastronomy, https://www.iar.unlp.edu.ar/ ) is going through major upgrades to suit its two 30-m antennas for pulsar timing investigations performed by the PuMA (Pulsar Monitoring in Argentina http://puma.iar.unlp.edu.ar/ ) collaboration. As an exploratory study, we dedicated observing time to the transient XTE J1810-197 during December 14 (MJD 58466.615), December 19 (MJD 58471.614) and December 20 (MJD 58472.615). Single-polarization observations with a bandwidth of 56 MHz centered at 1420 MHz revealed significant pulsating radio emission from XTE J1810-197 with a barycentric spin-period of P = 5.54137(3) s on MJD 58466.615, consistent with the values reported in ATEL #12284, and #12312. In subsequent observations we obtained signal-to-noise ratios of 16 for a 90-min observation (Antenna 2, Dec. 14), 24 for 150-min observation (Antenna 1, Dec. 19), 10 for a 80-min observation (Antenna 2, Dec. 19) on the first polarization and 14 on the second polarization, and 15 for a 50-min observation (Antenna 2, Dec. 20). Unfortunately, we could not derive polarization angles and calibrated fluxes with these measurements. The pulse profiles from Dec. 14 showed a complex structure of a short, strong peak preluded by a less intense and longer in duration precursor ( Dec. 14 pulse profile at 1400 MHz), as reported at other frequencies in ATEL #12284, #12285, and #12312. In turn, the precursor peak is not visible on subsequent observations from Dec. 19 ( Dec. 19 pulse profile at 1400 MHz) and Dec. 20 ( Dec. 20 pulse profile at 1400 MHz). We will continue performing daily monitoring of the source at 1.4 GHz, although its proximity to the Sun now forces us to interrupt the follow up for about ten days.