The 11 yr of low activity of the magnetar XTE J1810−197. Issue 3 (11th December 2018)

• Record Type: Journal Article
• Authors: Pintore, Fabio; Mereghetti, Sandro; Esposito, Paolo; Turolla, Roberto; Tiengo, Andrea; Rea, Nanda; Bernardini, Federico; Israel, Gian Luca
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 483:Issue 3(2019)
• Page Start: 3832
• Page End: 3838
• Publication Date: 2018-12-11
• Subjects: magnetic fields -- stars: magnetars -- stars: neutron -- pulsars: individual: XTE J1810-197 -- X-rays: stars; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty3378
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: In 2003, the magnetar XTE J1810−197 started an outburst that lasted until early 2007. In the following 11 yr, the source stayed in a quiescent/low-activity phase. XTE J1810−197 is one of the closest magnetars, hence its X-ray properties can be studied in detail even in quiescence and an extended monitoring has been carried out to study its long-term timing and spectral evolution. Here, we report the results of new X-ray observations, taken between 2017 September and 2018 April, with XMM–Newton, Chandra, and NICER . We derived a phase-connected timing solution yielding a frequency derivative of −9.26(6) × 10 −14 Hz s −1 . This value is consistent with that measured between 2009 and 2011, indicating that the pulsar spin-down rate remained quite stable during the long quiescent period. A spectral analysis of all the X-ray observations taken between 2009 and 2018 does not reveal significant spectral and/or flux variability. The spectrum of XTE J1810−197 can be described by the sum of two thermal components with temperatures of 0.15 and 0.3 keV, plus a power-law component with photon index 0.6. We also found evidence for an absorption line at ∼1.2 keV and width of 0.1 keV. Due to the long exposure time of the summed XMM–Newton observations, we could also carry out a phase-resolved spectral analysis for this source in quiescence. This showed that the flux modulation can be mainly ascribed to the warmer of the two thermal components, whose flux varies by ∼45 per cent along the pulse phase.