Multi-Wavelength Emissions From the Millisecond Pulsar Binary PSR J1023+0038 During an Accretion Active State

Abstract

Recent observations strongly suggest that the millisecond pulsar binary PSR J1023+0038 has developed an accretion disk since 2013 June. We present a multi-wavelength analysis of PSR J1023+0038, which reveals that (1) its gammarays suddenly brightened within a few days in 2013 June/July and has remained at a high gamma-ray state for several months; (2) both UV and X-ray fluxes have increased by roughly an order of magnitude; and (3) the spectral energy distribution has changed significantly after the gamma-ray sudden flux change. Time variabilities associated with UV and X-rays are on the order of 100-500 s and 50-100 s, respectively. Our model suggests that a newly formed accretion disk, due to the sudden increase of the stellar wind, could explain the changes of all these observed features. The increase of UV is emitted from the disk, and a new component in gamma-rays is produced by inverse Compton scattering between the new UV component and pulsar wind. The increase of X-rays results from the enhancement of injection pulsar wind energy into the intra-binary shock due to the increase of the stellar wind. We also predict that the radio pulses may be blocked by the evaporated winds from the disk, and the pulsar is still powered by rotation.

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

“…The spectrum is dominated by a blue continuum and strong, double-peaked emission lines of H and He. The spectrum appears similar to other optical spectra of the PSR J1023+0038 binary presented in the literature, both during the active period in 2000/2001 (Bond et al 2002;Wang et al 2009) and 2013/2014 (Halpern et al 2013;Coti Zelati et al 2014;Takata et al 2014). The optical spectra confirm that the accretion disk was present shortly after the end of the 2013 November X-ray observation.…”

“…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.…”

“…Previous studies of PSR J1023+0038 have established that the X-ray emission in the LMXB state is well-described by an absorbed power-law with spectral photon index of 1.7 Γ ≈ with no substantial spectral changes despite the over one order of magnitude variation in flux (Coti Zelati et al 2014;Patruno et al 2014;Takata et al 2014;Tendulkar et al 2014). The large photon harvest of the XMM-Newton data presented here allows us to identify any subtle differences in spectral properties between the three distinct flux modes: low, high, and flare.…”

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

“…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.…”

Gamma-ray pulsars: A gold mine

“…The interaction between the pulsar magnetosphere/wind and the accretion disc is very dynamic, switching between different spectral states in X rays, with and without orbital modulation [98], and producing radio continuum emission and sporadic flares in the optical, UV, and X-rays, suggestive of propellor modes [97]. The γ-ray flux quintupled when the radio pulses disappeared [69,100]. γ-ray emission before the state change was likely powered by the pulsar, yet with only marginal detection of ms pulses [101].…”