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

Jean Ballet (SAp, CEA Saclay)Rencontres de Blois, Wednesday May 21st, 2008

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.

HESS

Point source

XMM-Newton mosaic

Acero et al 2008

Central Compact Object

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 on global parameters

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 remnantsAnalytic (1D self-

similar) hydrodynamics

Ionized hot gasShock accelerated particles

Accelerated particles throughout Thermal spectrum

Non-thermal spectrum 3D (X,Y,E) model

AccelerationIonization, electron heating

Propagation Cooling

Emission

Emission

Projection

Projection

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 :

Arnett 1988, ApJ 331, 377

Ejecta

Chevalier 1983, ApJ 272, 765; Decourchelle et al 2000, ApJL 543, 57

ejecta

Reverse shock

ISM

Forward shock

Leptonic model

ASCA

ATCA

H.E.S.S.

IC

Synchrotron

Pions

E(eV)

E2d

N/d

E (

eV

.cm

-2.s

-1) Flat ambient density n0

= 8 10-3 cm-3

Distance D = 1 kpc

Electron/proton = 10-2

Mag field B0 = 3 μG

Mshocked = 0.6 Mo

Epmax = 40 TeV

<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 Aharonian et al. 2006, A&A 449, 223

Hadronic model

ASCA

ATCA

H.E.S.S.

IC

SynchrotronPions

E(eV)

E2d

N/d

E (

eV

.cm

-2.s

-1) Flat ambient density

n0 = 0.3 cm-3

Distance D = 1 kpc

electron/proton = 8 10-4

mag field B0 = 12 μG

Mshocked = 7.3 Mo

Epmax = 70 TeV

<Te> = 1.6 keV

Remnant is too small at E = 1051 erg (40’ diameter)

Non thermal spectral fit rather good (fits slope OK)

as in Berezhko & Völk 2006, A&A 451, 981

Predicted thermal emission way too high (as Katz and Waxman 2008, JCAP 1, 18)

Shell model only marginally better

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

H.E.S.S.

GLAST 5 years.

Leptonic

Hadronic

Gamma-rays

• GLAST would see hadronic source in 1 year (but diffusion into neighbouring clouds will not be so favourable)

• H.E.S.S.-2 will see whether spectrum is harder at 100 GeV than at 1 TeV

E(eV)

E2 d

N/d

E (

eV.c

m-2.s

-1)

H.E.S.S.-2

• North hemisphere

• Extended source

for KM3NeT physics case

(preliminary)

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

Jean Ballet (SAp, CEA Saclay)Rencontres de Blois, Wednesday May 21st, 2008

with Gilles Maurin and Gamil Cassam-Chenaï