A GHRS/HST Spectral Atlas of Sirius-A

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Session 18 -- Stellar Spectra: Individual Objects
Display presentation, Wednesday, January 12, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[18.06] A GHRS/HST Spectral Atlas of Sirius-A

G.M. Wahlgren (CSC/GHRS), Se. Johansson (Univ. Lund), R.L. Kurucz (CfA), D.S. Leckrone (NASA/GSFC)

The Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope has been used to obtain a spectral atlas, covering the wavelength range 1270 - 3200 \AA\ , of the bright star Sirius-A (A1 V). The use of the GHRS first-order gratings provides spectral resolutions between R = 20000 - 35000; however, the rotational velocity (v sin i = 16 km sec$^{-1}$) limits the spectral resolution. The signal-to-noise ratio over most of the spectrum is approximately 200 by photon statistics. The data are being used to understand the ultraviolet line opacity in warm stars. As a result of this work a new model atmosphere for Sirius will be determined, along with corrections to its bolometric correction and elemental abundances. The spectrum also allows us to test and improve current atomic models. A by-product of our work will be more accurate wavelengths and oscillator strengths for the second spectra of the iron-peak elements that will serve as templates for studying the ultraviolet spectra, obtained at lower spectral resolutions, of other warm stars.

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