966 research outputs found
Presupernova evolution and explosive nucleosynthesis of zero metal massive stars
We present a new set of zero metallicity models in the range 13-80 together to the associated explosive nucleosynthesis. These models are
fully homogeneous with the solar metallicity set we published in Limongi &
Chieffi (2006) and will be freely available at the web site
http://www.iasf-roma.inaf.it./orfeo/public{\_}html. A comparison between these
yields and an average star that represents the average behavior of most of the
very metal poor stars in the range confirms previous
findings that only a fraction of the elemental [X/Fe] may be fitted by the
ejecta of core collapse supernovae.Comment: 39 pages, 8 figures, 2 tables, accepted for publication in ApJ
The metal and dust yields of the first massive stars
We quantify the role of Population (Pop) III core-collapse supernovae (SNe)
as the first cosmic dust polluters. Starting from a homogeneous set of stellar
progenitors with masses in the range [13 - 80] Msun, we find that the mass and
composition of newly formed dust depend on the mixing efficiency of the ejecta
and the degree of fallback experienced during the explosion. For standard Pop
III SNe, whose explosions are calibrated to reproduce the average elemental
abundances of Galactic halo stars with [Fe/H] < -2.5, between 0.18 and 3.1 Msun
(0.39 - 1.76 Msun) of dust can form in uniformly mixed (unmixed) ejecta, and
the dominant grain species are silicates. We also investigate dust formation in
the ejecta of faint Pop III SN, where the ejecta experience a strong fallback.
By examining a set of models, tailored to minimize the scatter with the
abundances of carbon-enhanced Galactic halo stars with [Fe/H ] < -4, we find
that amorphous carbon is the only grain species that forms, with masses in the
range 2.7 10^{-3} - 0.27 Msun (7.5 10^{-4} - 0.11 Msun) for uniformly mixed
(unmixed) ejecta models. Finally, for all the models we estimate the amount and
composition of dust that survives the passage of the reverse shock, and find
that, depending on circumstellar medium densities, between 3 and 50% (10 - 80%)
of dust produced by standard (faint) Pop III SNe can contribute to early dust
enrichment.Comment: Accepted by MNRAS, 22 pages, 12 figures, 12 table
Evolution, Explosion and Nucleosynthesis of Core Collapse Supernovae
We present a new set of presupernova evolutions and explosive yields of
massive stars of initial solar composition (Y=0.285, Z=0.02) in the mass range
13-35 Msun. All the models have been computed with the latest version (4.97) of
the FRANEC code that now includes a nuclear network extending from neutrons to
Mo98. The explosive nucleosynthesis has been computed twice: a first one with
an hydro code and a second one following the simpler radiation dominated shock
approximation (RDA).Comment: 20 pages, 10 figures, 12 tables. Accepted for publication on Ap
Hot Cores : Probes of High-Redshift Galaxies
The very high rates of second generation star formation detected and inferred
in high redshift objects should be accompanied by intense millimetre-wave
emission from hot core molecules. We calculate the molecular abundances likely
to arise in hot cores associated with massive star formation at high redshift,
using several independent models of metallicity in the early Universe. If the
number of hot cores exceeds that in the Milky Way Galaxy by a factor of at
least one thousand, then a wide range of molecules in high redshift hot cores
should have detectable emission. It should be possible to distinguish between
independent models for the production of metals and hence hot core molecules
should be useful probes of star formation at high redshift.Comment: Updated to correspond to version accepted by MNRA
On the Origin of the Early Solar System Radioactivities. Problems with the AGB and Massive Star Scenarios
Recent improvements in stellar models for intermediate-mass and massive stars
are recalled, together with their expectations for the synthesis of radioactive
nuclei of lifetime Myr, in order to re-examine the origins
of now extinct radioactivities, which were alive in the solar nebula. The
Galactic inheritance broadly explains most of them, especially if -process
nuclei are produced by neutron star merging according to recent models.
Instead, Al, Ca, Cs and possibly Fe require
nucleosynthesis events close to the solar formation. We outline the persisting
difficulties to account for these nuclei by Intermediate Mass Stars (2
M/M). Models of their final stages now
predict the ubiquitous formation of a C reservoir as a neutron capture
source; hence, even in presence of Al production from Deep Mixing or Hot
Bottom Burning, the ratio Al/Pd remains incompatible with
measured data, with a large excess in Pd. This is shown for two recent
approaches to Deep Mixing. Even a late contamination by a Massive Star meets
problems. In fact, inhomogeneous addition of Supernova debris predicts
non-measured excesses on stable isotopes. Revisions invoking specific low-mass
supernovae and/or the sequential contamination of the pre-solar molecular cloud
might be affected by similar problems, although our conclusions here are
weakened by our schematic approach to the addition of SN ejecta. The limited
parameter space remaining to be explored for solving this puzzle is discussed.Comment: Accepted for publication on Ap
Chemical evolution with rotating massive star yields II. A new assessment of the solar s- and r- process components
The decomposition of the Solar system abundances of heavy isotopes into their sand r- components plays a key role in our understanding of the corresponding nuclear
processes and the physics and evolution of their astrophysical sites. We present a new
method for determining the s- and r- components of the Solar system abundances,
fully consistent with our current understanding of stellar nucleosynthesis and galactic chemical evolution. The method is based on a study of the evolution of the solar
neighborhood with a state-of-the-art 1-zone model, using recent yields of low and intermediate mass stars as well as of massive rotating stars. We compare our results with
previous studies and we provide tables with the isotopic and elemental contributions
of the s- and r-processes to the Solar system compositionThis article is based upon work partially supported from
the “ChETEC” COST Action (CA16117) of COST (European Cooperation in Science and Technology). C.A. acknowledges in part to the Spanish grants AYA2015-63588-P
and PGC2018-095317-B-C21 within the European Founds
for Regional Development (FEDER)
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