Accretion-powered pulsations in an apparently quiescent neutron star binary

Abstract

Accreting millisecond X-ray pulsars are an important subset of low-mass X-ray binaries in which coherent X-ray pulsations can be observed during occasional, bright outbursts (X-ray luminosity $L_X\sim 10^{36}$ erg s${}^{-1}$). These pulsations show that matter is being channeled onto the neutron star's magnetic poles. However, such sources spend most of their time in a low-luminosity, quiescent state ($L_X\lesssim 10^{34}$ erg s${}^{-1}$), where the nature of the accretion flow onto the neutron star (if any) is not well understood. Here we report that the millisecond pulsar/low-mass X-ray binary transition object PSR J1023+0038 intermittently shows coherent X-ray pulsations at luminosities nearly 100 times fainter than observed in any other accreting millisecond X-ray pulsar. We conclude that in spite of its low luminosity PSR J1023+0038 experiences episodes of channeled accretion, a discovery that challenges existing models for accretion onto magnetized neutron stars.

9 pages, 7 figures, 1 table; accepted in ApJ

References in corpus (1)

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

Cited by in corpus (11)

• Discovery of PSR J1227-4853: A transition from a low-mass X-ray binary to a redback millisecond pulsar
• Identification of the High-Energy Gamma-Ray Source 3FGL J1544.6-1125 as a Transitional Millisecond Pulsar Binary in an Accreting State
• The nature of very faint X-ray binaries; hints from light curves
• Discovery of Gamma-ray Pulsations from the Transitional Redback PSR J1227-4853
• A Search for Very High-Energy Gamma Rays from the Missing Link Binary Pulsar J1023+0038 with VERITAS
• Coordinated X-ray, Ultraviolet, Optical, and Radio Observations of the PSR J1023+0038 System in a Low-mass X-ray Binary State
• A propeller model for the sub-luminous disk state of the transitional millisecond pulsar PSR J1023+0038
• Binary evolution with LOFT
• The Swift X-ray monitoring campaign of the center of the Milky Way
• Limits on thermal variations in a dozen quiescent neutron stars over a decade
• A Low-Mass Main-Sequence Star and Accretion Disk in the Very Faint Transient M15 X-3