Claes Fransson

Early and late time VLT spectroscopy of SN 2001el - progenitor constraints for a type Ia supernova

We present early time high-resolution (VLT/UVES) and late time low-resolution (VLT/FORS) optical spectra of the normal typexa0Ia supernova, SNxa02001el. The high-resolution spectra were obtainedxa09 and 2xa0days before ( B -band) maximum light. This was in order to allow the detection of narrow hydrogen and/or helium emission lines from the circumstellar medium of the supernova. No such lines were detected in our data. We therefore use these spectra together with photoionisation models to derive upper limits of

Three-dimensional modeling of type Ia supernovae – The power of late time spectra

9times10^{-6} ~{M}_odot~{rm yr}^{-1}

On the afterglow of the x-ray flash of 2003 July 23: photometric evidence for an off-axis gamma-ray burst with an associated supernova?

and

The 44Ti-powered spectrum of SN 1987A

5times10^{-5} ~{M}_odot~{rm yr}^{-1}

Supernova 1998bw - The final phases ⋆

for the mass loss rate from the progenitor system of SNxa02001el assuming velocities of 10 xa0kmxa0s -1 xa0and 50 xa0kmxa0s -1 , respectively, for a wind extending to outside at least a few

Optical and near infrared observations of SN 1998bu

times 10^{15}

ISO/SWS observations of SN 1987A - II. A refined upper limit on the mass of

cm away from the supernova explosion site. So far, these are the best H α based upper limits obtained for a type Ia supernova, and exclude a symbiotic star in the upper mass loss rate regime (so called Mira type stars) from being the progenitor of SNxa02001el. The low-resolution spectrum was obtained in the nebular phase of the supernova, ~400xa0days after the maximum light, to search for any hydrogen rich gas originating from the supernova progenitor system. However, we see no signs of Balmer lines in our spectrum. Therefore, we model the late time spectra to derive an upper limit of ~0.03xa0

^\mathsf{44}

M_{odot}

Ti in the ejecta of SN 1987A

for solar abundance material present at velocities lower than 1000xa0xa0kmxa0s -1 xa0within the supernova explosion site. According to numerical simulations of Marietta etxa0al. (2000) this is less than the expected mass lost by a subgiant, red giant or a main-sequence secondary star at a small binary separation as a result of the SN explosion. Our data therefore exclude these scenarios as the progenitor of SN 2001el. Finally, we discuss the origin of high velocity Caxa0II lines previously observed in a few type Ia supernovae before the maximum light. We see both the Caxa0II IR triplet and the H&K lines in our earliest (-9xa0days) spectrum at a very high velocity of up to ~34xa0000 kmxa0s -1 . The spectrum also shows a flat-bottomed Sixa0II “6150xa0A” feature similar to the one previously observed in SNxa01990N (Leibundgut etxa0al. 1991, ApJ, 371, L23) at 14 days before maximum light. We compare these spectral features in SNxa02001el to those observed in SNxa01984A and SNxa01990N at even higher velocities.

The discovery and classification of 16 supernovae at high redshifts in ELAIS-S1 - The Stockholm VIMOS Supernova Survey II

Late time synthetic spectra of typexa0Iaxa0supernovae, based on three-dimensional deflagration models, are presented. We mainly focus on one model, “c3_3d_256_10s”, for which the hydrodynamics (Ropke 2005, A&A, 432, 969) and nucleosynthesis (Travaglio etxa0al. 2004, A&A, 425, 1029) was calculated up to the homologous phase of the explosion. Other models with different ignition conditions and different resolution are also briefly discussed. The synthetic spectra are compared to observed late time spectra. We find that while the model spectra afterxa0300 to 500xa0days show a good agreement with the observed Fexa0II-IIIxa0features, they also show too strong Oxa0I and Cxa0Ixa0lines compared to the observed late time spectra. The oxygen and carbon emission originates from the low-velocity unburned material in the central regions of these models. To get agreement between the models and observations we find that only a small mass of unburned material may be left in the center after the explosion. This may be a problem for pure deflagration models, although improved initial conditions, as well as higher resolution decrease the discrepancy. The relative intensity from the different ionization stages of iron is sensitive to the density of the emitting iron-rich material. We find that clumping, with the presence of low density regions, is needed to reproduce the observed iron emission, especially in the range betweenxa04000 and 6000xa0A. Both temperature and ionization depend sensitively on density, abundances and radioactive content. This work therefore illustrates the importance of including the inhomogeneous nature of realistic three-dimensional explosion models. We briefly discuss the implications of the spectral modeling for the nature of the explosion.