Related papers: On the High--Velocity Ejecta of the Type Ia Supern…
As the first step in a comprehensive, comparative, direct analysis of the spectra of Type Ia supernovae (SNe Ia), we use the parameterized supernova synthetic-spectrum code, SYNOW, to interpret 26 spectra of the well-observed SN 1994D. Our…
Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared with observed photospheric-phase optical spectra of the normal Type Ic SN 1994I and the peculiar Type Ic SNe 1997ef and 1998bw. The…
Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared to observed photospheric-phase spectra of the Type Ic supernova 1994I. The observed optical spectra can be well matched by synthetic…
Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared to spectra of the unusual Type Ib supernova 2005bf. We confirm the discovery by Folatelli et al. (2006) that very early spectra (about…
Late-time spectra of Type Ia supernovae (SNe Ia) are important in clarifying the physics of their explosions, as they provide key clues to the inner structure of the exploding white dwarfs. We examined late-time optical spectra of 36 SNe…
In Type Ia Supernovae (\sneia), the relative abundances of chemical elements are affected by the neutron excess in the composition of the progenitor white dwarf. Since these products leave signatures in the spectra near maximum light,…
The late-time spectra of Type Ia supernovae (SNe Ia) are powerful probes of the underlying physics of their explosions. We investigate the late-time optical and near-infrared spectra of seven SNe Ia obtained at the VLT with XShooter at…
It has been widely accepted that Type Ia supernovae (SNe Ia) are thermonuclear explosions of a CO white dwarf. However, the natures of the progenitor system(s) and explosion mechanism(s) are still unclarified. Thanks to the recent…
A comparative study of spectra of 21 Type Ia supernovae (SNe Ia) obtained about one week before maximum light, and 8 spectra obtained 11 or more days before maximum, is presented. To a large extent the premaximum spectra exhibit the…
Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared to photospheric-phase spectra of Type Ib supernovae (SNe Ib). Although the synthetic spectra are based on many simplifying…
The Type Ia SN 2000cx exhibited multiple peculiarities, including a lopsided B-band light-curve peak that does not conform to current methods for using shapes of light curves to standardize SN Ia luminosities. We use the parameterized…
Spectral synthesis in 3-dimensional (3D) space for the earliest spectra of Type Ia supernovae (SNe Ia) is presented. In particular, the high velocity absorption features that are commonly seen at the earliest epochs ($\sim 10$ days before…
Evidence of high-velocity features such as those seen in the near-maximum spectra of some Type Ia Supernovae (eg SN 2000cx) has been searched for in the available SNIa spectra observed earlier than one week before B maximum. Recent…
Type Ia supernovae are the outcome of the explosion of a carbon-oxygen white dwarf in a close binary system. They are thought to be the main contributors to the galactic nucleosynthesis of iron-peak elements, with important contributions to…
We present photometric and spectroscopic observations of SN 2024gy, a Type Ia supernova (SN Ia) exhibiting high-velocity features (HVFs) in its early-time spectra. This SN reaches a peak $B$-band magnitude of $-19.25 \pm 0.29$ mag and…
We have calculated fast direct spectral model fits to two early-time spectra of the Type-II plateau SN 1999em, using the SYNOW synthetic spectrum code. The first is an extremely early blue optical spectrum and the second a combined HST and…
The properties of the highest velocity ejecta of normal Type Ia supernovae (SNe Ia) are studied via models of very early optical spectra of 6 SNe. At epochs earlier than 1 week before maximum, SNe with a rapidly evolving Si II 6355 line…
The ZTF SN Ia Data Release 2 provides a perfect opportunity to perform a thorough search for, and subsequent analysis of, high-velocity components in the Si II $\lambda$6355 feature in the pre-peak regime. The source of such features…
We present a preliminary analysis of an extensive set of optical observations of the Type Ia SN 2005hk. We show that the evolution of SN 2005hk closely follows that of the peculiar SN 2002cx. SN 2005hk is more luminous than SN 2002cx, while…
In spite of the apparent lack of Si II and S II features in its spectra, SN 2002cx was classified as a peculiar Type Ia supernova (SN Ia) on the basis of its overall photometric and spectroscopic behavior. Spectra obtained near maximum…