Timmes, Brown, & Truran found that metallicity variations could theoretically account for a 25% variation in the mass of 56 Ni synthesized in Type Ia supernovae (SNe Ia), and thus account for a large fraction of the scatter in observed SN Ia luminosities. Higher-metallicity progenitors are more neutron-rich, producing more stable burning -2products relative to radioactive 56 Ni. We develop a new method for estimating bolometric luminosity and 56 Ni yield in SNe Ia and use it to test the theory with data from the Supernova Legacy Survey. We find that the average 56 Ni yield does drop in SNe Ia from high metallicity environments, but the theory can only account for 7%-10% of the dispersion in SN Ia 56 Ni mass, and thus luminosity. This is because the effect is dominant at metallicities significantly above solar, whereas we find that SN hosts have predominantly subsolar or only moderately above-solar metallicities. We also show that allowing for changes in O/Fe with the metallicity [Fe/H] does not have a major effect on the theoretical prediction of Timmes, Brown, & Truran, so long as one is using the O/H as the independent variable. Age may have a greater effect than metallicity -we find that the luminosity weighted age of the host galaxy is correlated with 56 Ni yield, and thus more massive progenitors give rise to more luminous explosions. This is hard to understand if most SNe Ia explode when the primaries reach the Chandrasekhar mass. Finally, we test the findings of Gallagher et al., that the residuals of SNe Ia from the Hubble diagram are correlated with host galaxy metallicity, and we find no such correlation.

We use three years of data from the Supernova Legacy Survey (SNLS) to study the general properties of core-collapse and type Ia supernovae. This is the first such study using the "rolling search" technique which guarantees well-sampled SNLS light curves and good efficiency for supernovae brighter than i ′ ∼ 24. Using host photometric redshifts, we measure the supernova absolute magnitude distribution down to luminosities 4.5 mag fainter than normal SNIa. Using spectroscopy and light-curve fitting to discriminate against SNIa, we find a sample of 117 core-collapse supernova candidates with redshifts z < 0.4 (median redshift of 0.29) and measure their rate to be larger than the type Ia supernova rate by a factor 4.5 ± 0.8(stat.) ± 0.6(sys.). This corresponds to a core-collapse rate at z = 0.3 of [1.42 ± 0.3(stat.) ± 0.3(sys.)] × 10 −4 yr −1 (h −1 70 Mpc) −3 .

We report the serendipitous detection by GALEX of fast (!1 day) rising (տ1 mag) UV emission from two Type II plateau (II-P) supernovae (SNe) at and 0.324 discovered by the Supernova Legacy Survey. Optical z p 0.185 photometry and VLT spectroscopy 2 weeks after the GALEX detections link the onset of UV emission to the time of shock breakout. Using radiation hydrodynamics and non-LTE radiative transfer simulations, and starting from a standard red supergiant (RSG; Type II-P SN progenitor) star evolved self-consistently from the main sequence to iron core collapse, we model the shock breakout phase and the 55 hr that follow. The small scale height of our RSG atmosphere model suggests that the breakout signature is a thermal soft X-ray burst ( ) with å l ∼ 90 A peak duration of Շ2000 s. Longer durations are possible but require either an extended and tenuous nonstandard envelope or an unusually dense RSG wind with yr Ϫ1 . The GALEX observations miss the peak of the luminous) UV burst but unambiguously capture the rise of the emission and a subsequent 2 day long plateau. M ≈ Ϫ20 FUVThe postbreakout, UV-bright plateau is a prediction of our model in which the shift of the peak of the spectral energy distribution (SED) from ∼100 to ∼1000 and the ejecta expansion both counteract the decrease in bolometric A luminosity from ∼10 11 to ∼10 9 over that period. Based on the observed detection efficiency of our study, we L , make predictions for the breakout detection rate of the GALEX Time Domain Survey.

Aims. We present 139 spectra of 124 Type Ia supernovae (SNe Ia) that were observed at the ESO/VLT during the first three years of the Canada-France-Hawaï Telescope (CFHT) supernova legacy survey (SNLS). This homogeneous data set is used to test for redshift evolution of SN Ia spectra, and will be used in the SNLS 3rd year cosmological analyses. Methods. Spectra have been reduced and extracted with a dedicated pipeline that uses photometric information from deep CFHT legacy survey (CFHT-LS) reference images to trace, at sub-pixel accuracy, the position of the supernova on the spectrogram as a function of wavelength. It also separates the supernova and its host light in ∼60% of cases. The identification of the supernova candidates is performed using a spectrophotometric SN Ia model. Results. A total of 124 SNe Ia, roughly 50% of the overall SNLS spectroscopic sample, have been identified using the ESO/VLT during the first three years of the survey. Their redshifts range from z = 0.149 to z = 1.031. The average redshift of the sample is z = 0.63 ± 0.02. This constitutes the largest SN Ia spectral set to date in this redshift range. The spectra are presented along with their best-fit spectral SN Ia model and a host model where relevant. In the latter case, a host subtracted spectrum is also presented. We produce average spectra for pre-maximum, maximum and post-maximum epochs for both z < 0.5 and z ≥ 0.5 SNe Ia. We find that z < 0.5 spectra have deeper intermediate mass element absorptions than z ≥ 0.5 spectra. The differences with redshift are consistent with the selection of brighter and bluer supernovae at higher redshift.