2003ApJ...588L..33K

We have detected the optical counterpart to the nearby isolated neutron star RX J1605.3+3249 using observations from the Space Telescope Imaging Spectrometer aboard the Hubble Space Telescope. The counterpart, with m_50CCD=26.84±0.07 mag and very blue colors, lies close to the ROSAT HRI error circle and within the Chandra error circle. The spectrum is consistent with a Rayleigh-Jeans tail whose emission is a factor of ~14 above the extrapolation of the X-ray blackbody, and the source has an unabsorbed X-ray-to-optical flux ratio of log(f_X/f_opt)=4.4, similar to that of other isolated neutron stars. This confirms the classification of RX J1605.3+3249 as a neutron star.