The X-ray evolution and geometry of the 2018 outburst of XTE J1810−197. Issue 4 (30th April 2021)

• Record Type: Journal Article
• Authors: Borghese, A; Rea, N; Turolla, R; Rigoselli, M; Alford, J A J; Gotthelf, E V; Burgay, M; Possenti, A; Zane, S; Coti Zelati, F; Perna, R; Esposito, P; Mereghetti, S; Viganò, D; Tiengo, A; Götz, D; Ibrahim, A; Israel, G L; Pons, J; Sathyaprakash, R
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 504:Issue 4(2021)
• Page Start: 5244
• Page End: 5257
• Publication Date: 2021-04-30
• Subjects: stars: individual: XTE J1810−197 -- stars: magnetars -- stars: neutron -- X-rays: bursts; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab1236
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: After 15 yr, in late 2018, the magnetar XTE J1810−197 underwent a second recorded X-ray outburst event and reactivated as a radio pulsar. We initiated an X-ray monitoring campaign to follow the timing and spectral evolution of the magnetar as its flux decays using Swift, XMM–Newton, NuSTAR, and NICER observations. During the year-long campaign, the magnetar reproduced similar behaviour to that found for the first outburst, with a factor of 2 change in its spin-down rate from ∼7.2 × 10 −12 to ∼1.5 × 10 −11 s s −1 after two months. Unique to this outburst, we confirm the peculiar energy-dependent phase shift of the pulse profile. Following the initial outburst, the spectrum of XTE J1810−197 is well modelled by multiple blackbody components corresponding to a pair of non-concentric, hot thermal caps surrounded by a cooler one, superposed to the colder star surface. We model the energy-dependent pulse profile to constrain the viewing and surface emission geometry and find that the overall geometry of XTE J1810−197 has likely evolved relative to that found for the 2003 event.