Optical Observations of the Binary MSP J1023+0038 in a New Accreting State

ATel #5514; J. P. Halpern (Columbia U.), E. Gaidos (U. Hawaii Manoa), A. Sheffield, A. M. Price-Whelan, S. Bogdanov (Columbia U.)
on 25 Oct 2013; 19:10 UT
Credential Certification: Jules Halpern (jules@astro.columbia.edu)

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Following the disappearance of radio pulsations from the binary MSP J1023+0038 (Stappers et al., ATel #5513), we began optical monitoring at the MDM Observatory on Kitt Peak after the source emerged from solar conjunction. Using the 1.3m McGraw-Hill telescope, we obtained nightly V-band photometry of the PSR J1023+0038 system in morning twilight, from 2013 October 16−23 UT. Magnitudes were measured relative to the calibrated secondary standard stars in the finding chart of Thorstensen & Armstrong (2005). These authors show an orbital light curve in quiescence during 2004 May, in which the modulation is dominated by heating of the side of the companion star facing the pulsar. A direct comparison can be made between each of our 5-minute exposures and the historical magnitude V_ref at the matching phase of the 4.75 hr orbit. We extrapolated the radio orbital ephemeris of Archibald et al. (2009). Allowing for combined statistical and systematic errors of ~0.05 mag, there is evidence for night-to-night variations and an overall elevation in brightness ΔV of up to −1 mag from the quiescent level. Only ~1/3 of the orbital phase is sampled because the period is nearly commensurate with 1 day.

MJD (helio)  V (mag)  V_ref  ΔV

56581.5246 16.89 17.65 −0.76
56582.5135 16.94 17.65 −0.71
56582.5289 16.76 17.60 −0.84
56583.5105 16.86 17.63 −0.77
56583.5210 16.84 17.60 −0.76
56583.5261 16.76 17.55 −0.79
56583.5311 16.76 17.53 −0.77
56584.5209 16.51 17.53 −1.02
56584.5269 16.57 17.48 −0.91
56584.5321 16.47 17.46 −0.99
56585.5267 16.41 17.44 −1.03
56585.5318 16.41 17.44 −1.03
56586.5231 16.56 17.40 −0.84
56586.5281 16.57 17.37 −0.80
56586.5331 16.45 17.36 −0.91
56587.5168 16.57 17.38 −0.81
56587.5222 16.43 17.36 −0.93
56587.5271 16.39 17.35 −0.96
56588.5116 16.37 17.36 −0.99
56588.5166 16.44 17.35 −0.91
56588.5210 16.44 17.35 −0.91

A small number of exposures in the B filter were acquired that indicate B-V in the range 0.39-0.48. This is bluer than the quiescent B-V color in Thorstensen & Armstrong (2005), which varies from 0.60 to 0.76 around the orbit.

A 15 minute spectrum was obtained on 2013 October 22 12:18 UT using the 2.4m Hiltner telescope with Modspec. The wavelength coverage was 5140−7220 Å at 3.7 Å resolution. Emission lines of Hα, He I λ5876, and He I λ6678 are seen. The Hα line is double peaked with a peak separation of 740 km s^-1, and FWZI = 3500 km s^-1, indicative of circular motion in an accretion disk. Its equivalent width is −19 Å. These values are very similar to those of the SDSS spectrum from 2001 February 1 analyzed by Wang et al. (2009), which was the previous time that emission lines were seen from this object. Additional 20 minute exposures obtained on 2013 October 24 12:06 UT and October 25 12:05 UT look similar to the first one. For comparison, the G5 type spectrum from 2004 that has no emission lines can be seen in Thorstensen & Armstrong (2005).

Optical Spectra