Submillimeter pulsations from the magnetar XTE J1810-197

TL;DR

This study reports the first detection of pulsations from a neutron star in the submillimeter range, specifically from the magnetar XTE J1810-197, demonstrating that neutron star radio emission can extend into this high-frequency regime.

Contribution

It provides the first observational evidence of submillimeter pulsations from a magnetar, expanding the known frequency range of neutron star radio emission.

Findings

Detected pulsations at 353 GHz from XTE J1810-197

Set upper limits at 666 GHz for the first time

Supported the idea of coherent emission mechanisms at high frequencies

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 ($\lambda=0.85\,$mm) in the three epochs, but not detected in the simultaneously-observed band at 666 GHz ($\lambda=0.45\,$mm). We measure an averaged flux density at 353 GHz of 6.7$\pm$1.0, 4.0$\pm$0.6, and 1.3$\pm$0.3 mJy and set 3$\sigma$ 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$>\lambda>$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 turn-up 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.