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We report on Chandra X-ray and Gemini-North near-infrared K-band observationsof the eclipsing accretion-powered millisecond X-ray pulsar SWIFT J1749.4-2807in quiescence. Using the Chandra observation we derive a source position ofRight Ascencion: 17:49:31.73 and Declination:-28:08:05.08. The position isaccurate to 0.6" (90 per cent confidence). We find one source at a magnitudeK=18.44+-0.03 with a position fully consistent with the accurate Chandra X-raylocalization and a second source at K=19.2+-0.1 that falls close to the edge ofthe error circle in the deep K-band images. The presence of a few weakersources as suggested by previous H-band observations presented in theliterature cannot the ruled out. There is marginal evidence that the brighterof the these two sources is variable. Follow-up spectroscopy of this potentialcounterpart will show if this source is the true counterpart to SWIFTJ1749.4-2807. If so, baring the presence of complicating effects such asheating of the mass-donor star, it would allow for the mass of the neutron starto be measured through the measurement of periodic radial velocity variations.

Chandra X-ray and Gemini near-infrared observations of the eclipsing msec pulsar SWIFT J1749.4-2807 in quiescence