Simultaneous Chandra and VLA Observations of the Transitional Millisecond Pulsar PSR J1023+0038: Anti-correlated X-Ray and Radio Variability

Abstract

We present coordinated Chandra X-ray Observatory and Karl G. Jansky Very Large Array observations of the transitional millisecond pulsar PSR J1023+0038 in its low-luminosity accreting state. The unprecedented five hours of strictly simultaneous X-ray and radio continuum coverage for the first time unambiguously show a highly reproducible, anti-correlated variability pattern. The characteristic switches from the X-ray high mode into a low mode are always accompanied by a radio brightening with duration that closely matches the X-ray low mode interval. This behavior cannot be explained by a canonical inflow/outflow accretion model where the radiated emission and the jet luminosity are powered by, and positively correlated with, the available accretion energy. We interpret this phenomenology as alternating episodes of low-level accretion onto the neutron star during the X-ray high mode that are interrupted by rapid ejections of plasma by the active rotation-powered pulsar, possibly initiated by a reconfiguration of the pulsar magnetosphere, that cause a transition to a less luminous X-ray mode. The observed anti-correlation between radio and X-ray luminosity has an additional consequence: transitional MSPs can make excursions into a region of the radio/X-ray luminosity plane previously thought to be occupied solely by black hole X-ray binary sources. This complicates the use of this luminosity relation to identify candidate black holes, suggesting the need for additional discriminants when attempting to establish the true nature of the accretor.

Peering at the outflow mechanisms in the transitional pulsar PSR J1023+0038: simultaneous VLT, XMM-Newton, and Swift high-time resolution observations

“…The interpretation of this feature is non-trivial. We hypothesize that the flare might be due to the emission of a jet or a non-collimated outflow, as was already suggested by Bogdanov et al (2018). According to our interpretation, the infrared flare would be due to the evolving spectrum of the jet/outflow, the jet-break frequency moving rapidly from higher (NIR) to lower (radio) frequency after the launching of the jet, which has to occur at the low/high mode transition.…”

“…Different scenarios might be considered to explain the lag that we observe between the NIR and optical light curves. Bogdanov et al (2018) observe the emission of radio flares from the system, that the authors interpret as due to the emission of collimated jets in correspondence with the low X-ray state. The spectrum of the radio emission is found to be flat or slightly inverted at the lowest frequencies, which is a typical signature of the emission of synchrotron radiation from jets.…”

“…8). Bogdanov et al (2018) reported on the detection of radio flares emitted in correspondence with the whole duration of an X-ray low mode. During a typical low mode, the radio spectrum of the flare is observed to evolve from being inverted (α ∼ 0.4, where F ν ∝ ν α ) to steep (α ∼ −0.5) over several minutes.…”

“…for the optically thick part (dashed line). After the transition to the high mode, a compact self absorbed jet might be launched (Bogdanov et al 2018). In Fig.…”

NuSTAR and Parkes observations of the transitional millisecond pulsar binary XSS J12270–4859 in the rotation-powered state

“…When in the disc-state, tM-SPs are characterised by a subluminous X-ray emission (LX ∼ 10 33 − 10 34 erg s −1 ) with high, low and flare "modes" (Linares 2014). In IGR J1825-2452 and PSR J1023+0038, the X-ray low-modes were found to be accompained by radio flares in quasi-simultaneous observations (Ferrigno et al 2014;Bogdanov et al 2018), possibly due to outflowing material. Additionally, the presence of X-ray pulses during high X-ray modes in PSRJ1023+0038 (Archibald et al 2015) and J1227 was interpreted as signature of accretion onto the NS.…”