Does the structure of Population III supernova ejecta affect the elemental abundance of extremely metal-poor stars?

ABSTRACT The first generation of metal-free (Population III) stars are crucial for the production of heavy elements in the earliest phase of structure formation. Their mass scale can be derived from the elemental abundance pattern of extremely metal-poor (EMP) stars, which are assumed to inherit the abundances of uniformly mixed supernova (SN) ejecta. If the expanding ejecta maintains its initial stratified structure, the elemental abundance pattern of EMP stars might be different from that from uniform ejecta. In this work, we perform numerical simulations of the metal enrichment from stratified ejecta for normal core-collapse SNe (CCSNe) with a progenitor mass $25 \ {\rm M_{\bigodot }}$ and explosion energies 0.7–10 B ($1 \ {\rm B} = 10^{51} \ \rm erg$). We find that SN shells fall back into the central minihalo in all models. In the recollapsing clouds, the abundance ratio [M/Fe] for stratified ejecta is different from the one for uniform ejecta only within ±0.4 dex for any element M. We also find that, for the largest explosion energy (10 B), a neighbouring halo is also enriched. Only the outer layers containing Ca or lighter elements reach the halo, where [C/Fe] = 1.49. This means that C-enhanced metal-poor stars can form from the CCSN even with an average abundance ratio [C/Fe] = −0.65.

Seeding the second star – II. CEMP star formation enriched from faint supernovae

ABSTRACT Carbon-enhanced metal-poor (CEMP) stars are the living fossils holding records of chemical enrichment from early generations of stars. In this work, we perform a set of numerical simulations of the enrichment from a supernova (SN) of a first generation of metal-free (Pop III) star and the gravitational collapse of the enriched cloud, considering all relevant cooling/heating processes and chemical reactions as well as the growth of dust grains. We adopt faint SN models for the first time with progenitor masses MPopIII = 13–$80 \ {\rm M_{\bigodot }}$, which yield C-enhanced abundance patterns ([C/Fe] = 4.57–4.75) through mixing and fallback of innermost layers of the ejecta. This model also considers the formation and destruction of dust grains. We find that the metals ejected by the SN can be partly re-accreted by the same dark matter minihalo, and carbon abundance of the enriched cloud A(C) = 3.80–5.06 is lower than the abundance range of observed CEMP stars (A(C) ≳ 6) because the mass of the metals ejected by faint SNe is smaller than normal core-collapse SNe due to extensive fallback. We also find that cloud fragmentation is induced by gas cooling from carbonaceous grains for $M_{\rm Pop III}= 13 \ {\rm M_{\bigodot }}$ even with the lowest iron abundance [Fe/H] ∼ −9. This leads to the formation of low-mass stars, and these ‘giga metal-poor’ stars can survive until the present-day Universe and may be found by future observations.

Impact of uncertainties of unbound 10Li on the ground state of two-neutron halo 11Li

Recently, the energy spectrum of \boldsymbol{^{10}}10Li was measured upto \boldsymbol{4.6}4.6 MeV, via one-neutron transfer reaction \boldsymbol{d(^{9}\textrm{Li},~p)^{10}\textrm{Li}}𝐝(9Li,𝐩)10Li. Considering the ambiguities on the \boldsymbol{^{10}}10Li continuum spectrum with reference to new data, we report the configuration mixing in the ground state of the two-neutron halo nucleus \boldsymbol{^{11}}11Li for two different choices of the \boldsymbol{^{9}{\textrm{Li}}+n}9Li+𝐧 potential. For the present study, we employ a three-body (\boldsymbol{\textrm{core}+n+n}core+𝐧+𝐧) structure model developed for describing the two-neutron halo system by explicit coupling of unbound continuum states of the subsystem (\boldsymbol{\textrm{core}+n}core+𝐧), and discuss the two-neutron correlations in the ground state of \boldsymbol{^{11}}11Li.

On some classes of sublattices of the subgroup lattice

In this paper G always denotes a group. If K and H are subgroups of G, where K is a normal subgroup of H, then the factor group of H by K is called a section of G. Such a section is called normal, if K and H are normal subgroups of G, and trivial, if K and H are equal. We call any set S of normal sections of G a stratification of G, if S contains every trivial normal section of G, and we say that a stratification S of G is G-closed, if S contains every such a normal section of G, which is G-isomorphic to some normal section of G belonging S. Now let S be any G-closed stratification of G, and let L be the set of all subgroups A of G such that the factor group of V by W, where V is the normal closure of A in G and W is the normal core of A in G, belongs to S. In this paper we describe the conditions on S under which the set L is a sublattice of the lattice of all subgroups of G and we also discuss some applications of this sublattice in the theory of generalized finite T-groups.

On Finite Quasi-Core-p p-Groups

Given a positive integer n, a finite group G is called quasi-core-n if ⟨ x ⟩ / ⟨ x ⟩ G has order at most n for any element x in G, where ⟨ x ⟩ G is the normal core of ⟨ x ⟩ in G. In this paper, we investigate the structure of finite quasi-core-p p-groups. We prove that if the nilpotency class of a quasi-core-p p-group is p + m , then the exponent of its commutator subgroup cannot exceed p m + 1 , where p is an odd prime and m is non-negative. If p = 3 , we prove that every quasi-core-3 3-group has nilpotency class at most 5 and its commutator subgroup is of exponent at most 9. We also show that the Frattini subgroup of a quasi-core-2 2-group is abelian.

FINITE -GROUPS ALL OF WHOSE NONNORMAL SUBGROUPS HAVE BOUNDED NORMAL CORES

Given a positive integer $m$, a finite $p$-group $G$ is called a $BC(p^{m})$-group if $|H_{G}|\leq p^{m}$ for every nonnormal subgroup $H$ of $G$, where $H_{G}$ is the normal core of $H$ in $G$. We show that $m+2$ is an upper bound for the nilpotent class of a finite $BC(p^{m})$-group and obtain a necessary and sufficient condition for a $p$-group to be of maximal class. We also classify the $BC(p)$-groups.

Toward an inner connection of SNe Ic, SLSNe Ic, XRF connected SNe, SNe Ic-BL, and GRB connected SNe

Type Ic supernovae can be classified as normal supernovae Ic, type Ic super-luminous supernovae, X-ray flash-connected supernovae, broad-line supernovae Ic, and gamma-ray burst-connected supernovae. Here we suggest an inner connection for all kinds of supernovae Ic which is based on whether a pair of jets are successfully launched: a normal supernovae Ic is a normal core collapsar without jets launched; a gamma-ray burst-associated supernovae Ic is a core collapsar with relativistic jets launched and successfully breaking out the envelope of the progenitor; an X-ray flash-associated supernovae Ic is a core collapsar with jets launched but can only develop a relativistic shock breakout; a broad-line supernovae Ic is an off-axis gamma-ray burst or an X-ray flash-associated supernova; and a type Ic super-luminous supernovae is close to the X-ray flash-connected supernovae Ic, but the shock breakout is not relativistic and most of the jet energy is deposited into the supernova component. Based on the luminosity-distance diagram, we derived the luminosity function of all different types of supernovae Ic as a whole. We also show that the normal supernovae Ic and gamma-ray burst-connected supernovae Ic have similar accumulative distributions.

Wet Core Drilling of CFRP with an Electrodeposited Diamond Core Drill - Effects of Cutting Conditions on Chip Evacuation and Core Jamming

This study investigated the cutting characteristics of electrodeposited diamond core drill when used to drill a CFRP under wet condition. The effects of different tool shapes, grain sizes and feed rates were examined. A normal core drill, an eccentric with slits core drill (E.S.), and an eccentric with slits and chamfers core drill (E.S.C.) were used. The normal core drill had the shape of a hollow cylinder. The E.S. core drill had the inner cylinder shifted from the center of this tool and slits in the bottom of this tool. The E.S.C. core drill had chamfers on the periphery of this tool. The normal core drill caused severe workpiece core jamming even at 1st hole drilling, and its electro-deposited area was covered entirely by adhered chips. In the case of the E.S. core drill and E.S.C. core drill, the workpiece core did not jam and the thrust force was smaller than that of the normal core drill. The effect of chamfers was little. The E.S.C. core drill with #200 caused smaller surface roughness than that with #100. However, the thrust force was two times larger, and the delamination was observed at the exit point of the hole. In the lower feed rate per revolution the better surface roughness and the lower thrust force were obtained irrespective of the tool shape while the cutting speed showed little effect.