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Rotating massive stars with initial progenitor masses $M_{\rm prog} \sim$ 25 $M_{\odot}$ -- $\sim$140 $M_{\odot}$ can leave rapidly rotating black holes to become collapsars. The black holes and the surrounding accretion disks may develop powerful jets by magneto-hydrodynamics instabilities. The propagation of the jet in the stellar envelope provides the necessary shock heating for triggering nucleosynthesis unseen in canonical core-collapse supernovae. Yet, the energy budget of the jet and its effects on the final chemical abundance pattern are unclear. In this exploratory work, we present a survey on the parameter dependence of collapsar nucleosynthesis on jet energetics. We use the zero-metallicity star with $M_{\rm prog} \sim$ 40 $M_{\odot}$ as the progenitor. The parameters include the jet duration, its energy deposition rate, deposited energy, and the opening angle. We examine the correlations of following observables: (1) the ejecta and remnant masses, (2) the energy deposition efficiency, (3) the $^{56}$Ni production and its correlation with the ejecta velocity, deposited energy, and the ejected mass, (4) the Sc-Ti-V correlation as observed in metal-poor stars, and (5) the [Zn/Fe] ratio as observed in some metal-poor stars. We also provide the chemical abundance table of these explosion models for the use of the galactic chemical evolution and stellar archaeology., Comment: 21 pages, 32 figures. Accepted for publication in Astrophysical Journal, submitted at Jul 13 2022, revised at Jan 17 2023, accepted at Feb 20 2023, published at May 9 2023

Stars of $\sim$ 8 - 10 $M_{\odot}$ on the main-sequence form strongly electron-degenerate O+Ne+Mg core and become super-AGB stars. If such an O+Ne+Mg core grows to 1.38 $M_\odot$, electron captures on $^{20}$Ne$(e,\nu_e)^{20}$F$(e,\nu_e)^{20}$O take place and ignite O-Ne deflagration around the center. In this paper, we perform two-dimensional hydrodynamics simulations of the propagation of the O-Ne flame to see whether such a flame induces a collapse of the O+Ne+Mg core due to subsequent electron capture behind the flame or triggers a thermonuclear explosion. We present a series of models to explore how the outcome depends on model parameters for the central density in the range from $10^{9.80}$ to $10^{10.20}$ g cm$^{-3}$, flame structure of both centered and off-centered ignition kernels, special and general relativistic effects, turbulent flame speed formula and the treatments of laminar burning phase. We find that the O+Ne+Mg core obtained from stellar evolutionary models has a high tendency to collapse into a neutron star. We obtain the bifurcation between the electron-capture collapse and thermonuclear explosion. We discuss the implication in nucleosynthesis and the possible observational signals of this class of supernovae., Comment: 31 pages, 60 figures, submitted to Astrophysical Journal at 30 January 2019, accepted at 26 November 2019, published at 22 January 2020. Text, figures and references updated to match with accepted version. Metadata updated

The properties of the first generation of stars and their supernova (SN) explosions remains unknown due to the lack of their actual observations. Recently many transient surveys are conducted and the feasibility of the detection of supernovae (SNe) of Pop III stars is growing. In this paper we study the multicolor light curves for a number of metal-free core-collapse SN models (25-100 M$_{\odot}$) to provide the indicators for finding and identification of first generation SNe. We use mixing-fallback supernova explosion models which explain the observed abundance patterns of metal poor stars. Numerical calculations of the multicolor light curves are performed using multigroup radiation hydrodynamic code STELLA. The calculated light curves of metal-free SNe are compared with non-zero metallicity models and several observed SNe. We have found that the shock breakout characteristics, the evolution of the photosphere's velocity, the luminosity, the duration and color evolution of the plateau - all the SN phases are helpful to estimate the parameters of SN progenitor: the mass, the radius, the explosion energy and the metallicity. We conclude that the multicolor light curves can be potentially used to identify first generation SNe in the current (Subaru/HSC) and future transient surveys (LSST, JWST). They are also suitable for identification of the low-metallicity SNe in the nearby Universe (PTF, Pan-STARRS, Gaia)., Comment: 15 pages, 19 figures; Accepted for publication in Astrophysical Journal, February 26, 2016

Several highly luminous Type Ia supernovae (SNe Ia) have been discovered. Their high luminosities are difficult to explain with the thermonuclear explosions of the Chandrasekhar-mass white dwarfs (WDs). In the present study, we estimate the progenitor mass of SN 2009dc, one of the extremely luminous SNe Ia, using the hydrodynamical models as follows. Explosion models of super-Chandrasekhar-mass (super-Ch-mass) WDs are constructed, and multi-color light curves (LCs) are calculated. The comparison between our calculations and the observations of SN 2009dc suggests that the exploding WD has a super-Ch mass of 2.2-2.4 solar masses, producing 1.2-1.4 solar masses of Ni-56, if the extinction by its host galaxy is negligible. If the extinction is significant, the exploding WD is as massive as \sim2.8 solar masses, and \sim1.8 solar masses of Ni-56 is necessary to account for the observations. Whether the host-galaxy extinction is significant or not, the progenitor WD must have a thick carbon-oxygen layer in the outermost zone (20-30% of the WD mass), which explains the observed low expansion velocity of the ejecta and the presence of carbon. Our estimate on the mass of the progenitor WD, especially for the extinction-corrected case, is challenging to the current scenarios of SNe Ia. Implications on the progenitor scenarios are also discussed., Comment: 12 pages, 10 figures, 1 table, accepted for publication in ApJ on July 18, 2012

We perform hydrodynamical calculations of core-collapse supernovae (SNe) with low explosion energies. These SNe do not have enough energy to eject the whole progenitor and most of the progenitor falls back to the central remnant. We show that such fallback SNe can have a variety of light curves (LCs) but their photospheric velocities can only have some limited values with lower limits. We also perform calculations of nucleosynthesis and LCs of several fallback SN model, and find that a fallback SN from the progenitor with a main-sequence mass of 13 Msun can account for the properties of the peculiar Type Ia supernova SN 2008ha. The kinetic energy and ejecta mass of the model are 1.2*10^{48} erg and 0.074 Msun, respectively, and the ejected 56Ni mass is 0.003 Msun. Thus, SN 2008ha can be a core-collapse SN with a large amount of fallback. We also suggest that SN 2008ha could have been accompanied with long gamma-ray bursts and long gamma-ray bursts without associated SNe may be accompanied with very faint SNe with significant amount of fallback which are similar to SN 2008ha., Comment: 9 pages, 11 figures, 2 tables, accepted by The Astrophysical Journal, proofed and some references added in v2

Optical spectroscopy and photometry of SN 2006aj have been performed with the Subaru telescope at t > 200 days after GRB060218, the X-ray Flash with which it was associated. Strong nebular emission-lines with an expansion velocity of v ~ 7,300 km/s were detected. The peaked but relatively broad [OI]6300,6363 suggests the existence of ~ 2 Msun of materials in which ~1.3 Msun is oxygen. The core might be produced by a mildly asymmetric explosion. The spectra are unique among SNe Ic in (1) the absence of [CaII]7291,7324 emission, and (2) a strong emission feature at ~ 7400A, which requires ~ 0.05 Msun of newly-synthesized 58Ni. Such a large amount of stable neutron-rich Ni strongly indicates the formation of a neutron star. The progenitor and the explosion energy are constrained to 18 Msun < Mms < 22 Msun and E ~ (1 - 3) 10^{51} erg, respectively., Comment: Accepted for Publication in the Astrophysical Journal Letters (2007, ApJ, 658, L5). 8 pages, including 1 table and 3 figures. Typos corrected

Long-duration gamma-ray bursts (GRBs) are thought to be connected to luminous and energetic supernovae (SNe), called hypernovae (HNe), resulting from the black-hole (BH) forming collapse of massive stars. For recent nearby GRBs~060505 and 060614, however, the expected SNe have not been detected. The upper limits to the SN brightness are about 100 times fainter than GRB-associated HNe (GRB-HNe), corresponding to the upper limits to the ejected $^{56}$Ni masses of $M({\rm ^{56}Ni})\sim 10^{-3}M_\odot$. SNe with a small amount of $^{56}$Ni ejection are observed as faint Type II SNe. HNe and faint SNe are thought to be responsible for the formation of extremely metal-poor (EMP) stars. In this Letter, a relativistic jet-induced BH forming explosion of the 40 $M_\odot$ star is investigated and hydrodynamic and nucleosynthetic models are presented. These models can explain both GRB-HNe and GRBs without bright SNe in a unified manner. Their connection to EMP stars is also discussed. We suggest that GRBs without bright SNe are likely to synthesize $\Mni\sim 10^{-4}$ to $10^{-3}M_\odot$ or $\sim 10^{-6}M_\odot$., Comment: 7 pages, 3 figures. Accepted for publication in the Astrophysical Journal Letters (10 March 2007, v657n2 issue)

Among the important issues in identifying the progenitor system of Type Ia supernovae (SNe Ia), we focus mostly on circumstellar interaction in SN 2002ic, and give brief discussion on the controversial issues of the effects of rotation in merging double degenerates and steady hydrogen shell burning in accreting white dwarfs. SN 2002ic is a unique supernova which shows the typical spectral features of SNe Ia near maximum light, but also apparent hydrogen features that have been absent in SNe Ia. Based on the hydrodynamical models of circumstellar interaction in SN Ia, we suggest that circumstellar medium is aspherical (or highly clumpy) and contains ~1.3 Msun. Possible progenitor systems of SN 2002ic are discussed., Comment: Published in "1604-2004: Supernovae as Cosmological Lighthouses", ASP Conf. Ser. 342, eds. M. Turatto, et al. (ASP), 105-114 (2005)

Late-time BVRIJHK photometry of the peculiar Type Ic SN 2002ap, taken between 2002 June 12 and 2003 August 29 with the MAGNUM telescope, is presented. The light curve decline rate is derived in each band and the color evolution is studied through comparison with nebular spectra and with SN 1998bw. Using the photometry, the OIR bolometric light curve is built, extending from before light maximum to day 580 after explosion. The light curve has a late-time shape strikingly similar to that of the hypernova SN 1998bw. The decline rate changes from 0.018 mag/day between day 130 and 230 to 0.014 mag/day between day 270 and 580. To reproduce the late-time light curve, a dense core must be added to the 1-D hypernova model that best fits the early-time observations, bringing the ejecta mass from 2.5 Msun to 3 Msun without much change in the kinetic energy, which is 4 times 10^51 ergs. This is similar to the case of other hypernovae and suggests asymmetry. A large H-band bump developed in the spectral energy distribution after about day 300, probably caused by strong [Si I] 1.646 micron and 1.608 micron emissions. The near-infrared flux contribution increased simultaneously from <30% to >50% at day 580. The near-infrared light curves were compared with those of other Type Ib/c supernovae, among which SN 1983I seems similar to SN 2002ap both in the near-infrared and in the optical., Comment: 24pages, 9 figures, ApJ in press (10 June 2006, v644 1 issue). Acknowledgements updated

SN 2002ic is a unique supernova which shows the typical spectral features of Type Ia supernovae (SNe Ia) near maximum light, but also apparent hydrogen features that have been absent in SNe Ia. We have calculated hydrodynamical models for the interaction between the SN Ia ejecta and the H-rich circumstellar medium (CSM) to reproduce the observed features of SN 2002ic. Based on our modeling, we suggest that CSM is aspherical (or highly clumpy) and contains about 4-5 solar masses. Possible progenitor systems of SN 2002ic are discussed., Comment: 8 pages, 4 figures. Published in "Frontier in Astroparticle Physics and Cosmology", ed. K. Sato and S. Nagataki (Tokyo: Universal Academy Press) pp. 323-330 (2004 May)

Recently the evidence of the neutrinoless double $\beta$ ($0\nu \beta\beta$) decay has been announced. This means that neutrinos are Majorana particles and their mass hierarchy is forced to inverted mass hierarchy (Type B) or degenerate mass (Type C) patterns in the diagonal basis of charged lepton mass matrix. We estimate the magnitude of $0\nu \beta\beta$ decay in the degenerate neutrinos including the cosmological constraint of neutrino dark matter, since the inverted mass hierarchy pattern always satisfies the cosmological constraint. The absolute value of neutrino mass is constrained by $0\nu \beta\beta$ experiment or cosmology depending on the relative signs (Majorana CP phases) of neutrino masses., Comment: 13 pages, 4 figures, LaTeX

Recently the evidence of the neutrinoless double $\beta$ ($0\nu \beta\beta$) decay has been announced. This means that neutrinos are Majorana particles and their mass hierarchy is forced to certain patterns in the diagonal basis of charged lepton mass matrix. We estimate the magnitude of $0\nu \beta\beta$ decay in the classification of the neutrino mass hierarchy patterns as Type A, $m_{1,2} \ll m_{3}$, Type B, $m_1 \sim m_2 \gg m_3$, and Type C, $m_1 \sim m_2 \sim m_3$, where $m_{i}$ is the $i$-th generation neutrino absolute mass. The data of $0\nu \beta\beta$ decay experiment suggests the neutrino mass hierarchy pattern should be Type B or C. Type B predicts a small magnitude of $0\nu \beta\beta$ decay which is just edge of the allowed region of experimental value in $95% \mathrm{c.l.}$, where Majorana CP phases should be in a certain parameter region. Type C can induce the suitably large amount of $0\nu \beta\beta$ decay which is consistent with the experimental data, where overall scale of degenerate neutrino mass plays a crucial role, and its large value can induce the large $0\nu \beta\beta$ decay in any parameter regions of Majorana CP phases., Comment: 12 pages, 7 figures, LaTeX

It is well known that the Zee model induces small neutrino masses by radiative corrections, where the bi-maximal flavor mixing is possible. We analyze the cosmological condition in order for the baryon asymmetry generated in the early universe not to be washed out in the Zee model. Since the lepton number is violated explicitly in the Zee model, the baryon asymmetry might be washed out through the sphaleron processes together with the lepton-number violating interactions. In this letter, we will show that the baryon asymmetry is {\it not} washed out, although it has been said that the Zee model cannot preserve the baryon asymmetry generated in the early universe. This can be seen by considering an approximately conserved number, $L' \equiv L_e-L_\mu-L_\tau$., Comment: 10 pages, LaTeX

We suggest a simple grand unified theory where the fifth dimensional coordinate is compactified on an $S^1/(Z_2 \times Z_2')$ orbifold. This model contains additional ${\bf 10 + \overline{10}}$, (${\bf 15 + \overline{15}}$) and two ${\bf 24}$ Higgs multiplets in the non-supersymmetric SU(5) grand unified theory. Although this model is non-supersymmetric theory, the gauge coupling unification is realized due to the mass splittings of Higgs multiplets by $S^1/(Z_2 \times Z_2')$ orbifolding. The constraints from the $b \to s \gamma$, $\mu \to e \gamma$, and electron and muon anomalous magnetic moments are also discussed., Comment: 7 pages, LaTeX

We suggest a simple grand unified theory where the fifth dimensional coordinate is compactified on an $S_1/(Z_2 \times Z_2')$ orbifold. This model is based on the supersymmetric flipped $SU(5) \times U(1)$ grand unified theory, which can realize not only the triplet-doublet splitting but also the natural fermion mass hierarchies. The triplet-doublet splitting is realized by $S_1/(Z_2 \times Z_2')$ orbifolding, which also reduces the gauge group as $SU(5) \times U(1) \to SU(3)_c \times SU(2)_L \times U(1)_Z \times U(1)_X$. The suitable fermion mass hierarchies are generated by integrating out extra three sets of vector-like heavy fields which can propagate in five dimensions. The radiative corrections to the large Yukawa coupling of right-handed neutrinos can reduce the gauge group to $SU(3)_c \times SU(2)_L \times U(1)_Y$., Comment: LaTeX,12pages

We comment on ``Linking solar and long baseline terrestrial neutrino experiments''

It has been said that the measurements of $U_{e3}$ in the lepton flavor mixing matrix would help discriminate between the possible solar neutrino solutions under the natural conditions with the neutrino mass hierarchies of $m_1 \ll m_2 \ll m_3$ and $m_1 \sim m_2 \gg m_3$, where $m_i$ is the $i$-th generation neutrino absolute mass. However, it is not true, and the relation between $\sin^2 2 \theta_{12}$ and $U_{e3}$ obtained by Akhmedov, Branco, and Rebelo is trivial in actual. We show in this paper that the value of $U_{e3}$ cannot predict the solar neutrino solutions without one additional nontrivial condition., Comment: 7pages, no figure