Expected Gamma-Ray Emission of SN 1987A in the Large Magellanic Cloud (d = 50 kpc) E.G.Berezhko 1, L.T. Ksenofontov 1, and H.J.Völk 2 1 Yu.G.Shafer Institute of Cosmophysical Research and Aeronomy, Yakutsk, Russia. 2 Max-Planck-Institut für Kernphysik, Heidelberg, Germany. Paper 106, 32 nd ICRC, Beijing 2011

Free BSG wind Hot shocked BSG wind Free RSG wind H II region (swept up RSG wind) Equatorial Ring Cool shell lg N gas lg r RTRT R IIR R T = 3.1x cm R II = 6.1x cm R R = 6.8x cm 0.3 cm cm cm -3 Circumstellar environment of massive progenitor star (Chevalier & Dwarkadas 1995)

Hot shocked BSG wind Free RSG wind ρ  r -2 cool shell SN shock (present position) Radio emission comes predominantly from electron acceleration by quasi- spherical shock in HII region. Shock expands in HII region with constant speed. Equatorial part of SN shock has temporarily decelerated in this region. HII region SNR evolution observed since explosion ! Acceleration model approximates circum- stellar environment by spherical shells (Berezhko & Ksenofontov 2000, 2006) Recent data and long-term evolution considered here

Model calculation of shock acceleration of nuclei (protons) and electrons in this ~ 24 yr old SNR. Time-dependent, spherical symmetry: Gas dynamics for thermal gas Kinetic equations for CR electron and proton distributions N e (p,r, t ) and N p (p,r, t ) Injection strength of suprathermal particles at shock (  degree of nonlinearity) plus e:p - ratio derived from comparison of electron distribution with observed, time- variable overall synchrotron spectrum, e.g. spectral index and amplitude Gas heating in shock precursor due to dissipation of self-excited scattering fluctuations Time-dependent, amplified magnetic field assumed

Overall hydrodynamics, injection rate η, e/p-ratio K ep SN 1987A Type II (Blue Supergiant progenitor) Distance d = 50 kpc Explosion energy E SN = 1.5 × erg Ejecta mass = 10 M Sun (e.g. McCray 1993) Amplified B-field assumed: B 0 2 /(8π) ≈ 3x10 -3 ρV s 2, where B d = σB 0 ; B 0 = amplified precursor field B d = downstream field σ = shock compression ratio (Völk et al. 2005). Presently: B d ~ 10 mG Radio data from Ng et al. 2008

Time variation of injection rate η(t) inferred from decreasing radio spectral index α(t), cf. Zanardo et al. (2010). Plausible from increasingly more quasi-perpendicular shock in dense equatorial ring. Evolution beyond ring passage unknown, possibly remaining low. Both possibilities considered.

Synchrotron Spectral Energy Density vs. frequency. Spectral softening beyond Hz due to synchrotron losses in ≈ 20 mG down- stream field. Consistent with synchrotron nature of hard X-ray emission Soft Hard X-rays Zanardo et al Park et al Synchrotron flux increasing until ~ , then tapering off in Red Supergiant Wind region.

Expected spatially integrated radio flux as function of time, together with ATCA observations (Zanardo et al. 2010) ATCA 1.4 GHz data

Integral gamma-ray Spectral Energy Density vs. energy Theoretical flux renormalized by factor f re = 0.2 due to underlying Archimedean spiral field topology: Still high large-scale turbulence due to strong ionization and radiative cooling Very hard spectrum beyond eV due to strong shock modification. Present energy flux density ≈ 4 x erg cm -2 s -1. Expected to grow by factor of ~2 during next 20 yrs. Subsequent decrease  R s -1 due to rapid decrease of ISM density ρ  R s -2

Conclusions 1) Gamma-ray flux between 0.1 and 10 TeV expected to be quite high at present epoch. Increase by no more than a factor of 2 in future. Quite close to the present H.E.S.S. upper limit  deep observations worthwhile 2) Detection in the TeV range would be an important element for consistent picture for this object 3) In particular evidence for efficient CR production and magnetic field amplification for a core collapse SN at a very early stage of the evolution of its remnant.