Engulfing a radio pulsar: the case of PSR J1023+0038

Abstract

The binary millisecond radio pulsar PSR J1023+0038 has been recently the subject of multi-wavelength monitoring campaigns which revealed that an accretion disc has formed around the neutron star (since 2013 June). We present here the results of Xray and UV observations carried out by the Swift satellite between 2013 October and 2014 May, and of optical and NIR observations performed with the REM telescope, the Liverpool Telescope, the 2.1-m telescope at the San Pedro Mártir Observatory and the 1.52-m telescope at the Loiano observing station. The X-ray spectrum is well described by an absorbed power law, which is softer than the previous quiescent epoch (up to 2013 June). The strong correlation between the X-ray and the UV emissions indicates that the same mechanism should be responsible for part of the emission in these bands. Optical and infrared photometric observations show that the companion star is strongly irradiated. Double-peaked emission lines in the optical spectra provide compelling evidence for the presence of an outer accretion disc too. The spectral energy distribution from IR to X-rays is well modelled if the contributions from the companion, the disc and the intra-binary shock emission are all considered. Our extensive data set can be interpreted in terms of an engulfed radio pulsar: the radio pulsar is still active, but undetectable in the radio band due to a large amount of ionized material surrounding the compact object. X-rays and gamma-rays are produced in an intra-binary shock front between the relativistic pulsar wind and matter from the companion and an outer accretion disc. The intense spin-down power irradiates the disc and the companion star, accounting for the UV and optical emissions.

Different twins in the millisecond pulsar recycling scenario: Optical polarimetry of PSR J1023+0038 and XSS J12270-4859

“…8. NIR-optical contemporaneous SED of J1023 obtained in this work (orbital phase 0.59; blue squares); the NIR−X-rays SED of J1023 reported in Coti Zelati et al (2014) is also represented (red dots), with superimposed the fit with a model made by the companion star (red dashed line), the accretion disc (green dash-dotted line), and the shock emission powered by the NS spin-down luminosity (blue dotted line).…”

“…The system has been the subject of extensive multi-wavelength campaigns after its change of state (Halpern et al 2013;Kong 2013;Linares et al 2014;Patruno et al 2014;Takata et al 2014;Tendulkar et al 2014;Coti Zelati et al 2014;Deller et al 2015;Archibald et al 2015;Bogdanov et al 2015;Shahbaz et al 2015). Radio band observations performed by Deller et al (2015), in particular, showed a rapidly variable and flat spectrum that persisted over six months.…”

“…Unfortunately, we did not possess contemporaneous datasets in all of the bands. However, in the case of J1023 our group possessed a more refined photometric analysis (already published in Coti Zelati et al 2014) that referred to an earlier epoch (end of 2013). Thanks to this analysis we obtained reliable parameters of the sinusoidal functions that describe the light curves trend in the optical.…”

“…Regarding J1023, we tried a comparison between our NIR-optical simultaneous points with the results reported in Coti Zelati et al 2014 (referring to observations carried out in Nov. 2013; Fig. 8).…”

Coordinated X-Ray, Ultraviolet, Optical, and Radio Observations of the PSR J1023+0038 System in a Low-Mass X-Ray Binary State

“…Swift has been used to regularly monitor the long-term behavior of PSR J1023+0038 since 2013 October (Coti Zelati et al 2014;Patruno et al 2014;Takata et al 2014). It observed the binary on 2013 November 10-13 and 2014 June 11 coincident with the XMM-Newton exposures.…”