The Vela Pulsar in the Ultraviolet

Abstract

We describe time-tagged observations of the Vela pulsar (PSR B0833-45) with the HST STIS MAMA UV detectors. Using an optimal extraction technique, we obtain an NUV light curve and crude FUV phase-resolved spectra. The pulse is dominated by complex nonthermal emission at all phases. We obtain approximate spectral indices for the brightest pulse components, relate these to pulsations observed in other wave bands, and constrain the thermal surface emission from the neutron star. An upper limit on the Rayleigh-Jeans component at UV pulse minimum suggests a rather low mean surface temperature T^∞_eff<4.6×10⁵(d₃₀₀/R_14.2)² K. If confirmed by improved phase-resolved spectroscopy, this observation has significant impact on our understanding of neutron star interiors.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.