The 2018 X-ray and Radio Outburst of Magnetar XTE J1810-197

Abstract

We present the earliest X-ray observations of the 2018 outburst of XTE J1810-197, the first outburst since its 2003 discovery as the prototypical transient and radio-emitting anomalous X-ray pulsar (AXP). The Monitor of All-sky X-ray Image (MAXI) detected XTE J1810-197 immediately after a November 20-26 visibility gap, contemporaneous with its reactivation as a radio pulsar, first observed on December 8. On December 13 the Nuclear Spectroscopic Telescope Array (NUSTAR) detected X-ray emission up to at least 30 keV, with a spectrum well-characterized by a blackbody plus power-law model with temperature kT = 0.74+/-0.02 keV and photon index Gamma = 4.4+/-0.2 or by a two-blackbody model with kT = 0.59+/-0.04 keV and kT = 1.0+/-0.1 keV, both including an additional power-law component to account for emission above 10 keV, with Gamma_h = -0.2+/-1.5 and Gamma_h = 1.5+/-0.5, respectively. The latter index is consistent with hard X-ray flux reported for the non-transient magnetars. In the 2-10 keV bandpass, the absorbed flux is 2E-10 erg/s/cm^2, a factor of 2 greater than the maximum flux extrapolated for the 2003 outburst. The peak of the sinusoidal X-ray pulse lags the radio pulse by approx. 0.13 cycles, consistent with their phase relationship during the 2003 outburst. This suggests a stable geometry in which radio emission originates on magnetic field lines containing currents that heat a spot on the neutron star surface. However, a measured energy-dependent phase shift of the pulsed X-rays suggests that all X-ray emitting regions are not precisely co-aligned.

7 pages, 4 Figues, 1 Table, Latex, emulateapj style; Added Table/Figure for the 3-30 keV spectral results. Astrophysical Journal Letters, in Press

References in corpus (11)

• Transient pulsed radio emission from a magnetar
• Untwisting magnetospheres of neutron stars
• 1E 1547.0-5408: a radio-emitting magnetar with a rotation period of 2 seconds
• Distances to Anomalous X-ray Pulsars using Red Clump Stars
• Polarized radio emission from a magnetar
• Outburst of the 2 s Anomalous X-ray Pulsar 1E 1547.0-5408
• The UTMOST: A hybrid digital signal processor transforms the MOST
• The Anatomy of a Magnetar: XMM Monitoring of the Transient Anomalous X-ray Pulsar XTE J1810-197
• Constraints on the Emission and Viewing Geometry of the Transient Anomalous X-ray Pulsar XTE J1810-197
• A broadband X-ray study of the Geminga pulsar with NuSTAR and XMM-Newton
• Neutral Hydrogen Absorption Toward XTE J1810-197: the Distance to a Radio-Emitting Magnetar

Cited by in corpus (6)

• The Thousand-Pulsar-Array programme on MeerKAT I: Science objectives and first results
• The dynamic magnetosphere of Swift J1818.0$-$1607
• Discovery of ASKAP J173608.2-321635 as a Highly-Polarized Transient Point Source with the Australian SKA Pathfinder
• The long-term enhanced brightness of the magnetar 1E 1547.0-5408
• Detection of the magnetar XTE J1810-197 at 150 and 260 GHz with the NIKA2 Kinetic Inductance Detector camera
• High Frequency Radio Observations of Two Magnetars, PSR J1622$-$4950 and 1E 1547.0$-$5408