Nozomu Tominaga

Nucleosynthesis in core-collapse supernovae and GRB-metal-poor star connection

We review the nucleosynthesis yields of core‐collapse supernovae (SNe) for various stellar masses, explosion energies, and metallicities. Comparison with the abundance patterns of metalpoor stars provides excellent opportunities to test the explosion models and their nucleosynthesis. We show that the abundance patterns of extremely metal‐poor (EMP) stars, e.g., the excess of C, Co, Zn relative to Fe, are in better agreement with the yields of hyper‐energetic explosions (Hypernovae, HNe) rather than normal supernovae.We note that the variation of the abundance patterns of EMP stars are related to the diversity of the Supernova‐GRB connection. We summarize the diverse properties of (1) GRB‐SNe, (2) Non‐GRB HNe/SNe, (3) XRF‐SN, and (4) Non‐SN ORB. In particular, the Non‐SN GRBs (dark hypernovae) have been predicted in order to explain the origin of C‐rich EMP stars. We show that these variations and the connection can be modeled in a unified manner with the explosions induced by relativistic jets. Finally, w...

Evaluation of large pixel CMOS image sensors for the Tomo-e Gozen wide field camera

Tomo-e Gozen (Tomo-e) is a wide field optical camera for the Kiso 1.05 m f/3.1 Schmidt telescope operated by the University of Tokyo. Tomo-e is equipped with 84 chips of front-illuminated CMOS image sensors with a microlens array. The field of view is about 20 square degrees and maximum frame rate is 2 fps. The CMOS sensor has 2160x1200 pixels and a size of pixel is 19 microns, which is larger than those of other CMOS sensors. We have evaluated performances of the CMOS sensors installed in Tomo-e. The readout noise is 2.0 e- in 2 fps operations when an internal amplifier gain is set to 16. The dark current is 0.5 e-/sec/pix at room temperature, 290K, which is lower than a typical sky background flux in Tomo-e observations, 50 e-/sec/pix. The efficiency of the camera system peaks at approximately 0.7 in 500 nm.

Core-Collapse Supernovae in the Early Universe: Radiation Hydrodynamics Simulations of Multicolor Light Curves

The properties of the first generation of stars and their supernova (SN) explosions remain unknown due to the lack of their actual observations. Pop III stars may have been very massive and predicted to be exploded as pair-instability SNe, but the observed metal-poor stars show the abundance patterns which are more consistent with yields of core-collapse SNe. We study the multicolor light curves for a metal-free core-collapse SN models (massive stars of 25100 solar mass range) to determine the indicators for the detection 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 the multigroup radiation hydrodynamic code STELLA. The calculated light curves of metal-free SNe are compared with our calculations of non-zero metallicity models and observed SNe.

Electron-capture supernovae of super-asymptotic giant branch stars and the Crab supernova 1054

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...