Calibrating hydrogen-rich core-collapse supernovae for their use as distance indicators independently of type Ia supernovae

Using our new general-relativistic, radiation hydrodynamics, Lagrangian code, we computed a rather extended grid of hydrogen-rich core-collapse supernova (CC-SN) models and explored the potentials of their "standardization" as distance indicators. We discuss the properties of some calibrations previously reported in the literature and present new correlations based on the behavior of the light curve, that can be employed for calibrating hydrogen-rich CC-SNe using only photometric data.Comment: 2 pages, 3 figures, to appear in Proceedings of IAU Symp. 281, Binary Paths to Type Ia Supernovae Explosions, ed. R. Di Stefano and M. Ori

The s-process nucleosynthesis in massive stars: current status and uncertainties due to convective overshooting

Context: It is well known that the so-called s-process is responsible for the production of neutron-rich trans-iron elements, that form the bulk of the "heavy nuclides" (i.e. nuclides more massive than the iron-group nuclei) in the solar-system composition, considered as "standard of reference" dataset for cosmic abundances. In particular, the s-process produces about half of all the trans-iron isotopes by moving along the "valley of stability" through a series of neutron capture reactions and beta decays. More than one s-process "component" (i.e. a nucleosynthesis event with a single set of physical conditions like neutron exposure, initial abundances and neutron density) is required in order to explain the observed solar distribution of s-nuclei abundances. Current views on the subject suggest the existence of several components that, in terms of stellar environments, correspond to distinct categories of stars in different evolutionary phases. Aims: The purpose of the chapter is to review the s-process nucleosynthesis occurring in massive stars (so-called weak component of s-process), pointing particular attention on the recent studies devoted to analyze how the uncertainties due to stellar evolution modeling and, specifically, due to convective overshooting affect the efficiency of this nucleosynthesis process.Comment: 20 pages, 7 figures, invited chapter accepted for publication in the book "Astrophysics" (ISBN 979-953-307-389-6) - Book editor: Ibrahim Kucuk - InTech (some text added in the acknowledgements, typos corrected

Supernova 1987A: a Template to Link Supernovae to their Remnants

The emission of supernova remnants reflects the properties of both the progenitor supernovae and the surrounding environment. The complex morphology of the remnants, however, hampers the disentanglement of the two contributions. Here we aim at identifying the imprint of SN 1987A on the X-ray emission of its remnant and at constraining the structure of the environment surrounding the supernova. We performed high-resolution hydrodynamic simulations describing SN 1987A soon after the core-collapse and the following three-dimensional expansion of its remnant between days 1 and 15000 after the supernova. We demonstrated that the physical model reproducing the main observables of SN 1987A during the first 250 days of evolution reproduces also the X-ray emission of the subsequent expanding remnant, thus bridging the gap between supernovae and supernova remnants. By comparing model results with observations, we constrained the explosion energy in the range $1.2-1.4\times 10^{51}$~erg and the envelope mass in the range $15-17 M_{\odot}$. We found that the shape of X-ray lightcurves and spectra at early epochs (<15 years) reflects the structure of outer ejecta: our model reproduces the observations if the outermost ejecta have a post-explosion radial profile of density approximated by a power law with index $\alpha = -8$. At later epochs, the shapes of X-ray lightcurves and spectra reflect the density structure of the nebula around SN 1987A. This enabled us to ascertain the origin of the multi-thermal X-ray emission, to disentangle the imprint of the supernova on the remnant emission from the effects of the remnant interaction with the environment, and to constrain the pre-supernova structure of the nebula.Comment: 16 pages, 11 Figures; accepted for publication on Ap

Convective overshooting and production of s-nuclei in massive stars during their core He-burning phase

With the "post-processing" technique we explore the role of the convective overshooting on the production of s-nuclei in stellar models of different initial mass and metallicity ($15 \leq M_{ZAMS}/M_{\odot} \leq 25$; $10^{-4} \leq Z \leq 0.02$), considering a range of values for the parameter $f$, which determines the overall efficiency of convective overshooting.We find enhancements in the production of s-nuclei until a factor $\sim 6$ (measured as the average overproduction factor of the 6 s-only nuclear species with $60\lesssim A\lesssim90$) in all our models of different initial mass and metallicity with $f$ in the range $0.01{-}0.035$ (i.e. models with overshooting) compared to the production obtained with "no-overshooting" models (i.e. models with the same initial mass and metallicity, but $f=10^{-5}$). Moreover the results indicate that the link between the overshooting parameter $f$ and the s-process efficiency is essentially monotonic in all our models of different initial mass and metallicity. Also evident is the higher s-process efficiency when we progressively increase for a given f value both the mass of the models from 15 M$_\odot$ to 25 M$_\odot$ and the Z value from 10$^{-4}$ to 0.02. We also briefly discuss the possible consequences of these results for some open questions linked to the s-process weak component efficiency, as well as a "rule of thumb" to evaluate the impact of the convective overshooting on the yields of a generation of stars.Comment: 12 pages, 6 figures, A&A accepted (corrected typos plus minor changes in order to fulfill the guidelines for A&A manuscripts