The First Continuous Optical Monitoring of the Transitional Millisecond Pulsar PSR J1023+0038 with Kepler
Date Issued
2018
Author(s)
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Rea, N.
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Coti Zelati, F.
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Scaringi, S.
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de Ońa Wilhelmi, E.
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Knigge, C.
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Serenelli, A.
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Torres, D. F.
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•
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 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 this 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 timescale 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.
Volume
858
Issue
2
Start page
L12
Issn Identifier
2041-8205
Ads BibCode
2018ApJ...858L..12P
Rights
open.access
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