Detailed Spectral Analysis of the Type Ib Supernova 1999dn. Paper I: Hydrogen-free Models

Abstract

We present spectral fits to five epochs of the typical Type Ib supernova 1999dn using the generalized, non-LTE, stellar atmospheres code PHOENIX. Our goal is threefold: to determine basic physical properties of the supernova ejecta, such as velocity, temperature, and density gradients; to reproduce He I absorption lines by invoking non-thermal excitation; and, to investigate possible spectral signatures of hydrogen, especially a feature around 6200 Angstrom, which has been attributed to high velocity $H_{\alpha }$. Our models assume an atmosphere with uniform composition devoid of any hydrogen. Our model spectra fit the observed spectra well, successfully reproducing most of the features, including the prominent He I absorptions. The most plausible alternative to $H_{\alpha }$ as the source of the 6200 Angstrom feature is a blend of Fe II and Si II lines, which can be made stronger to fit the observed feature better by increasing the metallicity of the ejecta. High-metallicity models fit well at early epochs, but not as well as solar-metallicity models after maximum light. While this blend of metal lines is a reasonable explanation of the source of the 6200 Angstrom feature, it is still important to investigate hydrogen as the source; therefore, a second paper will present models that include a thin shell of hydrogen around the main composition structure.

arXiv comment24 pages, 11 figures, 2 tables, submitted to ApJ

References in corpus (14)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• How Massive Single Stars End their Life
• Parallel Implementation of the PHOENIX Generalized Stellar Atmosphere Program
• Optical Spectroscopy of Type Ib/c Supernovae
• Direct Analysis of Spectra of Type Ib Supernovae
• Hydrogen and helium traces in type Ib-c supernovae
• Parallel Implementation of the PHOENIX Generalized Stellar Atmosphere Program. II: Wavelength Parallelization
• The Effects of Fe II NLTE on Nova Atmospheres and Spectra
• The peculiar type Ib supernova 2005bf: explosion of a massive He star with a thin hydrogen envelope?
• Detailed NLTE Model Atmospheres for Novae during Outburst: I. New Theoretical Results
• Spectrum Analysis of the Type Ib Supernova 1999dn: Probable Identifications of C II and H-alpha
• Direct Analysis of Spectra of the Unusual Type Ib Supernova 2005bf
• Hydrogen in Type Ic Supernovae?
• Exceptionally Bright Type Ib Supernova 1991D

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