arXiv subjects

S. Valenti

Publications and source records attributed to S. Valenti.

183 records · Page 11Linked to original sources

arXiv2006

The properties of the "standard" type Ic supernova 1994I from spectral models

The properties of the type Ic supernova SN 1994I are re-investigated. This object is often referred to as a "standard SN Ic" although it exhibited an extremely fast light curve and unusually blue early-time spectra. In addition, the observations were affected by significant dust extinction. A series of spectral models are computed based on the explosion model CO21 (Iwamoto et al. 1994) using a Monte Carlo transport spectral synthesis code. Overall the density structure and abundances of the explosion model are able to reproduce the photospheric spectra well. Reddening is estimated to be E(B-V)=0.30 mag, a lower value than previously proposed. A model of the nebular spectrum of SN 1994I points toward a slightly larger ejecta mass than that of CO21. The photospheric spectra show a large abundance of iron-group elements at early epochs, indicating that mixing within the ejecta must have been significant. We present an improved light curve model which also requires the presence of 56Ni in the outer layers of the ejecta.

astro-ph↗

arXiv2005

SN/GRB connection: a statistical approach with BATSE and Asiago Catalogues

Recent observations suggest that some types of GRB are physically connected with SNe of type Ib/c. However, it has been pointed out by several authors that some GRBs could be associated also with other types of core-collapse SNe (type IIdw/IIn). On the basis of a comphrensive statistical study, which has made use of the BATSE and Asiago catalogues, we have found that: i) the temporal and spacial distribution of SNe-Ib/c is marginally correlated with that of the BATSE GRBs; ii) we do not confirm the existence of an association between GRBs and SNe-IIdw/IIn.

astro-ph↗

arXiv2004

Death rate of massive stars at redshift ~0.3

We report the first result of a supernova search program designed to measure the evolution of the supernova rate with redshift. To make the comparison with local rates more significant we copied, as much as possible, the same computation recepies as for the measurements of local rates. Moreover, we exploited the multicolor images and the photometric redshift technique to characterize the galaxy sample and accurately estimate the detection efficiency. Combining our data with the recently published meaurements of the SN Ia rate at different redshifts, we derived the first, direct measurement of the core collapse supernova rate at z = 0.26 as r_cc = 1.45^{+0.55}{-0.45} h^2 SNu [h=H_0/75]. This is a factor three {+/- 50%)} larger than the local estimate. The increase for a look back time of "only" 2.8 Gyr is more rapid than predicted by most of the published models of the SN rate evolution. Core-collapse SN rates measure the death rate of massive star and, because of the short time scale of evolution, can be translated in a measurement of the ongoing SFR. Assuming a Salpeter IMF and the standard scenario for core-collapse progenitors we derived to an estimate of the star formation rate at redshift 3.1^{+1.1}{-1.0} 10^-2 h^3 M_sun yr^-1 Mpc^{-3} which compare very well with a recent estimate based on the measurement of the Halpha luminosity density at the same redshift.

astro-ph↗