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Analysis of Voyager spectra of the beta Cephei star nu EridaniVoyager 500-1700 A spectrophotometric observations of the beta Cephei star nu Eri are presented and discussed. The Voyager observations were obtained in 1981 and cover six pulsation cycles of the star. These data are supplemented with a set of nine International Ultraviolet Explorer (IUE) SWP high-resolution observations covering one, earlier epoch, pulsation cycle. Light curves are derived from the Voyager data at 1055 and 1425 A. These light curves are found to be consistent in both shape and period with published optical curves. The 1055 A light curve also exhibits a phenomenon not seen in the optical curves: a small but highly significant systematic increase in the flux of the maximum light phases while maintaining a constant minimum light level over the interval of observation. Substantially larger errors in the longer wavelength data preclude discussion of this phenomenon in the 1425 A light curve. Examination of the far-UV continuum in nu Eri during this period shows that the color temperature is lower for the brighter maxima. Analysis of the far-UV continuum at maximum and minimum light yields an effective temperature difference between these two phases of 2200 + or - 750 K. Spectroscopically, three prominent features are seen in the Voyager data: a feature at 985 A mostly due to a blend of C III 977 A, H I Ly gamma 972 A, and N III 990 A; a feature at 1030 A due to H I Ly beta 1026 A and C II 1037 A; and the Si IV resonance doublet near 1400 A. A comparison of the 912-1700 A spectral region in nu Eri with a set of standard, i.e., nonpulsating stars, shows that nu Eri closely resembles the standard both in continuum shape and spectral line strengths with the possible exception of a slight flux excess between 912 and 975 A. The equivalent width of the 985 A feature is shown to vary in strength over the pulsation cycle in antiphase with the light curve and variations seen in the C IV 1548-1551 lines from the IUE data. This behavior of the 985 A feature is most likely caused by variations in the strength of the Ly gamma component of the blend. Comparisons are also made between nu Eri and the only other beta Cephei star studied in the far-UV, BW Vul, with the most notable differences between the two stars being the much larger delta(T(sub eff)) for BW Vul and the almost total absence of abnormalities in observed spectrum of nu Eri.
Document ID
19950034548
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Porri, A.
(Center for Advanced Research in Space Optics Trieste, Italy)
Stalio, R.
(Center for Advanced Research in Space Optics Trieste, Italy)
Ali, B.
(Ohio State Univ. Columbus, OH, United States)
Polidan, R. S.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Morossi, C.
(Astronomical Observatory of Trieste Trieste, Italy)
Date Acquired
August 16, 2013
Publication Date
March 20, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 424
Issue: 1
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A66147
Distribution Limits
Public
Copyright
Other

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