Submillimeter pulsations from the magnetar XTE J1810-197

Abstract

We present the first detection of pulsations from a neutron star in the submillimeter range. The source is the magnetar XTE J1810−197, observed with the James Clerk Maxwell Telescope (JCMT) on 2020 February 27, 2020 July 9 and 2021 May 15. XTE J1810−197 is detected at 353 GHz (λ =0.85 mm) in the three epochs, but not detected in the simultaneously-observed band at 666 GHz (λ =0.45 mm). We measure an averaged flux density at 353 GHz of 6.7±1.0, 4.0±0.6, and 1.3±0.3 mJy and set 3σ flux density upper limits at 666 GHz of 11.3, 4.7 and 4.3 mJy, at each of the three observing epochs, respectively. Combining close-in-time observations with the Effelsberg 100m and IRAM 30m telescopes covering non-contiguously from 6 to 225 GHz (5.0 cm> λ >1.33 mm), we investigate the spectral shape and frequency range of a potential spectral turn-up predicted by some pulsar radio emission models. The results demonstrate that the beamed radio emission from neutron stars can extend into the submillimeter regime, but are inconclusive on the existence and location of a potential spectral turnup within the covered frequency range. The observed properties of the submillimeter emission resemble those of the longer wavelengths, and support a coherent mechanism for the production of pulsations at 353 GHz.

Magnetar XTE J1810-197: Spectro-temporal evolution of average radio emission

“…The radio emission typically has a flat spectrum. This has enabled the study of the radio emission at radio frequencies as Corresponding author: Yogesh Maan ymaan@ncra.tifr.res.in 1 http://www.physics.mcgill.ca/ ∼ pulsar/magnetar/main.html high as 353 GHz for some of the radio-loud magnetars (Torne et al 2022). The very high frequency observations indicate that the radio spectrum has a high frequency turn-up.…”