Download transparencies - Rencontres de Blois

Rencontres de Blois, Wednesday May 21st, 2008
Jean Ballet (SAp, CEA Saclay)
Modeling photon and neutrino emission from
the supernova remnant RX J1713.7-3946
 Constraints from geometry
 Constraints from spectral energy distribution
 Ingredients for a physical model
 Results and neutrino predictions
with Gilles Maurin (KM3NeT postdoc)
and Gamil Cassam-Chenaï
Rationale
• SNRs are the most likely source of Galactic cosmic-rays on theoretical
grounds (OB associations might be even better, but more diffuse)
• Good observational evidence (radio and X-ray synchrotron from electrons,
TeV emission)
• Must be the place in the Galaxy where the density of TeV to PeV hadrons is
largest
• Good target for neutrino astronomy, if there is enough gas around
Let us look at the best known TeV SNR, RX J1713.7-3946
RX J1713.7-3946
• 1 degree diameter remnant close to Galactic plane (G347.3-0.5).
• Average absorbing column (from X-rays) 5 to 6 1021 cm-2.
• Likely distance is 1 to 1.5 kpc (association with clouds in the West and
absorption value). Radius is then 8 to 13 pc.
• Might be remnant of SN 393 (1600 years old).
• Central compact object is present, therefore SN II. Possibly exploded in
wind-blown shell recently reached by the shock.
• No thermal emission detected. Most likely reason that the ambient density is
low (< 0.02 cm-3). Consistent with the size for reasonable energy (1051 erg).
• X-rays (excluding point sources) are synchrotron, due to electrons accelerated
at TeV energies.
• Emission is filamentary (probably sheets in projection). If width (40” or 0.25
pc) is interpreted as cooling length, implies post-shock B around 80 μG.
XMM-Newton
HESS
mosaic
Point source
Acero et al 2008
Central Compact
Object
Constraints on global parameters
Parameters
 Supernova: age (t0 = 1600 yrs), energy (E = 1051 erg), ejected mass (10 Mo)
 Local conditions: density (n0), distance (1 kpc)
 Particle acceleration: injected fraction (inj =5 10-4), electron/proton (Kep),
magnetic field (B0) following Berezhko and Ellison 1999, ApJ 526, 385
Constraints
 Angular size (E/n0, t0)
 Expansion over time or Doppler width: shock velocity (E/n0, t0)
 Thermal X-ray emission (n0)
 Synchrotron emission level (B0, inj, Kep)
 X-ray synchrotron rim width (B0)
 Width between ejecta and blast wave (inj, B0)
Modeling supernova
remnants
Analytic (1D selfsimilar) hydrodynamics
Acceleration
Ionization, electron heating
Shock accelerated particles
Ionized hot gas
Propagation
Cooling
Emission
Accelerated particles throughout
Thermal spectrum
Projection
Emission
Non-thermal spectrum
Projection
3D (X,Y,E) model
Applied to Tycho SNR (Cassam-Chenaï et al 2007, ApJ 665, 315)
Young SNRs: Hydrodynamics
Power law density profiles => self-similar solutions. Can accommodate stellar winds
and represent approximately shell encounter (ρ as r5 for example)
Initial conditions :
ejecta
Ejecta
Reverse
shock
ISM
Forward
shock
Arnett 1988, ApJ 331, 377
Chevalier 1983, ApJ 272, 765; Decourchelle et al 2000, ApJL 543, 57
as in Aharonian et al. 2006,
A&A 449, 223
 Distance D = 1 kpc
 Electron/proton = 10-2
 Mag field B0 = 3 μG
 Mshocked = 0.6 Mo
E2dN/dE (eV.cm-2.s-1)
 Flat ambient density n0
= 8 10-3 cm-3
Leptonic model
ASCA
H.E.S.S.
Synchrotron
IC
Pions
ATCA
 Epmax = 40 TeV
E(eV)
 <Te> = 0.8 keV (ejecta)
 Parameters OK except magnetic field (X-ray filaments)
 B field could be larger if B turbulence decays behind shock (Pohl et al 2005,
ApJ 626, L101) so that volume for synchrotron is smaller. Allowed by radio.
 Non thermal spectral fit not very good (spectrum too peaked)
as in Berezhko & Völk 2006,
A&A 451, 981
 Distance D = 1 kpc
 electron/proton = 8 10-4
 mag field B0 = 12 μG
 Mshocked = 7.3 Mo
E2dN/dE (eV.cm-2.s-1)
 Flat ambient density
n0 = 0.3 cm-3
Hadronic model
ASCA
H.E.S.S.
Synchrotron
Pions
IC
ATCA
 Epmax = 70 TeV
 <Te> = 1.6 keV
E(eV)
 Predicted thermal emission way too high (as Katz and Waxman 2008, JCAP 1, 18)
 Remnant is too small at E = 1051 erg (40’ diameter)
 Shell model only marginally better
 Non thermal spectral fit rather good (fits slope OK)
 Most of the gas must be outside SNR and cold as in Malkov et al. 2005 (ApJ 624,
L37). Predicts harder spectrum (energy-dependent diffusion ahead of the shock,
not in our code now).
GeV and neutrino emission
E2dN/dE (eV.cm-2.s-1)
Gamma-rays
GLAST 5 years.
H.E.S.S.
Hadronic
(preliminary)
Leptonic
H.E.S.S.-2
E(eV)
• GLAST would see hadronic source in 1
year (but diffusion into neighbouring
clouds will not be so favourable)
• North hemisphere
• Extended source
• H.E.S.S.-2 will see whether spectrum is
harder at 100 GeV than at 1 TeV
for KM3NeT physics case
Rencontres de Blois, Wednesday May 21st, 2008
Jean Ballet (SAp, CEA Saclay)
Modelling photon and neutrino emission from
the supernova remnant RX J1713.7-3946
 Adapted approximate (1D self-similar) but self-consistent SNR
model to predict –ray and neutrino emission
 Computes accurately thermal X-ray emission
 Applied to RX J1713.7-3946: leptonic model can work,
hadronic model requires target gas to be cold (diffusion ahead
of the shock)
 Neutrino emission expected in hadronic model
with Gilles Maurin and Gamil Cassam-Chenaï