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Date and Time of the Query: 2019-06-17 T21:10:02 PDT
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For refcode 1993A&A...269..423M:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1993A&A...269..423M Models for the early-time spectral evolution of the `standard' type Ia supernova 1990 N P.A. Mazzali, LB. Lucy, I.J. Danziger, C. Gouiffes, E. Cappellaro and M. Turatto European Southern Observatory Karl-Schwarzschildstr 2, W-8046 Garching bei Munchen. F.R. Germany ST-ECF, Karl-Schwarzschildstr 2, W-8046 Garching bei Munchen, F.R. Germany Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy Received May 19, accepted August 2, 1992 Abstract. A Monte Carlo spectrum synthesis code is used to model a series of spectra of the type Ia SN 1990 N covering the period from two weeks before (corresponding to 6 days after outburst) to two weeks after maximum. This represents almost the entire period when the supernova was in the photospheric epoch. A rescaled W7 density structure and a mixed W7 composition were adopted, while the temperature structure in the expanding supernova envelope was determined assuming radiative equilibrium, and the level occupation numbers in the envelope were obtained with a method that takes into account the main sources of departure from LTE. With these assumptions good fits were obtained for the 5 optical spectra covering the evolution of SN1990 N with time steps of approximately one week. The fits yield useful information on several parameters such as luminosity, velocity and temperature, and show that SN1990 N can be regarded as a prototypical SN Ia, the first of this kind for which complete coverage of the spectral evolution in the photospheric epoch has been obtained with modern detector technology. A nearly complete identification of the spectral lines giving rise to the observed features is offered, and uncertainties in the model predictions due to abundance or NLTE effects are discussed. Spectral evidence for the presence of nickel and cobalt in the amounts predicted by the explosion models is found to be not conclusive, in particular at the latest epoch studied. A theoretical light curve obtained from the model fits is also presented and implications on the distances obtained using SNe Ia as standard candles are discussed. Key words: supernovae: individual (SN 1990 N) - lines: formation - lines: identification - stars: abundances - distance scale
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