Cosmic Ray acceleration at radio supernovae: perspectives for the Cerenkov Telescope Array

Transcription

1 Cosmic Ray acceleration at radio supernovae: perspectives for the Cerenkov Telescope Array A.MARCOWITH ( LABORATOIRE UNIVERS ET PARTICULES DE MONTPELLIER, FRANCE) & M.RENAUD, V.TATISCHEFF, V.DWARKADAS

2 Outlines Context: galactic PeVatrons. The test case of SN 1993J: Modeling particle acceleration Modeling multi-band spectra Perspectives. Conclusions. 2

3 Galactic PeVatrons and cosmic ray spectrum 3 Ptuskin+10 multi-pev domain

4 PeVatrons: observations Produce TeV-PeV gamma-rays Cerenkov Telescope Array (Acero+13) HAWC, Lhasso Produce TeV-PeV neutrinos for km3 instruments (IceCube, Km3net) PeV neutrinos detection (Aartsen+13) 4 Probe the high energy end of galactic cosmic ray spectrum likely around 1 with CTA (Cristofari+13) number of SNR above an integral gamma-ray flux. Blue line: CTA sensitivity limit (3 mcrab) 17/03/2014

5 PeVatrons: Theory PeV CRs and beyond point towards acceleration - in fast (but relativistic, G.Pelletier this workshop) shocks. - Mildly relativistic flows? - pervading massive star winds (Voelk & Bierman 88) Strong magnetic field amplification (MFA) (Bell & Lucek 01, Bell 04, Ptuskin+10) 5 E max = Z(180TeV )u km/s R sh, pc n circ,cc

6 Magnetic Field Amplification: Bell modes 6 Non-resonant (Bell) fast growing modes But grow at small scales: kr L > 1. with ξ = P CR /E kin, φ =ln(e max /E min ) 1 γ max = 224φ 15 ε PeV 3 ξ CR,01 u 0.03c n cm 3 years The maximum energy is limited by the intensity of the escaping CR current (Schure & Bell 13) E CR,max with time for different progenitor winds velocities. From Black Holes to Cosmic Rays - Les Houches- Oct 2013

7 Magnetic field amplification: long wavelength instabilities Large scales can be further amplified by non-linear effects (Reville & Bell 13) or by dynamo action (Bykov+11, Rogachevskii +12). As kr L ~1 improve confinement and higher energies. Here E max is fixed either by the time (Lagage-Cesarsky) or by the geometry (Hillas). eg, Growth rate large scale (Bykov) modes: 7 1 γ max = 1/2 1325ε PeV φ N B,10 ξ CR,0.1 u 0.03c B ISM,µG years N B =δb NR /B ISM = level of fluctuations produced by the NR instability

8 Core collapse Supernovae: the test case SN 1993J Presentation. Particle acceleration modeling (eg Tatischeff 09, Renaud+14 in prep). Multi-wavelength spectra (Renaud+14 in prep). Work paradigm: 8 Cosmic-Rays accelerated right after the outburst in amplified self-generated magnetic field. How SN 93J would have been observed by CTA during weeks after the outburst? To be tested with next explosions of (nearby) ccsne.

9 93J in one slide 9 Occurred in M81 at 3.6 Mpc Type IIb: progenitor red supergiant (RSG, possibly a binary) RSG winds are slow, and high mass loss rate ~ 10-5 sol.mas./yr Well monitored especially by VLBI Multi-frequency light curves using a synchrotron selfabsorption model => magnetic field evolution. Marti-Vidal+11, Bietenholz+10 B~64G (R/1015cm)-1 to be compared with the wind magnetic field - difficult to evaluate => equipartition field: B ~ cm

10 Particle acceleration modeling (Tatischeff 09) Iterative Fit radio data with a synchrotron model + 1D non-linear model (Berezhko & Ellison 99) V sh (t), B u (t), T CSM,ρ u (t) => solutions : f p,f e Solutions stay close to the test-particle regime (Alfvèn heating included). Acceleration efficiency increases with time up to 25% ε NT =F CR /1/2ρ u v sh 3 Downstream: self-similar model by Chevalier 82 two different solutions for B: advection/damping. Maximum energies are associated to the MFA mechanisms. 10

11 Non-resonant streaming instability Growth rate adapted to the 93 J case γ max = 0.16ε 1.18 PeVt days days 3 η 1/600 u 93J n 93J Shorter than the advection time in the precursor (γ max t adv ~3) Vink+04 Saturation (magnetic tension = Lorentz force) (δb ~ (ξ ρ v sh3 ) 1/2 ) δb =16ξ 1/2 0.05φ 1/2 15 t 1 days Gauss Maximum energies (current limited): E max ~ 1 PeV

12 MFA: inclusion of large scale modes Large scale modes: 12 1 γ max = 0.59ε PeV t days 3 u 93J ξ 0.05 φ 1 15 N B,10 B 2 eq,60mg days Equivalent to the advection timescale in the precursor: (γ max t adv ~ 1, for N B =B NRI /B back =10) Filamentation instability not triggered, resonant streaming instability too long, (γ max t adv < 1) Maximum energies fixed either by geometry or age => 10 PeV for protons is reachable. Appear at the very early times: highenergy neutrinos signature is foreseen.

13 More on particle acceleration modeling Procedure: (Renaud+14 in prep) Using non-linear 1D solutions at the shock front: Calculate E max (t) for protons and electrons (radiative losses) Inject a modified non-linear spectrum at the shock. Downstream evolution (One-zone model): Radiative + adiabatic losses Pion production: Secondaries production (electron/positron, neutrinos) Compute time dependent multi-wavelength spectra from primaries and secondaries. GeV-TeV signal accounting from gamma-gamma absorption. 13

14 Gamma-ray radiation modeling Anisotropic Gamma-Gamma absorption over soft photons produced at the SN photosphere (UV,optical) 14 Rear-on R phot R sh Head-on Opacity Opacity produces much less absorption than in isotropic calculations (eg Tatischeff, Kirk+)

15 Detection by HESS and CTA 15 Log 10 E (TeV) Absorbed Gamma-Ray Flux C T A Fer mi Log 10 E 2 dn/de (TeV cm -2 s -1 ) E 2 dn/de (TeV cm -2 s -1 ) t = 1.0 d t = 5.1 d t = 20.2 d t = 49.3 d t = d t = d t = d t = d Log 10 t (days) Energy (TeV) SN 1993J-like case (D=3.6 Mpc) CTA Configurations I-D, Z.A. = 20 o, α = 0.1, 3 h of observing time per night S/N max ~ 35 in 20 h starting at day ~7 in the TeV energy range HESS: S/N max ~ 4.

16 Neutrinos radiation 16 only a few neutrinos above 10 TeV

17 Emission from secondary leptons 17

18 Perspectives Competitive effects: key parameters Mass loss rate/wind velocity 18 main effects CSM density and instability growth rate Target material and gamma-ray luminosity Shock velocity Local ionization degree (Dwarkadas 14) Background magnetic field SN luminosity (peak and light curve) Instability growth rate and acceleration timescale Composition, instability growth Magnetization and obliquity Gamma-gamma absorption 17/03/2014

19 Different SNe classes: SN IIb Perspectives SNe classes interesting but rare events ~5-6% of ccsne (Smartt+09) SN IIL or IIn 19 also ~5-6% of ccsne : more luminous but drop faster and have higher mass loss/wind velocity ratios. Potentially interesting (Renaud+14 in prep). SN IIP aroud 55% of ccsne less luminous in particular at X-rays but also on average lower mass loss/wind velocity ratios (case by case study). SN Ib/Ic mildly relativistic shocks but associated with a WR phase.

20 Conclusions 20 Highest GCR energies are reached for fast shocks. Current driven instabilities grow the fastest in dense environments. Motivate to look for particle acceleration at very young SNR. Test case 93J: Maximum energies: 10 PeV for protons, and up to 25% of the energy flux imparted into CRs. Gamma-ray detection by CTA at 35 sigmas and 4 sigmas for HESS in 20h. High-energy neutrinos expected however the flux is low. Other SN classes may contribute: IIL-IIn seem interesting targets Cosmic-Rays probe the mass: a detailed investigation of the progenitor wind is mandatory to isolate the location of the dominant mass ejected.