Program: GN-2012A-Q-67

Last year it was discovered that the peculiar transient SWIFT J1749.4-2807 exhibits pulsations at 518 Hz. Furthermore, it turned out that the source was eclipsing in a 8.8 hr orbit thereby holding the promise of a model independent neutron star mass determination. Optical or near-infrared dynamical studies offer the best prospects for constraining the neutron star equation of state, as they do not rely on any specific models concerning the neutron star itself. Unfortunately, the source position of SWIFT J1749.4-2807 is not well know at present. The unique focusing capabilities of Chandra will provide the source position via our approved Chandra observation. Here, we propose for Gemini near-infrared imaging, to locate the near-infrared counterpart of the source. The time 0.2 hrs has been awarded via the Chandra TAC.