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

Abstract

The PSR J1023+0038 binary system hosts a neutron star and a low-mass, main-sequence-like star. It switches on year timescales between states as an eclipsing radio millisecond pulsar and a low-mass X-ray binary (LMXB). We present a multi-wavelength observational campaign of PSR J1023+0038 in its most recent LMXB state. Two long XMM-Newton observations reveal that the system spends ∼70% of the time in a ≈3 × 10 33 erg s −1 X-ray luminosity mode, which, as shown in Archibald et al., exhibits coherent X-ray pulsations. This emission is interspersed with frequent lower flux mode intervals with 5 10 32 ≈ × erg s −1 and sporadic flares reaching up to ≈10 34 erg s −1 , with neither mode showing significant X-ray pulsations. The switches between the three flux modes occur on timescales of order 10 s. In the UV and optical, we observe occasional intense flares coincident with those observed in X-rays. Our radio timing observations reveal no pulsations at the pulsar period during any of the three X-ray modes, presumably due to complete quenching of the radio emission mechanism by the accretion flow. Radio imaging detects highly variable, flat-spectrum continuum radiation from PSR J1023+0038, consistent with an origin in a weak jet-like outflow. Our concurrent X-ray and radio continuum data sets do not exhibit any correlated behavior. The observational evidence we present bears qualitative resemblance to the behavior predicted by some existing "propeller" and "trapped" disk accretion models although none can account for key aspects of the rich phenomenology of this system.

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 J1023+0038 pulsar provides a useful test bed at a distance of 1.37 kpc toward the γ-ray source 2FGLJ1023.6+0040: an accretion disc was observed in the optical in 2000-2001; the detection of radio pulses from a MSP followed in 2007, until the pulses disappeared in 2013, quenched or eclipsed by the ionized flow from a new X-ray accretion disc [97,98,99]. 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].…”

Formation Constraints Indicate a Black Hole Accretor in 47 Tuc X9

“…At the observed X-ray luminosity (a few ×10 33 erg s −1 ) accreting neutron stars only rarely show similar radio luminosities, and these systems are nearly all "transitional" millisecond pulsars that also show unusual, short-term X-ray and radio variability not seen in X9 (e.g. Bogdanov et al 2015;Deller et al 2015). Nonetheless, the phenomenology of accreting neutron stars at these X-ray luminosities is not well understood.…”