Time Evolution and the Nature of the Near-Infrared Jets in GRS 1915+105

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Abstract
We observed the Galactic microquasar GRS 1915+105 in the K (2.2 μm) band on 1995 October 16 and 17 UTC using the cryogenic optical bench (COB) infrared imager on the Kitt Peak National Observatory 2.1 m telescope with a 02 pixel-1 plate scale and under good (~07) seeing conditions. Using a neighboring star in the image frames to determine the point-spread function (PSF), we PSF-subtract the images of GRS 1915+105. We find no evidence of extended emission such as the apparent near-IR jets seen by Sams, Eckart, & Sunyaev in 1995 July. Simple modeling of the star plus jet structure allows us to place an upper limit on any similar emission at that position of K > 16.4 at the 95% confidence level, as compared to K = 13.9 as seen by Sams et al. This lack of extended IR flux during continued hard X-ray flaring activity confirms the hypothesis that the extended IR emission arises from the superluminal radio-emitting jets rather than reprocessing of the X-ray emission on other structures around the compact central object. Given the large apparent velocity of the radio-emitting jets, by the time of our observations the Sams et al. feature would have moved more than 1'' from GRS 1915+105, and we can place a limit of K > 17.7 (95% confidence level) on any infrared emission in this region. We can thus place an upper limit of τ < 28 days on the radiative timescale of the feature, which is consistent with synchrotron jet emission.
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