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Session 111 - Pulsars.
Display session, Saturday, January 10
Exhibit Hall,
We present the spectrum and pulse profile of the Crab Pulsar in the near ultraviolet (1600-3200Åwith the Space Telescope Imaging Spectrograph (STIS) during the Hubble Space Telescope (HST) Second Servicing Mission Orbital Verification (SMOV) period. The two-dimensional Near Ultraviolet Multi-Anode Microchannel Array (NUV-MAMA) was used in time-tag mode with a 2\arcsec \times 2\arcsec aperture and the low dispersion grating, G230L, to obtain a three dimensional data cube in detector coordinates and time. The internally derived pulse period is consistent with radio measurements, and the pulse profile agrees well with previous near ultraviolet broadband measurements by the High Speed Photometer. The pulsar spectrum includes the 2200Ådiffuse feature, plus several interstellar absorption lines. Dereddening the spectrum using the Savage-Mathis model with E(B-V)=0.55 \pm 0.05 leads to a good fit to a power law with slope \alpha _\nu= -0.3 \pm 0.2 . Spectra of the primary pulse, the interpulse, the individual rising edges and falling edges are similar to the total spectrum to the limits of photon statistics. Breaking the spectrum into 200Åbins and comparing the pulse and interpulse profiles shows the profiles to be stable across the NUV spectral range. Histogram analysis reveals no evidence for giant pulses as seen at radio wavelengths.
