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Low-mass population III (PopIII) stars could survive up until the present. They would be found in the halo of Our Galaxy, if they exist. Non-detection of low-mass PopIII stars in our Galaxy suggests that PopIII stars have a top-heavy IMF. On the other hand, some claims that the lack of such stars is as a result of metal enrichment of their surface by accretion of heavy elements from interstellar medium (ISM). We investigate effects of the stellar wind on the metal accretion onto low-mass PopIII stars because accretion of the local ISM onto the Sun is prevented by the solar wind even for neutrals. We find that low-mass PopIII stars traveling across the Galaxy forms the stellar magnetosphere in most of their life. Once the magnetosphere is formed, most of neutral interstellar particles are photoionized before reaching to the stellar surface and are blown away by the wind. This demonstrates that low-mass PopIII stars remain pristine and will be found as metal free stars and that further searches for them are valuable to constrain the IMF of PopIII stars.

An electron-capture supernova (ECSN) is a core-collapse supernova explosion of a super-asymptotic giant branch (SAGB) star with a main-sequence mass MMs ∼ 7 - 9.5M⊙. The explosion takes place in accordance with core bounce and subsequent neutrino heating and is a unique example successfully produced by first-principle simulations. This allows us to derive a first self-consistent multicolor light curves of a core-collapse supernova. Adopting the explosion properties derived by the first-principle simulation, i.e., the low explosion energy of 1.5 × 1050 erg and the small 56Ni mass of 2.5 × 10−3 M⊙, we perform a multigroup radiation hydrodynamics calculation of ECSNe and present multicolor light curves of ECSNe of SAGB stars with various envelope mass and hydrogen abundance. We demonstrate that a shock breakout has peak luminosity of L ∼ 2 × 1044 erg s−1 and can evaporate circumstellar dust up to R ∼ 1017 cm for a case of carbon dust, that plateau luminosity and plateau duration of ECSNe are L ∼ 1042 erg s−1...

The first metal enrichment in the universe was made by a supernova (SN) explosion of a population (Pop) III star (Pop III SN). Chemical abundance in the early universe is recorded in abundance patterns of extremely metal-poor (EMP) stars. Increasing number of the EMP stars are now being discovered and allow us to statistically constrain explosion properties of Pop III SNe. We present Pop III SN models that reproduce well individual abundance patterns of 48 most metal-poor stars with [Fe/H] ≲ −3.5, and derive relations between abundance ratios and explosion properties of Pop III SNe: [(C+N)/Fe] vs. an ejected Fe mass, and [(C+N)/Mg] vs. a remnant mass. Using the relations, distribution of the abundance ratios of EMP stars is converted to that of the explosion properties of Pop III SNe, which can be compared with that of the explosion properties of SNe in the present day. Large samples of EMP stars obtained by ongoing and future EMP star surveys and subsequent high-dispersion spectroscopic observations will further clarify the nature of Pop III SNe in the early universe.

We investigate the formation of the first stars in 60 minihalos found in cosmological simulations, utilizing radiation hydrodynamics simulations. We find ∼70% of the halos host multiple stellar system, while the rest of them have single stars. The stellar mass found in our simulations is in the range of 0.5M⊙ < M < 300M⊙, peaking at several tens of Msun. We do not find that the mass spectrum do not have significant dependence on the formation redshifts and the spin parameters of parent minihalos.

First stars are suggested to be dominated by massive stars. Some massive stars are now known to die as superluminous supernovae (SLSNe). Especially, Type IIn SLSNe show narrow emission lines which are believed to come from dense circumstellar medium (CSM) and the interaction between SN ejecta and dense CSM is presumed to be the reason for the high luminosity. Thanks to the deceleration of SN ejecta by dense CSM, the kinetic energy of SN ejecta is efficiently converted to thermal energy which is eventually emitted as radiation. We show the results of our LC modeling of Type IIn SLSNe performed by using a one-dimensional multigroup radiation hydrodynamics code STELLA. We show that the LCs of Type IIn SLSNe can be actually explained by the interaction between SN ejecta and dense CSM. In addition, we show that the spectra of Type IIn SLSNe tend to be bluer than other kinds of SNe because of the interaction and future NIR satellites like JWST or WISH can potentially detect Type IIn SLSNe appeared at z=10 or higher.

Type II-plateau supernovae (SNe II-P) have so far been observed only at z 1 with shock breakout, that is the brightest radiative phenomenon in a supernova (SN). The first observation of shock breakout from the rising phase is reported in 2008. We construct a theoretical model reproducing the UV-optical light curves (LCs) of the first example and demonstrate that the peak apparent g-band magnitude of the shock breakout would be mg ∼ 26.5 mag if an identical SN occurs at a redshift z = 1, which can be reached by 8m-class telescopes. Furthermore, we present LCs of shock breakout of SN explosions with various main-sequence masses and derive the observable SN rate and reachable redshift as functions of limiting magnitude. The g-band observable SN rate with limiting magnitude 27.5 mag is 3.3 SNe deg−2 day−1 and half of them are located at z > 1.2. It is clear that the shock breakout is a beneficial clue to probe high-z core-collapse SNe.

The first chemical enrichment has been made by supernovae (SNe) of metal-free Population (Pop) III stars. The first generation stars formed from the primeval density fluctuation are called Pop III.1 stars and predicted to be as massive as > 300M⊙. Although such very massive stars (VMSs) had been considered to directly collapse to black holes, the VMSs are recently suggested to be able to explode as gamma-ray bursts (GRBs). In order to clarify whether the VMSs can contribute to the chemical enrichment in the early universe, we present explosive nucleosynthesis in VMS explosions and compare the abundance patterns of their yields with those of the extremely metal-poor (EMP) stars. It is shown that the yields of VMS explosions with explosion energy of 6.3 × 1054 erg cannot reproduce [C/Fe], [Mg/Fe], and [Zn/Fe] simultaneously. This implies that the VMSs are likely not to dominantly contribute to the chemical enrichment in the early universe.

Although the explosion mechanisms of Gamma-ray bursts (GRBs) and Supernovae (SNe) have been investigated theoretically for a long while, they have not been clarified yet and thus it is required to obtain information from the other point of view. In this presentation, I focus on constraints of the extremely metal-poor (EMP) stars. Since the first metal enrichment in the universe was made by GRBs and/or SNe, the EMP stars, formed in the early universe, preserve the nucleosynthetic features of GRBs and/or SNe in their abundance patterns and thus the abundance patterns of the EMP stars can reveal the explosion properties of GRBs and/or SNe. I present nucleosynthesis in explosions with relativistic jets or non-relativistic mildly aspherical energy deposition, assuming GRBs or SNe, and compare the abundance ratios of their yields with those of the EMP stars. The explosion with non-relativistic mildly aspherical energy deposition can explain [Mg/Fe], [Ca/Fe], and [Zn/Fe] but not [Ti/Fe], while the explosion with relativistic jets can explain [Ca/Fe], [Ti/Fe], and [Zn/Fe] but not [Mg/Fe]. This illustrates that the explosion with relativistic jets or non-relativistic mildly aspherical energy deposition cannot fully reproduce the EMP stars solely and implies that the explosion with relativistic jets and non-relativistic mildly aspherical energy deposition, like GRB-SNe, could explain the abundance ratios of EMP stars simultaneously.

We describe the evolution of dust within Population III supernova remnants (SNRs) and investigate the chemical compositions of the dust piled up in their dense shells. We show that the resulting abundance patterns of the major elements in the dense shells are in good agreement with that observed for a Galactic halo star, SDSS J102915+172927. This allows us to propose that SDSS J102915+172927 might be the second-generation star formed in the dust-enriched dense shell of a Population III SNR. We conclude that the segregation of dust from the metal-rich ejecta gas can be an important process in determining the abundance patterns of primitive low-mass stars.

Recent results from the Pierre Auger Observatory (PAO) suggest that ultra‐high energy cosmic rays (UHECRs) involve heavy or intermediate mass nuclei. This indicates that a considerable fraction of heavy nuclei must exist in the accelerating sites. Here, we focus on relativistic jets in gamma‐ray bursts associated with core‐collapse supernovae, which could contain large amount of metal. We investegate the dependence of nuclear composition on the outflow parameters. We show that when ratio of thermal to total energy density at initial radius of the outflow is high, heavy nuclei are dissociated to light particles such as α‐particles during the expansion, even if the outflow initially consists of heavy and intermediate nuclei. This result demonstrates that nuclear composition of the outflow in standard fireball model is dominated by light particles after the acceleration. However, we suggest that if the jets are accelerated by magnetic field, fraction of thermal energy in the jets is not necessarily high and metal nuclei could survive in the jets.

Jet‐induced supernovae (SNe) have been suggested to take place in gamma‐ray bursts (GRBs) and highly‐energetic SNe (hypernovae). I summarize hydrodynamical and nucleosynthetic properties of the jet‐induced explosion of a population (Pop) III 40 M⊙ star. In particular, I present the aspherical effect on nucleosynthetic yield and its dependence on properties of the relativistic jets. Nucleosynthesis in Pop III SNe can be constrained by abundance patterns of extremely metal‐poor (EMP) stars which were formed in the early universe. The jet‐induced SNe acquire favorable features for EMP stars as follows: (1) the ejection of Fe‐peak products and the fallback of unprocessed materials are compatibly realized and (2) the varieties of energy deposition rates in the jet‐induced SNe explains a trend of [C/Fe] in the EMP stars. Furthermore, the variation of energy deposition rates lead the variation of ejected 56Ni(Fe) masses, and thus can explain both GRB‐associated SNe and GRBs without bright SNe, GRBs 060505 and 06...

A long GRB is thought to occur when a massive star ends its life and thus it is expected to be accompanied by a type Ic supernova (SN) which also results from a massive star. Several nearby long GRBs are observed with type Ic SNe. However, some nearby long GRBs are observed without SNe, even though they are close enough to be able to observe the accompanied SNe (e.g., GRB060614). Within our current picture of long GRBs, long GRBs should be accompanied by SNe and these long GRBs without SNe are one of the challenges for the current theory of long GRBs. One possible reason is that the accompanied SNe were so faint that we just missed them. For example, SN 2008ha was only as bright as ∼‐14 mag in the R band at maximum brightness. The explosion energy, ejecta mass, and 56Ni mass of SN 2008ha are estimated as about 1048 erg, 0.1 M⊙, and 0.003 M⊙, respectively. If such a SN is accompanied by long GRBs, we might miss it. We performed numerical calculations of hydrodynamics and radiation transport and confirmed t...

The diversity in brightness and explosion energy of supernovae (SNe) that have recently been observed is remarkable. Determining the origin of unusual SNe, such as extremely faint or extremely luminous ones, or the very energetic explosions associated with GRBs (hypernovae), is very challenging. We present a core‐collapse hypernova model for the extremely luminous Type Ic SN 2007bi as an alternative to the pair‐instability model. We discuss how nucleosynthesis from a variety of SNe is connected to the abundance patterns of extremely metal‐poor stars. Such connections may impose important constraints on the properties of the first stars, such as their evolution with mass accretion, or the asphericity of their explosions.

The first metals in the universe were created in the supernova (SN) explosions of Population III (Pop III) stars, and their remnants are recorded in the abundance patterns of extremely metal‐poor (EMP) stars. The properties of Pop III SNe can thus be constrained by comparing models of their nucleosynthetic yields with abundances in EMP stars. We find that variations in yields in our Pop III SN models account well for the elemental patterns discovered in the 17 most metal‐poor stars with [Fe/H]

A supernova (SN) becomes as bright as a galaxy and is a powerful tool for probing the high‐redshift universe. In particular, it has been suggested that extremely luminous SNe (MR 2, which is difficult for type Ia SNe. Some luminous SNe, such as type IIn SNe, are believed to be powered by the interaction of the SN ejecta with the circumstellar medium. One of the interesting features of interaction‐powered SNe is the fact that they are bright in UV. With their intrinsic brightness in UV, interaction‐powered SNe could unveil the properties of stars at high redshift and probe the primordial universe. We performed multigroup light curve calculations of interaction‐powered SNe using the STELLA code. Based on the synthetic multicolor light curves, we estimate the detectability of interaction‐powered SNe at high redshifts with several telescopes.

We review the properties of supernovae (SNe) as a function of the progenitor’s mass M. (1) 8–10 M⊙ stars are super‐AGB stars and resultant electron capture SNe may be Faint supernovae like Type IIn SN 2008S. (2) 10–13 M⊙ stars undergo Fe‐core collapse to form neutron stars (NSs) and Faint supernovae. (3) 13 M⊙–MBN stars undergo Fe‐core collapse to form NSs and normal core‐collapse supernovae. (4) MBN–90 M⊙ stars undergo Fe‐core collapse to form Black Holes. Resultant supernovae are bifurcate into Hypernovae and Faint supernovae. (5) 90–140 M⊙ stars produce Luminous SNe, like SNe 2007 bi and 2006 gy (6) 140–300 M⊙ stars become pair‐instability supernovae which could be Luminous supernovae (SNe 2007 bi and 2006 gy). (7) Very massive stars with M≳300 M⊙ undergo core‐collapse to form intermediate mass black holes. Some SNe could be more Luminous supernovae (like SN 2006 gy).

Recent observations have revealed remarkably large diversities of supernova properties. We present our challenge to explore the origin of unusual supernovae such as extremely faint and extremely luminous supernovae, and the extremely energetic explosions (hypernovae) associated with the Gamma‐Ray Bursts. In particular, we present a core‐collapse hypernova model for extremely luminous type Ic SN 2007bi as an alternative to the pair‐instability model. We discuss how nucle‐osynthetic properties resulted from unusual supernovae are connected with the unusual abundance patterns of extremely metal‐poor stars. Such connections may provide important constraints on the properties of first stars.

Optical emission from supernovae (SNe) reflects physical properties of SNe, such as mass and kinetic energy of the ejecta and the ejected 56Ni mass, which are closely related to the central remnants, explosion scenarios and progenitor stars of SNe. Modelling of the optical emission has been done mostly under the assumption of spherical symmetry. In this paper, we present multidimensional modelling of optical emission using a multi‐dimensional Monte‐Carlo radiative transfer code, SAMURAI (SupernovA MUlti‐dimensional RAdIative transfer code). We show that all the optical observations of SN 1998 bw/GRB 980425, including the light curve and optical spectra at early and late phases, are consistent with polar‐viewed radiation of the aspherical explosion model. The kinetic energy, which has been estimated to be 30–50×1051 ergs by spherical models, can be reduced to 20×1051 ergs. Such reduction of the kinetic energy is less effective for off‐axis or less aspherical cases. As an observational test of SN asphericit...

Origin of Matter and Evolution of Galaxies: The 10th International Symposium on Origin of Matter and Evolution of Galaxies: From the Dawn of Universe to the Formation of Solar System. 4–7 December 2007. Sapporo, Japan., The calculations for the evolution of dust within Population III supernova remnants (SNRs) are presented, based on the models of dust formed in the unmixed ejecta of Type II SNe. We show that once dust grains collide with the reverse shock penetrating into the ejecta, their fates strongly depend on the initial radius a_ini. For SNRs expanding into the interstellar medium (ISM) with n_[H,0] = 1 cm^[−3], grains of a_ini0.2 µm are injected into the ISM without being eroded significantly. The total mass of surviving dust is 0.01 to 0.8 M☉ for n_[H,0] = 10 to 0.1 cm^[−3]. We also investigate the influence of the piled-up dust on the elemental abundances of the second-generation stars formed in the dense shell of Population III SNRs. The comparison of the calculated elemental abundances with those observed in hyper-metal-poor (HMP) and ultra-metal-poor (UMP) stars indicates that the transport of dust separated from metal-rich gas can be an important process in determining the abundance patterns of Mg and Si in HMP and UMP stars.

First Stars III: First Stars II Conference. Santa Fe, New Mexico, U.S.A. 15–20 July 2007., We present the results of calculations for the evolution of dust within Population III supernova remnants (SNRs), focusing on the dust formed in the unmixed ejecta of Type II SNe. We show that once dust grains inside the He core encounter the reverse shock, they are subject to different fates depending on their initial sizes a_ini. For SNRs expanding into the interstellar medium (ISM) with n_[H,0] = 1 cm^[-3], grains of a_ini < 0.05 μm are trapped in the hot gas and are completely destroyed; grains of a_ini = 0.05-0.2μm are trapped in the dense shell behind the forward shock with the final sizes of 0.001-0.1μm; grains of a_ini > 0.2μm are injected into the ISM without significant destruction. The total mass of surviving dust is 0.01 to 0.8 M☉ and is higher for the lower ISM gas density. We also investigate the elemental abundances of the second-generation stars that form in the dense shell of Population III SNRs, based on the elemental composition of dust piled up in the shell. The comparison of those results with the observations of hyper-metal poor (HMP) stars indicates that the transport of dust segregated from metal-rich gas within a SNR can be responsible for the abundance patterns of Mg and Si in HMP stars.

We present the nucleosynthetic yields of Population III core‐collapse supernovae (SNe) focusing on the cases of hyper‐energetic (Hypernovae, HNe) and hyper‐aspherical (jet‐induced) explosions. We show that (1) the explosions with large energy deposition rate, Ėdep, are observed as GRB‐HNe and their yields can explain the abundances of normal extremely metal‐poor (EMP) stars, and (2) the explosions with small Ėdep are observed as GRBs without bright SNe and can be responsible for the formation of the C‐rich EMP (CEMP) and the hyper metal‐poor (HMP) stars. We thus propose that GRB‐HNe and the Non‐SN GRBs (dark hypernovae) belong to a continuous series of BH‐forming massive stellar deaths with the relativistic jets of different Ėdep. We also show that the very peculiar Si‐poor abundance can also be explained by the angle‐delimited yield of aspherical explosion.

We review the following types of the GRB‐Supernova (SN) connection, which has revealed interesting diversity. (1) GRB‐SNe: The three SNe all explode with energies much larger than those of typical SNe, thus being called Hypernovae (HNe). They are massive enough for forming black holes. (2) Non‐GRB HNe/SNe: Some HNe are not associated with GRBs. (3) XRF‐SN: SN 2006aj associated with X‐Ray Flash 060218 is dimmer than GRB‐SNe and has very weak oxygen lines. Its progenitor mass is estimated to be small enough to form a neutron star rather than a black hole. (4) Non‐SN GRB: Two nearby long GRBs were not associated SNe. Such “dark HNe” have been predicted in order to explain the origin of C‐rich (hyper) metal‐poor stars. This would be an important confirmation of the Hypernova‐First Star connection. We will show our attempt to explain the diversity in a unified manner with the jet‐induced explosion model.

The recent discovery of a hyper metal‐poor (HMP: −5 ≲ [Fe/H] ≲ −4) star have raised a challenging question if these HMP stars are first generation stars in the Universe. We argue that these HMP stars are the second generation stars being formed from gases which were chemically enriched by the first generation supernovae. The key to this solution is the very unusual abundance patterns of these HMP stars with important similarities and differences. We can reproduce these abundance features with the core‐collapse “faint” supernova models which undergo extensive matter mixing and fallback during the explosion (mixing‐fallback model). We also show that the abundance patterns of extremely metal‐poor (EMP: −4 ≲ [Fe/H] ≲ −3) stars are well‐reproduced by a 25 M⊙ hypernova mixing‐fallback model and those of very metal‐poor (VMP: −3 ≲ [Fe/H] ≲ −2) stars are well‐reproduced by a model integrated by Salpeter’s initial mass function over 13 – 50 M⊙ models.

The influence of a large variation of Ye on explosive yield is investigated. We calculate nucleosynthesis with the initial electron fraction Ye ranging from 0.48 to 0.58 in explosive Si burning region in Population III, 25 M⊙ supernovae. We obtain the significant overproduction of odd elements, K and Sc. In the Ye < 0.5 cases light p‐process nuclei are enhanced. We find that the abundance pattern taken from arbitrary mixture of each nucleosynthesis yield in various values of Ye can reasonably explain that in observed extremely metal‐poor stars.

Recently, very accurate observations of abundances of extremely metal‐poor (EMP) stars have been performed with VLT and SUBARU. They determined the abundance patterns of many EMP stars with −4.2 < [Fe/H] < −2. In the result, it is confirmed with small dispersions that the abundance ratios of these stars are obtained as a function of the metallicity. For example, the EMP stars with smaller [Fe/H] have larger [Zn,Co/Fe] and smaller [Cr/Fe]. Therefore Cayrel et al. (2004) and Francois et al. (2004) suggested homogeneous mixing in the Galaxy even below [Fe/H]≲ −3, although this conflicts with the Galactic chemical evolution models. We calculate explosions and nucleosynthesis of population III supernovae (SNe) with mixing‐fallback model (Umeda & Nomoto 2003; 2005; Tominaga et al. 2006) and show that the trends of the abundance ratios with the small dispersions can be understood by the variations of explosion energies and progenitors’ masses in inhomogeneous mixing.