A&A 483, 529-535 (2008)

DOI: 10.1051/0004-6361:20079337

## Internal dynamics and particle acceleration in Tycho's SNR

**H. J. Völk**

^{1}, E. G. Berezhko^{2}, and L. T. Ksenofontov^{2}^{1}Max-Planck-Institut für Kernphysik, PO Box 103980, 69029 Heidelberg, Germany

e-mail: Heinrich.Voelk@mpi-hd.mpg.de

^{2}Yu. G. Shafer Institute of Cosmophysical Research and Aeronomy, 31 Lenin Ave., 677980 Yakutsk, Russia

e-mail: berezhko@ikfia.ysn.ru

(Received 28 December 2007 / Accepted 3 March 2008)

** Abstract ***Aims. *The consequences of a newly suggested value for the SN explosion
energy
= 1.2 10^{51} erg are explored for the case of
Tycho's supernova remnant (SNR).*Methods. *A nonlinear kinetic theory of cosmic ray (CR) acceleration in supernova remnants (SNRs) is employed to investigate the properties of Tycho's SNR and their correspondence to the existing experimental
data.*Results. *It is demonstrated that the high mean ratio between the radii of the contact
discontinuity and the forward shock is consistent with the very effective
acceleration of nuclear energetic particles at the forward shock. It is also
argued that consistency of the value
= 1.2 10^{51} erg
with the gas dynamics, acceleration theory, and the existing -ray measurements
requires the source distance *d* to be greater than 3.3 kpc. The
corresponding ambient gas number density is lower than 0.4 cm^{-3}. Since
the expected -ray flux strongly depends on the source distance,
, a future experimental determination of the actual
-ray flux from Tycho's SNR will make it possible to determine the values of the
source distance *d* and of the mean ambient gas density. A simple inverse
Compton model without a dominant population of nuclear CRs is not compatible
with the present upper limit for the -ray emission for any reasonable ambient
interstellar *B*-field.*Conclusions. *Given the consistency between acceleration theory and overall, as well as
internal, gas dynamics, a future -ray detection would make the case for *nuclear* particle acceleration in Tycho's SNR incontrovertible in our
view.

**Key words:**ISM: cosmic rays

**--**acceleration of particles

**--**shock waves

**--**stars: supernovae: individual: Tycho's SNR

**--**radiation mechanisms: non-thermal

**--**gamma-rays: theory

**©**

*ESO 2008*