Acceleration of GCR in stellar windsand the GCR

22Ne/20Nesource ratio

N. Prantzos (Institut d’Astrophysique de Paris)

Galactic Cosmic Ray Source Composition

CNO overabundant by ~1.5 to 8 ; Most excess CNO attributed to WR stars

No, for elemental ratios Selection effects Refractories: overabundant, but no clear trend with A/Q

Ellison, Meyer, Drury (1997): SN shocks accelerate ISM gas (volatiles) and sputtered grains (refractories)

After taking into account several selection effects, it seems that the Source composition of GCR today is ~solar .

Except for some excess C and Ne22/Ne20 from WR star winds (Cassé and Paul 1982)

Is it solar ? Yes, for most isotopic ratios Volatiles: elements with high A/Q (mass to charge) favored

Solar 0.35.3Ne20Ne22

GCR

Galactic Cosmic Rays : what is the composition of accelerated matter ?

SBM SN

ISM ISM

Wind

C, N, Ne22..

SN

ISM

FS

FS

ISMBA

DC

FSRSSN

Forward Shock accelerates ISM Reverse Shock accelerates SN ejecta

SN Shocks accelerate Superbubble matter Forward Shock accelerates Wind + ISM

A forward shock is launchedat MEXP and runs through

the wind of the star,enriched with products

of H- and/or He- burning, through the unprocessed envelope, and finally in the interstellar medium.

ASSUMPTION: Particle acceleration starts in the beginning

of the Sedov-Taylor (ST) phase, when MSWEPT ~ MEJEC

(BUT: When does it stop ?)

Depending on the previous mass loss of the star, acceleration may occur when the shock is still within the wind (more massive stars) or in the ISM (less massive stars),

thus affecting the composition of accelerated particles.

Ingredients ofstellar models

(convection, mass loss,rotation etc.)determine the

various quantities(MEXP, MREM, MWIND, etc.)

Models with rotation

have larger amountsof processed

material MPROC

MASS (M⊙ )

Stellar models with mass loss and rotation (Hirschi et al. 2005) or no rotation (Chieffi and Limongi 2006)

MASS (M⊙ )

Rotating modelshave larger yields

of He-burning products(C-12, Ne-22, etc.)

in their winds

Integrated mass swept up by the forward shock,as it moves outwards

Stellar models with mass loss and rotation

(Hirschi et al. 2005)

(van Marle et al. 2008) (van Marle et al. 2008)

Fast rotatingZ=0.001 20 M⊙

The circumstellar environment of mass losing stars

For a steady stellar wind, the density profile can be approximated by

Density Radius-2

with 4ùRú(r)r2dr = MWind

Propagation of forward shock into a stellar wind of profile ρ(r) r-2

(Ptuskin and Zirakhasvili 2005, Caprioli 2011)

Caprioli 2011

TIME (yr)

Particle acceleration starts in beginning of ST

and is assumed to stop when the velocity

of the shock drops to MIN

chosen such asthe IMF averaged ratio

Ne22/Ne20 of accelerated particles

equals the observed oneR = (Ne22/Ne20)GCR = 5.3 ⊙

MASS (M⊙ )

The IMF averaged ratioNe22/Ne20

of accelerated particlesequals the observed one

R = (Ne22/Ne20)GCR = 5.3 ⊙for MIN=1900 km/sfor rotating models

and 2400 km/s for non-rotating ones

HMM05

CL06

A1: Beginning ST and accelerationA2: End acceleration S=1900 km/s The forward shock accelerates

particles from a pool of massMACC = A2 – A1

between the beginning of ST (A1)and =1900 km/s (A2)

PNiA i

R01

E Q(E) dE = f E0

Energy of accelerated particles

Mass of accelerated particles

mACC =P

NiA i

Efficiency of acceleration

W = M ACC

mACC = a few 10à 6

Processedmaterial

Are GCR accelerated inSuperbubbles ?

SN eject at explosionmuch larger amounts of Ne20

than in their winds

but they eject amounts of Ne22 comparable to

the ones of their winds

The Ne22/Ne20 ratio produced by a stellar generation

(averaged over the IMF)should be close to solar

(if not: problems with globalNucleosynthesis)

In a superbubble, material from the whole IMF should be mixed and accelerated

In a superbubblethe time integrated (GCR)

Ne22/Ne20 ratioremains compatible with

the observed GCR oneONLY for a short early period

and ONLY if no originalmaterial is left over.

Most of the time, and in realistic conditions

Ne22/Ne20 is close to solar

Superbubbles are NOT at the origin of GCR Ne22/Ne20

nor at the origin of GCR.(Contrary to Higdon et al. 1998,Higdon and Lingenfelter 2003,

Binns et al. 2005, 2008)