High-cadence observations and variable spin behaviour of magnetar Swift J1818.0−1607 after its outburst

Abstract

We report on multi-frequency radio observations of the new magnetar Swift J1818.0−1607, following it for more than one month with high cadence. The observations commenced less than 35 hours after its registered first outburst. We obtained timing, polarisation and spectral information. Swift J1818.0−1607 has an unusually steep spectrum for a radio emitting magnetar and also has a relatively narrow and simple pulse profile. The position angle swing of the polarisation is flat over the pulse profile, possibly suggesting that our line-of-sight grazes the edge of the emission beam. This may also explain the steep spectrum. The spin evolution shows large variation in the spin-down rate, associated with four distinct timing events over the course of our observations. Those events may be related to the appearance and disappearance of a second pulse component. The first timing event coincides with our actual observations, while we did not detect significant changes in the emission properties which could reveal further magnetospheric changes. Characteristic ages inferred from the timing measurements over the course of months vary by nearly an order of magnitude. A longer-term spin-down measurement over approximately 100 days suggests an characteristic age of about 500 years, larger than previously reported. Though Swift J1818.0−1607 could still be one of the youngest neutron stars (and magnetars) detected so far, we caution using the characteristic age as a true-age indicator given the caveats behind its calculation.

Multi-frequency radio observations of the radio-loud magnetar XTE J1810-197

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Global Sky Models can Improve Flux Estimates in Pulsar and FRB Studies

“…Limiting the search to papers published in 2020, fifteen papers were returned by ADS, of which eleven employed SISH. Of these, seven papers used a value of β = −2.55 (Bilous et al 2020;Bondonneau et al 2020;Champion et al 2020;Chawla et al 2020;van Leeuwen et al 2020;Parent et al 2020;Tan et al 2020), three papers used β = −2.6 (Agarwal et al 2020;Basu et al 2020;Oostrum et al 2020), and one paper used β = −2.5 (Good et al 2020).…”

Probing magnetar formation channels with high-precision astrometry: The progress of VLBA astrometry of the fastest-spinning magnetar Swift J1818.0-1607

“…The progress of astrometry of Swift J1818.0−1607 Swift J1818.0−1607 is the fifth discovered radio-bright (Karuppusamy et al 2020) magnetar (GCN circular 27373), which is also the hitherto fastest-spinning magnetar with a spin period of 1.4 s (Enoto et al 2020). Its short spin period and high spindown rate correspond to a characteristic age of around 500 yr (Champion et al 2020), implying its great youth. Right after the radio detection of Swift J1818.0−1607, we launched an astrometric campaign of the magnetar using the Very Long Baseline Array (VLBA).…”