Three Dimensional Simulation of Gamma Ray Emission from Asymmetric Supernovae and Hypernovae

Hard X- and $\gamma$-ray spectra and light curves resulting from radioactive decays are computed for aspherical (jet-like) and energetic supernova models (representing a prototypical hypernova SN 1998bw), using a 3D energy- and time-dependent Monte Carlo scheme. The emission is characterized by (1) early emergence of high energy emission, (2) large line-to-continuum ratio, and (3) large cut-off energy by photoelectric absorptions in hard X-ray energies. These three properties are not sensitively dependent on the observer's direction. On the other hand, fluxes and line profiles depend sensitively on the observer's direction, showing larger luminosity and larger degree of blueshift for an observer closer to the polar ($z$) direction. Strategies to derive the degree of asphericity and the observer's direction from (future) observations are suggested on the basis of these features, and an estimate on detectability of the high energy emission by the {\it INTEGRAL} and future observatories is presented. Also presented is examination on applicability of a gray effective $\gamma$-ray opacity for computing the energy deposition rate in the aspherical SN ejecta. The 3D detailed computations show that the effective $\gamma$-ray opacity $\kappa_{\gamma} \sim 0.025 - 0.027$ cm$^{2}$ g$^{-1}$ reproduces the detailed energy-dependent transport for both spherical and aspherical (jet-like) geometry.Comment: 24 pages, 13 figures. Figure 7 added in the accepted version. ApJ, 644 (01 June 2006 issue), in press. Resolution of figures lower than the published versio

Optical Emission from Aspherical Supernovae and the Hypernova SN 1998bw

A fully 3D Monte Carlo scheme is applied to compute optical bolometric light curves for aspherical (jet-like) supernova explosion models. Density and abundance distributions are taken from hydrodynamic explosion models, with the energy varied as a parameter to explore the dependence. Our models show initially a very large degree ($\sim 4$ depending on model parameters) of boosting luminosity toward the polar ($z$) direction relative to the equatorial ($r$) plane, which decreases as the time of peak is approached. After the peak, the factor of the luminosity boost remains almost constant ($\sim 1.2$) until the supernova enters the nebular phase. This behavior is due mostly to the aspherical $^{56}$Ni distribution in the earlier phase and to the disk-like inner low-velocity structure in the later phase. Also the aspherical models yield an earlier peak date than the spherical models, especially if viewed from near the z-axis. Aspherical models with ejecta mass \sim 10\Msun are examined, and one with the kinetic energy of the expansion $\sim 2 \pm 0.5 \times 10^{52}$ ergs and a mass of $^{56}$Ni \sim 0.4\Msun yields a light curve in agreement with the observed light curve of SN 1998bw (the prototypical hyper-energetic supernova). The aspherical model is also at least qualitatively consistent with evolution of photospheric velocities, showing large velocities near the z-axis, and with a late-phase nebular spectrum. The viewing angle is close to the z-axis, strengthening the case for the association of SN 1998bw with the gamma ray burst GRB980425.Comment: Accepted by the Astrophysical Journal. 28 pages, 14 figure

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 metal-poor 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 GRB. 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, we examine whether the most luminous supernova 2006gy can be consistently explained with the pair-instability supernova model.Comment: 15 pages, 9 figures. To appear in "Supernova 1987A: 20 Years After: Supernovae and Gamma-Ray Bursters", eds. S. Immler, K. Weiler, & R. McCray (American Institute of Physics) (2007

CO J = 2 - 1 Emission from Evolved Stars in the Galactic Bulge

We observe a sample of 8 evolved stars in the Galactic Bulge in the CO J = 2 - 1 line using the Submillimeter Array (SMA) with angular resolution of 1 - 4 arcseconds. These stars have been detected previously at infrared wavelengths, and several of them have OH maser emission. We detect CO J = 2 - 1 emission from three of the sources in the sample: OH 359.943 +0.260, [SLO2003] A12, and [SLO2003] A51. We do not detect the remaining 5 stars in the sample because of heavy contamination from the galactic foreground CO emission. Combining CO data with observations at infrared wavelengths constraining dust mass loss from these stars, we determine the gas-to-dust ratios of the Galactic Bulge stars for which CO emission is detected. For OH 359.943 +0.260, we determine a gas mass-loss rate of 7.9 (+/- 2.2) x 10^-5 M_Sun/year and a gas-to-dust ratio of 310 (+/- 89). For [SLO2003] A12, we find a gas mass-loss rate of 5.4 (+/- 2.8) x 10^-5 M_Sun/year and a gas-to-dust ratio of 220 (+/- 110). For [SLO2003] A51, we find a gas mass-loss rate of 3.4 (+/- 3.0) x 10^-5 M_Sun/year and a gas-to-dust ratio of 160 (+/- 140), reflecting the low quality of our tentative detection of the CO J = 2 - 1 emission from A51. We find the CO J = 2 - 1 detections of OH/IR stars in the Galactic Bulge require lower average CO J = 2 - 1 backgrounds.Comment: 40 pages, 16 figures, appeared in the 1 March 2013 issue of the Astrophysical Journa

Getting just the Supersymmetric Standard Model at Intersecting Branes on the Z6-orientifold

In this paper, globally N=1 supersymmetric configurations of intersecting D6-branes on the Z6-orientifold are discussed, involving also fractional branes. It turns out rather miraculously that one is led almost automatically to just ONE particular class of 5 stack models containing the SM gauge group, which all have the same chiral spectrum. The further discussion shows that these models can be understood as exactly the supersymmetric standard model without any exotic chiral symmetric/antisymmetric matter. The superpartner of the Higgs finds a natural explanation and the hypercharge remains massless. However, the non-chiral spectrum within the model class is very different and does not in all cases allow for a N=2 low energy field theoretical understanding of the necessary breaking U(1)xU(1)->U(1) along the Higgs branch, which is needed in order to get the standard Yukawa couplings. Also the left-right symmetric models belong to exactly one class of chiral spectra, where the two kinds of exotic chiral fields can have the interpretation of forming a composite Higgs. The aesthetical beauty of these models, involving only non-vanishing intersection numbers of an absolute value three, seems to be unescapable.Comment: 45 pages, 2 figures, v3:some signs corrected in erratum, conclusions unchange

Supernovae in Three-Dimension: A Link to Gamma-Ray Bursts

Observational consequences of a jet-driven supernova (SN) explosion model are presented. The results are compared in detail with optical observations of SN 1998bw associated with a Gamma-Ray Burst. It is shown that the jet model is able to reproduce virtually all the optical observations available for this SN, although a spherical model fails to explain some of observed features. Because of the viewing angle effect, the required kinetic energy of the SN ejecta is reduced to ~ 2 x 10^{52} erg as compared to that obtained by the previous spherical model (~ 5 x 10^{52} erg), but this is still much larger than that of a canonical SN (~10^{51} erg).Comment: 6 pages, 3 figures. Invited talk at "Frascati Workshop 2007: Multifrequency Behaviour of High Energy Cosmic Sources", 28 May - 2 June, 2007, Vulcano, Italy. To apper in the Chinese Journal of Astronomy and Astrophysics (ChJAA

The Connection between Gamma-Ray Bursts and Extremely Metal-Poor Stars as Nucleosynthetic Probes of the Early Universe

The connection between the long GRBs and Type Ic Supernovae (SNe) has revealed the interesting diversity: (i) GRB-SNe, (ii) Non-GRB Hypernovae (HNe), (iii) X-Ray Flash (XRF)-SNe, and (iv) Non-SN GRBs (or dark HNe). We show that nucleosynthetic properties found in the above diversity are connected to the variation of the abundance patterns of extremely-metal-poor (EMP) stars, such as the excess of C, Co, Zn relative to Fe. We explain such a connection in a unified manner as nucleosynthesis of hyper-aspherical (jet-induced) explosions Pop III core-collapse SNe. We show that (1) the explosions with large energy deposition rate, $\dot{E}_{\rm dep}$, are observed as GRB-HNe and their yields can explain the abundances of normal EMP stars, and (2) the explosions with small $\dot{E}_{\rm dep}$ 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 HNe) belong to a continuous series of BH-forming stellar deaths with the relativistic jets of different $\dot{E}_{\rm dep}$.Comment: 8 pages, 6 figures. To appear in "Massive Stars as Cosmic Engines", Proceedings of IAU Symposium 250 (December 2007, Kauai), eds. F. Bresolin, P.A. Crowther, & J. Puls (Cambridge Univ. Press