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Date and Time of the Query: 2019-06-25 T16:46:58 PDT
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For refcode 2012MNRAS.419.2783T:
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Copyright by Royal Astronomical Society. 2012MNRAS.419.2783T Measuring expansion velocities in Type II-P supernovae Takats, K.; Vinko, J. Abstract. We estimate photospheric velocities of Type II-P supernovae (SNe) using model spectra created with SYNOW, and compare the results with those obtained either by more conventional techniques, such as cross-correlation, or by measuring the absorption minimum of P Cygni features. Based on a sample of 81 observed spectra of five SNe, we show that SYNOW provides velocities that are similar to those obtained by more sophisticated non-local thermodynamic equilibrium modelling codes, but they can be derived in a less computation-intensive way. The estimated photospheric velocities ({nu}_model_) are compared to those measured from Doppler shifts of the absorption minima of the H{beta} and the Fe II{lambda}5169 features. Our results confirm that Fe II velocities (v_Fe_) have a tighter and more homogeneous correlation with the estimated photospheric velocities than those measured from H{beta}, but both suffer from phase-dependent systematic deviations. The same is true for a comparison with the cross-correlation velocities. We verify and improve the relations between v_Fe_, v_H{beta}_ and v_model_ in order to provide useful formulae for interpolating/extrapolating the velocity curves of Type II-P SNe to phases not covered by observations. We also discuss implications of our results for the distance measurements of Type II-P SNe and show that the application of the model velocities is preferred in the expanding photosphere method. Key words: supernovae: general, supernovae: individual: SN 1999em, supernovae: individual: SN 2004dj, supernovae: individual: SN 2004et, supernovae: individual: SN 2005cs, supernovae: individual: SN 2006bp
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