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Infrared Observations of The Millisecond Pulsar Binary J1023+0038: Evidence for Short-Term Nature of Its Interacting Phase in 2000--2001

We report our multi-band infrared (IR) imaging of the transitional millisecond pulsar system J1023+0038, a rare pulsar binary known to have an accretion disk in 2000--2001. The observations were carried out with ground-based and space telescopes from near-IR to far-IR wavelengths. We detected the source in near-IR JH bands and Spitzer 3.6 and 4.5 $μ$m mid-IR channels. Combined with the previously-reported optical spectrum of the source, the IR emission is found to arise from the companion star, with no excess emission detected in the wavelength range. Because our near-IR fluxes are nearly equal to those obtained by the 2MASS all-sky survey in 2000 Feb., the result indicates that the binary did not contain the accretion disk at the time, whose existence would have raised the near-IR fluxes to 2-times larger values. Our observations have thus established the short-term nature of the interacting phase seen in 2000--2001: the accretion disk at most existed for 2.5 yrs. The binary was not detected by the WISE all-sky survey carried out in 2010 at its 12 and 22 $μ$m bands and our Herschel far-IR imaging at 70 and 160 $μ$m. Depending on the assumed properties of the dust, the resulting flux upper limits provide a constraint of <3x10^{22}--3x10^{25} g on the mass of the dust grains that possibly exist as the remnant of the previously-seen accretion disk.