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Record 12 of 4044
Non-LTE model atmosphere analysis of Nova Cygni 1992
External Online Source: doi:10.1086/173775
Author and Affiliation:
Hauschildt, P. H.(Arizona State Univ., Tempe, AZ, United States)
Starrfield, S.(Arizona State Univ., Tempe, AZ, United States)
Austin, S.(Arizona State Univ., Tempe, AZ, United States)
Wagner, R. M.(Ohio State Univ., Columbus, OH, United States)
Shore, S. N.(NASA Goddard Space Flight Center, Greenbelt, MD, United States)
Sonneborn, G.(NASA Goddard Space Flight Center, Greenbelt, MD, United States)
Abstract: We use spherically symmetric non-local thermodynamic equilibrium (non-LTE), line-blanketed, expanding model atmospheres to analyze the International Ultraviolet Explorer (IUE) and optical spectra of Nova Cygni 1992 during the early phases of its outburst. We find that the first IUE spectrum obtained just after discovery on 1992 February 20, is best reproduced by a model atmosphere with a steep density gradient and homologous expansion, whereas the IUE and optical spectra obtained on February 24 show an extended, optically thick, wind structure. Therefore, we distinguish two phases of the early evolution of the nova photosphere: the initial, rapid, 'fireball' phase and the subsequent, much longer, optically thick 'wind' phase. The importance of line-blanketing in nova spectra is demonstrated. Our preliminary abundance analysis implies that hydrogen is depeleted in the ejecta, corresponding to abundance enhancements of Fe by a factor of approximately 2 and of CNO by more than a factor of 10 when compared to solar abundances. The synthetic spectra reproduce both the observed pseudo-continua as well as most of the observed features from the UV to the optical spectral range and demonstrate the importance of obtaining nearly simultaneous UV and optical spectra for performing accurate analyses of expanding stellar atmospheres (for both novae and supernovae).
Publication Date: Feb 20, 1994
Document ID:
19950036118
(Acquired Dec 28, 1995)
Accession Number: 95A67717
Subject Category: ASTROPHYSICS
Document Type: Journal Article
Publication Information: Astrophysical Journal, Part 1 (ISSN 0004-637X); 422; 2; p. 831-844
Publisher Information: United States
Financial Sponsor: NASA; United States
Organization Source: NASA Goddard Space Flight Center; Greenbelt, MD, United States
NASA; Washington, DC, United States
Description: 14p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: ASTRONOMICAL MODELS; ATMOSPHERIC MODELS; CATACLYSMIC VARIABLES; LINE SPECTRA; LOCAL THERMODYNAMIC EQUILIBRIUM; NOVAE; NUCLEAR EXPLOSIONS; STELLAR ATMOSPHERES; ULTRAVIOLET ASTRONOMY; ABUNDANCE; HYDROGEN; IRON; IUE; LIGHT (VISIBLE RADIATION); ULTRAVIOLET SPECTRA
Imprint And Other Notes: Astrophysical Journal, Part 1 vol. 422, no. 2 p. 831-844 February 20, 1994
Miscellaneous Notes: Research sponsored by NASA and NSF
Availability Source: Other Sources
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