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Supernova Remnants as Cosmic Rays Accelerators

Supernova Remnants as Cosmic Rays Accelerators. Vladimir S. Ptuskin Institute for Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN), Troitsk, Moscow region 142190, Russia. N cr ~ 10 -10 cm -3 - total number density

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Supernova Remnants as Cosmic Rays Accelerators

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  1. Supernova Remnants as Cosmic Rays Accelerators Vladimir S. Ptuskin Institute for Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN), Troitsk, Moscow region 142190, Russia

  2. Ncr ~ 10-10 cm-3-total number density wcr ~ 1.5 eV/cm3-energy density Emax ~ 3×1020 eV -max. observed energy Lcr~ 5×1040 erg/s - Galactic luminosity in CR δcr ~ 10-3 at 1012 - 1014 eV -anisotropy rg ~ 1E/(Z×3×1015 eV) pc -Larmor radius ulsar

  3. source spectrum E-2.7 cosmic ray density Ncr T Qcr source spectrum E-(2.0 … 2.4) escape time E-(0.3 … 0.6) two power laws: source spectrum + propagation secondary species:Qcr,2 = nvσ21N1 d, 3He, Li, Be, B … p, e+ escape length: X = ρvT ~ 10 g/cm2 at 1 GeV/nucleon

  4. flat-halo diffusion model Ginzburg & Ptuskin 1976 Berezinskii et al 1990 Strong & Moskalenko 1998 surface gas density 2.4 mg/cm2 cosmic-ray halo Sun SNR 2H galactic disk r pure diffusion diffusion + distributed reaccele- ration in ISM Alfven velocity Jones et al 2001

  5. Energy balance local galactic CR energy density 1.5 eV/cm3 needed source power 3×1038 erg/s kpc2 SN kinetic energy 2×1039 erg/s kpc2 (Wsn=1051 erg, 50 Myr-1 kpc-2) ~ 15% efficiency of CR acceleration + pulsars 2×1050 (10 ms/τ)2 erg + stellar winds 2×1038 erg/s kpc2 + Galactic GRBs 1051 erg/105 yr + Galactic Center

  6. SNR blast waves • SN II, SN Ib/c –core collapse of massive stars • SN Ia – thermonuclear explosion of white dwarf in binary system Mechanical energy Wsn ~ 1051 erg (1053 for hypernova) - Free expansion (ejecta-dominated stage): t < 300 yr, ush = 5×108 – 3×109 cm/s, R < 2 pc - Adiabatic deceleration (Sedov stage): t = 103 - 3×104 yr, ush ~ (Wsn/nism)1/5t-3/5 - Radiation cooling: t > 105 yr, R > 20 pc Acceleration by external shock: a) “normal” composition after correction on atomic properties (FIP, volatility) b)delay between nuclear synthesis and acceleration high obs. 59Co/56Fe – δt > 105 yr Soutoul et al. 1978, Leske 1993

  7. Diffusive shock acceleration Fermi 1949, Krymsky 1977, Bell 1978 • average gain • of momentum D(p) SNR ush distribution function (test particles) shock CR intensity time of acceleration resonant diffusion kres~1/rg Larmor radius

  8. Maximum energy condition of acceleration, critical Pecklet number (parameter of modulation) SNR Wsn=1051erg • maximum value -typical in interstellar medium ism n0=1cm-3 diffusion should be anomalously slow near the shock (upstream and downstream) cosmic ray streaming instability in shock precursor Bell 1978, Lagage & Cesarsky 1983, McKenzie & Vőlk 1982, Achterberg 1983, Vőlk et al. 1988, Fedorenko 1990, Bell & Lucek 2001, VSP & Zirakashvili 2003

  9. Bohm limit standard assumption δB ~ Bism Bohm diffusion Nagano & Watson 2000 extra- galactic? galactic knee might be better for SN explosion in progenitor wind Vőlk & Biermann 1988

  10. Nonlinear shock modification by CR pressure upstream downstream u(x) D(p)/u nonmodified shock ush cosmic ray density -∇Pcr precursor subshock ush/r x xsh

  11. not power law spectrum for high Mach number shocks Berezhko & Elliison 1999 Axford 1977, 1981 Eichler 1984 Berezhko et al. 1996 Malkov et al. 2000

  12. overall CR spectrum Berezhko & Völk 2000

  13. Cassiopeia A is bright at all energies of the electromagnetic spectrum. This composite image shows Cassiopeia A at many different wavelengths: radio polarization in red (VLA), X-rays in green (CHANDRA) and optical in blue (HST). Notice the outer shock, visible only in X-rays, as the thin green rim most visible at the top of the image. Also notice the bright ring which is visible at all three wavelengths, and the many different filamentary structures seen at each wavelength. The compact remains of the exploded star are visible only in X-rays, as the bright green spot slightly below and to the left of the geometric center of the bright ring.

  14. observations radio emission νMHz = 4.6 BμGEe,GeV2 E = 50 MeV – 30 GeV (100 GeV for IR) γ = 1.9 – 2.5 We = 1048 – 1049 erg Ginzburg & Syrovatskii 1964 Shklovsky 1976 nonthermal X-rays εkeV = 1 BμG(Ee/120 TeV)2 εmax ~ 100 TeV SN1006 Koyama et al. 1995 Cas AAllen et al. 1997 RX J1713-39Koyama et al. 1997 RX J0852-46 (“Vela jr”)Slane et al 2001 synchrotron γ e SNR γ inverse Compton εγ = ε0(Ee/mec2)2 p e π0 TeV γ – rays electrons/protons εmax ~ 100 TeV SN1006 Tanimori et al 1998 RX J1713Muraishi et al. 2000 Cas AAharonian et al. 2001 γ γ-rays (π0) Ε = 30-3000 MeV γ Cygni, IC443 Esposito et al. 1996 Sturner & Dermer 1996 Only upper limits on TeV γ-rays from many SNRs with ages > 3×103 yrBuckley et al. 1998, Aharonian et al. 2002

  15. SN1006 Tanimori et al. 2001

  16. Problems: - Galactic sources should work up to (1-3)×1018 eV (Fe ?) (reacceleration may help: Axford 1994, Bell 1992, Bykov & Toptygin 2001, Vőlk & Zirakashvili 2004; dispersion of SN parameters: Sveshnikova 2003) • no VHE gamma-rays from not very young SNRs tsnr ≥ 3×103 yr (Buckley et al. 1998, Aharonian et al. 2002) • cosmic ray source spectrum γs = 2.0 - 2.4 (depends on propagation model)

  17. maximum momentum of accelerated particles: abandonment of Bohm limit hypotheses VSP & Zirakashvili 2003 strong streaming instability and non-linear wave interactions in shock precursor: under extreme conditions: Emax ≈ 1017Z(ush/3×104km/s)2 ×(κ/0.1)(ξcr/0.5)Mej1/3n1/6 eV δBmax≈ 10-3 (ush/3×104km/s)n1/2 G Wsn = 1051 erg, Bism = 5 μG, n0 = 0.4 cm-3 ξcr = 0.5, κ = 0.04, a = 0.3

  18. Random field produced by cosmic-ray streaming instability in shock precursor Bell & Lucek 2001 VSP & Zirakashvili 2003 cosmic-ray pressure Alfven velocity wave energy density weak random field: strong random field: characteristic velocity of waves

  19. Average source spectrum spectrum at the shock instantaneous SNR luminosity in run-away cosmic rays SN rate adiabatic stage Q ~ ξcrνsnWsnp-4 (Sedov) - universal spectrum ! average cosmic-ray source spectrum ejecta-dominated stage SNII in RSG wind: Q~ p-6.5at ρstar~ r -10 SNI in uniform medium: Q ~ p-7 (Chevalier – Nadyozhin)

  20. Weaver et al. 1977 Chevalier & Liang 1989 ism R=60pc n=1cm-3 Wsn= 1051 erg, ξcr= 0.5 ρstar~ r-10 ∙ M=10-5 uw=10km/s Rw=2pc RSG wind · Eknee≈ 7×1015 Z eV, ~ ξcrWsnM1/2(Mejuw)-1 Emax ≈ 4×1016 Z eVat tmin = 7 days SNII hot bubble 0.013 cm-3, 3μG Roth et al. 2003 VSP & Zirakashvili 2004 KASCADE

  21. Other proposals on acceleration beyond the knee: R u f ~ 1/p3 ta ~ R/(Fshu) at Di < uR ~ D/(Fshu2) at Di > uR • Reacceleration by multiple shocks SNR SNR OB association u=3×103 km/s B=10-5 G R=30 pc Emax ~ 1017Z eV Axford & Ip 1991, Bykov & Toptygin 1990, 2001 Klepach et al. 2000 SNR • Reacceleration in plerions Ω Crab pulsar few msec pulsar δΦ Ｅθ= Bφur/c pulsar wind u δΦ = 4×1015Z eV – 1019Z eV Bell 1991, 2000, Berezhko 1993 SNR termination shock

  22. Galactic wind acceleration at termination shockJokipii & Morfill 1985, 1991 R = 300 kpc, u = 400 km/s Emax = 3×1018Z eV R u SNR acceleration by traveling shocks and interaction regionsVölk & Zirakashvili 2004 galactic disk

  23. extra- galactic? Nagano & Watson 2000 galactic knee

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