Supernovae, Iron nucleosynthesis and the Universe as Quran

Reviews of Modern Physics, 1997

Forty years ago Burbidge, Burbidge, Fowler, and Hoyle combined what we would now call fragmentary evidence from nuclear physics, stellar evolution and the abundances of elements and isotopes in the solar system as well as a few stars into a synthesis of remarkable ingenuity. Their review provided a foundation for forty years of research in all of the aspects of low energy nuclear experiments and theory, stellar modeling over a wide range of mass and composition, and abundance studies of many hundreds of stars, many of which have shown distinct evidence of the processes suggested by B 2 FH. In this review we summarize progress in each of these fields with emphasis on the most recent developments. [S0034-6861(97)00204-3]

TURKISH JOURNAL OF PHYSICS

For decades large-scale cosmic structures have been modeled as the gravitational amplification of small-density perturbations of the cosmological recombination epoch of the Big Bang. In astrophysics, cosmological nucleosynthesis is considered responsible for the production of the pristine gas, which should be found in the first-generation stars in the form of hydrogen and helium as the main constituents. In the later type of second-generation stars, hydrogen is converted into helium by the CN-cycle reactions, in which heavier elements are produced. These elements are believed to enrich the intergalactic medium by possible star bursts at the last stages of evolution. Stability criteria in the stellar evolutionary models pointed out that first-generation stars should be massive and live long enough for the nucleosynthesis of the natural elements, heavier than hydrogen and helium. Initially, they were expected to be very faint and blue to be observed spectroscopically. Nowadays, more and more metal-deficient star observations, made possible by the new era of space telescopes, are interpreted as the discovery of a primordial footprint of the initially pure gas. These new data are combined with the astrophysical models to review the predictability, mass, and chemical composition with regard to stability and existence of the first-generation stars.

The Astrophysical Journal, 2014

We investigate the origin of carbon-enhanced metal-poor (CEMP) stars starting from the recently discovered $\rm [Fe/H]<-7.1$ star SMSS J031300 (Keller et al. 2014). We show that the elemental abundances observed on the surface of SMSS J031300 can be well fit by the yields of faint, metal free, supernovae. Using properly calibrated faint supernova explosion models, we study, for the first time, the formation of dust grains in such carbon-rich, iron-poor supernova ejecta. Calculations are performed assuming both unmixed and uniformly mixed ejecta and taking into account the partial destruction by the supernova reverse shock. We find that, due to the paucity of refractory elements beside carbon, amorphous carbon is the only grain species to form, with carbon condensation efficiencies that range between (0.15-0.84), resulting in dust yields in the range (0.025-2.25)M$_{\odot}$. We follow the collapse and fragmentation of a star forming cloud enriched by the products of these faint supernova explosions and we explore the role played by fine structure line cooling and dust cooling. We show that even if grain growth during the collapse has a minor effect of the dust-to-gas ratio, due to C depletion into CO molecules at an early stage of the collapse, the formation of CEMP low-mass stars, such as SMSS J031300, could be triggered by dust cooling and fragmentation. A comparison between model predictions and observations of a sample of C-normal and C-rich metal-poor stars supports the idea that a single common pathway may be responsible for the formation of the first low-mass stars.

2021

Dr Priya Hasan is an Asst Professor in Physics at the Maulana Azad National Urdu University, Hyderabad. Her research interests are in observational astronomy, star formation, star clusters and galaxies. She is actively involved in olympiads, public outreach and science popularization programs. She is a member of the Astronomical Society of India Public Outreach & Education Committee (2016-2019) This article will briefly review the theory of star formation (SF) and its development using observations. This is very relevant in the present context since planet formation appears to be a byproduct of SF, and the whole question of life in the universe and its origin can be viewed with a new perspective.

Mass-fractionation enriches light elements and the lighter isotopes of each element at the solar surface, making a photosphere that is 91% H and 9% He. However, the solar interior consists mostly of elements that comprise 99% of ordinary meteorites -Fe, O, Ni, Si, S, Mg and Ca -elements made in the deep interior of a supernova. Solar energy arises from a series of nuclear reactions triggered by neutron-emission from the collapsed supernova core on which the Sun formed. Solar mass-fractionation, solar neutrinos, and an annual outpouring of 3 x 10 43 H atoms in the solar wind are by-products of solar luminosity.

Planets, Stars and Stellar Systems, 2013

Metal-poor stars hold the key to our understanding of the origin of the elements and the chemical evolution of the Universe. This chapter describes the process of discovery of these rare stars, the manner in which their surface abundances (produced in supernovae and other evolved stars) are determined from the analysis of their spectra, and the interpretation of their abundance patterns to elucidate questions of origin and evolution. More generally, studies of these stars contribute to other fundamental areas that include nuclear astrophysics, conditions at the earliest times, the nature of the first stars, and the formation and evolution of galaxies-including our own Milky Way. We illustrate this with results from studies of lithium formed during the Big Bang; of stars dated to within ∼1 Gyr of that event; of the most metal-poor stars, with abundance signatures very different from all other stars; and of the build-up of the elements over the first several Gyr. The combination of abundance and kinematic signatures constrains how the Milky Way formed, while recent discoveries of extremely metal-poor stars in the Milky Way's dwarf galaxy satellites constrain the hierarchical build-up of its stellar halo from small dark-matter dominated systems. We discuss two areas needing priority consideration. The first is improvement of abundance analysis techniques. While one-dimensional, Local Thermodynamic Equilibrium (1D/LTE) model atmospheres provide a mature and precise formalism, proponents of more physically realistic 3D/non-LTE techniques argue that 1D/LTE results are not accurate, with systematic errors often of order ∼0.5 dex or even more in some cases. Self-consistent 3D/non-LTE analysis as a standard tool is essential for meaningful comparison between the abundances of metal-poor stars and models of chemical enrichment. The second need is for larger samples of metal-poor stars, in particular those with [Fe/H] <-4 and those at large distances (20 − 50 kpc), including the Galaxy's ultra-faint dwarf satellites. With future astronomical surveys and facilities these endeavors will become possible. This will provide new insights into small-scale details of nucleosynthesis as well as large-scale issues such as galactic formation. Subject headings: Galaxy: formation − Galaxy: halo − stars: abundances − early Universe − nuclear reactions, nucleosynthesis, abundances 1.2.3. Nomenclature Chemical abundance is one of the basic parameters that define stellar populations, to which we shall return in Section 2.1. Here we define terms that we shall use in the present work. Baade (1944), in his seminal paper on the subject, defined two groups of stars, Type I and Type II, which today are referred to as Population I and

The Astrophysical Journal, 2010

The inclusion of rotationally-induced mixing in stellar evolution can alter the structure and composition of presupernova stars. We survey the effects of progenitor rotation on nucleosynthetic yields in Population III and II supernovae using the new adaptive mesh refinement (AMR) code CASTRO. We examine piston-driven spherical explosions in 15, 25 and 40 M ⊙ stars at Z = 0 and 10 −4 Z ⊙ with three explosion energies and two rotation rates. Rotation in the Z = 0 models resulted in primary nitrogen production and a stronger hydrogen burning shell which led all models to die as red supergiants (in contrast to the blue supergiant progenitors made without rotation). On the other hand, the Z = 10 −4 Z ⊙ models that included rotation ended their lives as compact blue stars. Because of their extended structure, the hydrodynamics favors more mixing and less fallback in the metal free stars than the Z = 10 −4 models. As expected, higher energy explosions produce more enrichment and less fallback than do lower energy explosions, and at constant explosion energy, less massive stars produce more enrichment and leave behind smaller remnants than do more massive stars. We compare our nucleosynthetic yields to the chemical abundances in the three most iron-poor stars yet found and reproduce the abundance pattern of one, HE 0557-4840, with a zero metallicity 15 M ⊙ , 2.4 × 10 51 erg supernova. A Salpeter IMF averaged integration of our yields for Z = 0 models with explosion energies of 2.4 × 10 51 ergs or less is in good agreement with the abundances observed in larger samples of extremely metal-poor stars, provided 15 M ⊙ stars are included. Since the abundance patterns of extremely metal-poor stars likely arise from a representative sample of progenitors, our yields suggest that 15-40 M ⊙ core-collapse supernovae with moderate explosion energies contributed the bulk of the metals to the early universe.

The Astrophysical Journal, 2010

The evolution and explosion of metal-free stars with masses 10 − 100 M ⊙ are followed, and their nucleosynthetic yields, light curves, and remnant masses determined. Such stars would have been the first to form after the Big Bang and may have left a distinctive imprint on the composition of the early universe. When the supernova yields are integrated over a Salpeter initial mass function (IMF), the resulting elemental abundance pattern is qualitatively solar, but with marked deficiencies of odd-Z elements with 7 ≤ Z ≤ 13. Neglecting the contribution of the neutrino wind from the neutron stars that they make, no appreciable abundances are made for elements heavier than germanium. The computed pattern compares favorably with what has been observed in metal-deficient stars with [Z] −3. The amount of ionizing radiation from this generation of stars is ∼ 2.16 MeV per baryon (4.15 B per M ⊙ ; where 1 B = 1 Bethe = 10 51 erg) for a Salpeter IMF, and may have played a role in reionizing the universe. Most of the stars end their lives as blue supergiants and make supernovae with distinctive light curves resembling SN 1987A, but some produce primary nitrogen by dredge up and become red supergiants. These make brighter supernovae like typical Type IIp's. For the lower mass supernovae considered, the distribution of remnant masses clusters around typical modern neutron star masses, but above 20 M ⊙ to 30 M ⊙ , with the value depending on explosion energy, black holes are copiously formed by fallback, with a maximum hole mass of ∼ 40 M ⊙. A novel automated fitting algorithm is developed for determining optimal combinations of explosion energy, mixing, and initial mass function in the large model data base to agree with specified data sets. The model is applied to the low metallicity sample of Cayrel et al. (2004) and the two ultra-iron-poor stars HE0107-5240 and HE1327-2326. Best agreement with these low metallicity stars is achieved with very little mixing, and none of the metal-deficient data sets considered show the need for a high energy explosion component. To the contrary, explosion energies somewhat less than 1.2 B seem to be preferred in most cases.

2009

The inclusion of rotationally-induced mixing in stellar evolution can alter the structure and composition of presupernova stars. We survey the effects of progenitor rotation on nucleosynthetic yields in Population III and II supernovae using the new adaptive mesh refinement (AMR) code CASTRO. We examine piston-driven spherical explosions in 15, 25 and 40 M ⊙ stars at Z = 0 and 10 −4 Z ⊙ with three explosion energies and two rotation rates. Rotation in the Z = 0 models resulted in primary nitrogen production and a stronger hydrogen burning shell which led all models to die as red supergiants (in contrast to the blue supergiant progenitors made without rotation). On the other hand, the Z = 10 −4 Z ⊙ models that included rotation ended their lives as compact blue stars. Because of their extended structure, the hydrodynamics favors more mixing and less fallback in the metal free stars than the Z = 10 −4 models. As expected, higher energy explosions produce more enrichment and less fallback than do lower energy explosions, and at constant explosion energy, less massive stars produce more enrichment and leave behind smaller remnants than do more massive stars. We compare our nucleosynthetic yields to the chemical abundances in the three most iron-poor stars yet found and reproduce the abundance pattern of one, HE 0557-4840, with a zero metallicity 15 M ⊙ , 2.4 × 10 51 erg supernova. A Salpeter IMF averaged integration of our yields for Z = 0 models with explosion energies of 2.4 × 10 51 ergs or less is in good agreement with the abundances observed in larger samples of extremely metal-poor stars, provided 15 M ⊙ stars are included. Since the abundance patterns of extremely metal-poor stars likely arise from a representative sample of progenitors, our yields suggest that 15-40 M ⊙ core-collapse supernovae with moderate explosion energies contributed the bulk of the metals to the early universe.

Nature, 2015