Computer Science – Sound
Scientific paper
Sep 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt.........1w&link_type=abstract
Ph.D. Thesis Colorado Univ., Boulder.
Computer Science
Sound
1
Absorption Spectra, Extreme Ultraviolet Radiation, Stellar Spectra, Ultraviolet Astronomy, White Dwarf Stars, Hydrogen, Photosphere, Rocket Sounding, Stellar Radiation
Scientific paper
The goal of this work is to evaluate the cause(s) of the short wavelength deficit apparent in existing extreme ultraviolet observations of the DA white dwarf G191-B2B. G191-B2B is a hot (Teff approximately equal to 55,000 K) white dwarf located 45 parsecs from earth in the constellation of Aurigae. Observations of G191-B2B with the Al/P and LX3000 photometers onboard the European X ray Observatory (EXOSAT) show the count rate of the Al/P photometer (170 A less than or equal to lambda less than or equal to 300 A) is almost ten times higher than the LX3000 (44 A less than or equal to lambda less than or equal to 300 A) count rate. Pure hydrogen white dwarf model atmospheres predict the photometer count rates should be similar. This discrepancy suggests a short wavelength opacity source(s) is present in the photosphere of G191-B2B. A unique sounding rocket borne instrument with sufficient spectral resolution and sensitivity to investigate the implied opacity source(s) was designed, built, calibrated, and flown. The instrument made observations of G191-B2B between 200 A and 330 A with Delta-lamda = 2 A. The design, calibration, and flight performance of the instrument are discussed. Several absorption features in the spectrum are identified, their statistical significance is evaluated, and potential sources of the features are investigated.
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