The first continuous optical monitoring of the transitional millisecond pulsar PSR J1023+0038 with Kepler

Abstract

We report on the first continuous, 80 day optical monitoring of the transitional millisecond pulsar PSR J1023+0038 carried out in mid-2017 with Kepler in the K2 configuration, when an X-ray subluminous accretion disk was present in the binary. Flares lasting from minutes to 14 hr were observed for 15.6% of the time, which is a larger fraction than previously reported on the basis of X-ray and past optical observations, and more frequently when the companion was at the superior conjunction of the orbit. A sinusoidal modulation at the binary orbital period was also present with an amplitude of ~16%, which varied by a few percent over timescales of days, and with a maximum that took place 890 +/- 85 s earlier than the superior conjunction of the donor. We interpret these phenomena in terms of reprocessing of the X-ray emission by an asymmetrically heated companion star surface and/or a non-axisymmetric outflow possibly launched close to the inner Lagrangian point. Furthermore, the non-flaring average emission varied by up to ~ 40% over a time scale of days in the absence of correspondingly large variations of the irradiating X-ray flux. The latter suggests that the observed changes in the average optical luminosity might be due to variations of the geometry, size, and/or mass accretion rate in the outer regions of the accretion disk.

6 pages, 4 figures. Published in ApJ Letters

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• Prolonged sub-luminous state of the new transitional pulsar candidate CXOU J110926.4-650224
• Precise optical timing of PSR J1023+0038, the first millisecond pulsar detected with Aqueye+ in Asiago
• Matter ejections behind the highs and lows of the transitional millisecond pulsar PSR J1023+0038
• The Flare-Dominated Accretion Mode of a Radio-Bright Candidate Transitional Millisecond Pulsar
• Investigating the origin of optical and X-ray pulsations of the transitional millisecond pulsar PSR J1023+0038
• Optical photometry of two transitional millisecond pulsars in the radio pulsar state
• UV and X-ray pulse amplitude variability in the transitional millisecond pulsar PSR J1023+0038
• Peering at the outflow mechanisms in the transitional pulsar PSR J1023+0038: simultaneous VLT, XMM-Newton, and Swift high-time resolution observations
• Multiwavelength evidence for a new flare-mode transitional millisecond pulsar
• A Compact X-Ray Emitting Binary in Likely Association with 4FGL J0935.3+0901
• Revealing a New Black Widow Binary 4FGL J0336.0+7502
• Polarized multiwavelength emission from pulsar wind - accretion disk interaction in a transitional millisecond pulsar
• Exploration of faint X-ray and radio sources in the massive globular cluster M14: A UV-bright counterpart to Nova Ophiuchus 1938
• Probing multi-band variability and mode switching in the candidate transitional millisecond pulsar 3FGL J1544.6-1125