Interstellar extinction and ultraviolet flux distribution of the crabnebula.
Abstract
Five-band ultraviolet spectrophotometry of the central 2'.5 × 2'.5 area of the Crab Nebula is reported. The ultraviolet magnitudes of 40 0 and B stars within a circle of 10° radius from the nebula are also given. Of these, eight stars are found to be suitable for establishing the reddening law of this region. The result is Aλ/E(B-V) = 8.53±0.ll, 8.09±0.09, 9.88±0.08, 7.26±0.07, and 4.98±0.03, respectively, at 1550, 1800, 2200, 2500, and 3300 Å. With the above extinction curve, the method which uses the 2200 A dust absorption feature to derive the amount of reddening yields E(B-V) = 0.50±0.03 for the Crab Nebula. The dereddened UV spectrum is a power law of spectral index 0.50. When the ANS fluxes are normalized at 3300 Å to the ground-based measurement for the whole nebula, the power law can be described by log fv = -0.50 log v - 14.95. Optical and infrared data are extracted from the literature. The dereddened optical fluxes can be fitted by a power law of log fv = -0.43 log v - 15.99. The infrared fluxes are consistent with the extrapolated optical power law. A spectral steepening between 2500 and 3300 Å is suggested.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1981
- DOI:
- 10.1086/158833
- Bibcode:
- 1981ApJ...245..581W
- Keywords:
-
- Crab Nebula;
- Interstellar Extinction;
- Supernova Remnants;
- Ultraviolet Radiation;
- Ultraviolet Spectra;
- B Stars;
- Continuous Radiation;
- Infrared Radiation;
- O Stars;
- Red Shift;
- Stellar Magnitude;
- Ultraviolet Spectrophotometers;
- Astronomy