Nucleosynthesis of 56Ni in wind-driven Supernova Explosions and Constraints on the Central Engine of Gamma-Ray Bursts

📝 Abstract

Theoretically expected natures of a supernova driven by a wind/jet are discussed. Approximate analytical formulations are derived to clarify basic physical processes involved in the wind/jet-driven explosions, and it is shown that the explosion properties are characterized by the energy injection rate (Edot_iso) and the mass injection rate (Mdot_iso). To explain observations of SN 1998bw associated with Gamma-Ray Burst (GRB) 980425, the following conditions are required: Edot_iso Mdot_iso > ~ 10^{51} erg M_sun s^{-2} and Edot_iso > ~ 2 x 10^{52} erg s^{-1} (if the wind Lorentz factor Gamma_w ~ 1) or Edot_iso > ~ 7 x 10^{52} erg s^{-1} (if Gamma_w » 1). In SN 1998bw, 56Ni (~ 0.4M_sun) is probably produced in the shocked stellar mantle, not in the wind. The expected natures of SNe, e.g., ejected 56Ni masses and ejecta masses, vary depending on Edot_iso and Mdot_iso. The sequence of the SN properties from high Edot_iso and Mdot_iso to low Edot_iso and Mdot_iso is the following: SN 1998bw-like – intermediate case – low mass ejecta (< ~ 1M_sun $) where 56Ni is from the wind – whole collapse. This diversity may explain the diversity of supernovae associated with GRBs. Our result can be used to constrain natures of the wind/jet, which is linked to the central engine of GRBs, by studying properties of the associated supernovae.

💡 Analysis

Theoretically expected natures of a supernova driven by a wind/jet are discussed. Approximate analytical formulations are derived to clarify basic physical processes involved in the wind/jet-driven explosions, and it is shown that the explosion properties are characterized by the energy injection rate (Edot_iso) and the mass injection rate (Mdot_iso). To explain observations of SN 1998bw associated with Gamma-Ray Burst (GRB) 980425, the following conditions are required: Edot_iso Mdot_iso > ~ 10^{51} erg M_sun s^{-2} and Edot_iso > ~ 2 x 10^{52} erg s^{-1} (if the wind Lorentz factor Gamma_w ~ 1) or Edot_iso > ~ 7 x 10^{52} erg s^{-1} (if Gamma_w » 1). In SN 1998bw, 56Ni (~ 0.4M_sun) is probably produced in the shocked stellar mantle, not in the wind. The expected natures of SNe, e.g., ejected 56Ni masses and ejecta masses, vary depending on Edot_iso and Mdot_iso. The sequence of the SN properties from high Edot_iso and Mdot_iso to low Edot_iso and Mdot_iso is the following: SN 1998bw-like – intermediate case – low mass ejecta (< ~ 1M_sun $) where 56Ni is from the wind – whole collapse. This diversity may explain the diversity of supernovae associated with GRBs. Our result can be used to constrain natures of the wind/jet, which is linked to the central engine of GRBs, by studying properties of the associated supernovae.

📄 Content

arXiv:0901.0410v1 [astro-ph.HE] 5 Jan 2009 Mon. Not. R. Astron. Soc. 000, 1–10 (2008) Printed 1 November 2018 (MN LATEX style file v2.2) Nucleosynthesis of 56Ni in wind-driven Supernova Explosions and Constraints on the Central Engine of Gamma-Ray Bursts Keiichi Maeda1⋆and Nozomu Tominaga2 1Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Kashiwano-ha 5-1-5, Kashiwa-shi, Chiba 277-8568, Japan 2Division of Optical and Infrared Astronomy, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan ABSTRACT Theoretically expected natures of a supernova driven by a wind/jet are discussed. Approximate analytical formulations are derived to clarify basic physical processes involved in the wind/jet-driven explosions, and it is shown that the explosion prop- erties are characterized by the energy injection rate ( ˙Eiso) and the mass injection rate ( ˙Miso). To explain observations of SN 1998bw associated with Gamma-Ray Burst (GRB) 980425, the following conditions are required: ˙Eiso ˙Miso ≳1051 erg M⊙s−2 and ˙Eiso ≳2 × 1052 erg s−1 (if the wind Lorentz factor Γw ∼1) or ˙Eiso ≳7 × 1052 erg s−1 (if Γw ≫1). In SN 1998bw, 56Ni (∼0.4M⊙) is probably produced in the shocked stellar mantle, not in the wind. The expected natures of SNe, e.g., ejected 56Ni masses and ejecta masses, vary depending on ˙Eiso and ˙Miso. The sequence of the SN prop- erties from high ˙Eiso and ˙Miso to low ˙Eiso and ˙Miso is the following: SN 1998bw-like – intermediate case – low mass ejecta (≲1M⊙) where 56Ni is from the wind – whole collapse. This diversity may explain the diversity of supernovae associated with GRBs. Our result can be used to constrain natures of the wind/jet, which is linked to the central engine of GRBs, by studying properties of the associated supernovae. Key words: gamma-ray: bursts – supernovae: general – supernovae: individual (SN 1998bw) – nuclear reactions, nucleosynthesis, abundances. 1 INTRODUCTION Gamma-Ray Bursts (GRBs) are energetic cosmological events, emitting ≳1051 ergs in γ-ray. A leading model for the central engine of GRBs is the formation of a black hole (BH) and an accretion disk, following the gravitational col- lapse of a massive star whose main sequence mass (Mms) is at least as large as 25M⊙(for reviews, see Woosley & Bloom 2006; Nomoto et al. 2007). A relativistic flow gen- erated by neutrino annihilation (Woosley 1993; MacFadyen & Woosley 1999) or magnetic activity (Brown et al. 2000; Proga et al. 2003) is proposed to trigger a GRB. A link between (a class of) GRBs and Type Ic super- novae (SNe Ic) has been established observationally. The most convincing cases for the supernovae associated with GRBs (hereafter GRB-SNe) have been provided by spectro- scopic detection of supernova features in an optical afterglow of a GRB or at the position consistent with a GRB. Three ⋆E-mail: keiichi.maeda@ipmu.jp nearby GRB-SNe detected in this way are found to be sim- ilar to one another. The category includes GRB 980425/SN 1998bw (the proto-typical GRB-SN; Galama et al. 1998), GRB 030329/SN 2003dh (Hjorth et al. 2003; Kawabata et al. 2003; Matheson et al. 2003; Stanek et al. 2003), and GRB 031203/SN 2003lw (Malesani et al. 2004; Thomsen et al. 2004). Optical observations of these GRB-SNe are well ex- plained by an explosion of a carbon-oxygen (CO) star, which has evolved from a massive star (Mms ∼40M⊙) and has lost its H- and He-envelopes during the hydrostatic evolu- tionary phase (Iwamoto et al. 1998; Woosley et al. 1999; Nakamura et al. 2001a; Mazzali et al. 2003, 2006). The ki- netic energy (EK) of the expansion is large, E51 ≡EK/1051 ergs ≳10 (note that E51 ∼1 for canonical supernovae). They eject ∼0.3 −0.7M⊙of 56Ni (which powers the SN luminosity by the decay chain 56Ni →Co →Fe). Hereafter, the mass of 56Ni is denoted by M(56Ni). Recently, another example of the association has been reported (Della Valle et al. 2008; Soderberg et al. 2008), i.e., GRB 081007/SN Ic 2 K. Maeda and N. Tominaga 2008hw, while the observed properties of this SN have not been modeled yet. Despite the similarity within the well studied cases men- tioned above, GRB-SNe do seem to have diverse properties. Peak magnitudes of so-called supernova bumps seen in GRB optical afterglows show diversity (Zeh, Klose, & Hartmann 2004; Woosley & Bloom 2006), highlighted by sub-luminous (possible) SNe in GRBs 040924 and 041006 (Soderberg et al. 2006). A few GRBs show no evidence for the supernova bump (Hjorth et al. 2000; Price et al. 2003). Non-detection of SN features in two nearby GRBs 060505 and 060614 has been reported, placing the upper limit to brightness of pos- sible underlying SNe ∼100 times fainter than SN 1998bw (Della Valle et al. 2006; Fynbo et al. 2006; Gal-Yam et al. 2006). In spite of the observational constraints, the explosion mechanism of GRBs and GRB-SNe are still unknown. In particular, how properties of the central engine are related to the bulk expansion of the

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