TY - JOUR
T1 - Annihilation emission from young supernova remnants
AU - Martin, P.
AU - Vink, J.
AU - Jiraskova, S.
AU - Jean, J.
AU - Diehl, R.
PY - 2010
Y1 - 2010
N2 - Context. A promising source of the positrons that contribute through annihilation to the diffuse Galactic 511 keV emission is the
β+-decay of unstable nuclei like 56Ni and 44Ti synthesised by massive stars and supernovae. Although a large fraction of these
positrons annihilate in the ejecta of SNe/SNRs, no point-source of annihilation radiation appears in the INTEGRAL/SPI map of the
511 keV emission.
Aims. We exploit the absence of detectable annihilation emission from young local SNe/SNRs to derive constraints on the transport
of MeV positrons inside SN/SNR ejecta and their escape into the CSM/ISM, both aspects being crucial to the understanding of the
observed Galactic 511 keV emission.
Methods. We simulated 511 keV lightcurves resulting from the annihilation of the decay positrons of 56Ni and 44Ti in SNe/SNRs and
their surroundings using a simple model. We computed specific 511 keV lightcurves for Cas A, Tycho, Kepler, SN1006, G1.9+0.3
and SN1987A, and compared these to the upper-limits derived from INTEGRAL/SPI observations.
Results. The predicted 511 keV signals from positrons annihilating in the ejecta are below the sensitivity of the SPI instrument by
several orders of magnitude, but the predicted 511 keV signals for positrons escaping the ejecta and annihilating in the surrounding
medium allowed to derive upper-limits on the positron escape fraction of ∼13% for Cas A, ∼12% for Tycho, ∼30% for Kepler and
∼33% for SN1006.
Conclusions. The transport of ∼MeV positrons inside SNe/SNRs cannot be constrained from current observations of the 511 keV
emission from these objects, but the limits obtained on their escape fraction are consistent with a nucleosynthesis origin of the
positrons that give rise to the diffuse Galactic 511 keV emission.
AB - Context. A promising source of the positrons that contribute through annihilation to the diffuse Galactic 511 keV emission is the
β+-decay of unstable nuclei like 56Ni and 44Ti synthesised by massive stars and supernovae. Although a large fraction of these
positrons annihilate in the ejecta of SNe/SNRs, no point-source of annihilation radiation appears in the INTEGRAL/SPI map of the
511 keV emission.
Aims. We exploit the absence of detectable annihilation emission from young local SNe/SNRs to derive constraints on the transport
of MeV positrons inside SN/SNR ejecta and their escape into the CSM/ISM, both aspects being crucial to the understanding of the
observed Galactic 511 keV emission.
Methods. We simulated 511 keV lightcurves resulting from the annihilation of the decay positrons of 56Ni and 44Ti in SNe/SNRs and
their surroundings using a simple model. We computed specific 511 keV lightcurves for Cas A, Tycho, Kepler, SN1006, G1.9+0.3
and SN1987A, and compared these to the upper-limits derived from INTEGRAL/SPI observations.
Results. The predicted 511 keV signals from positrons annihilating in the ejecta are below the sensitivity of the SPI instrument by
several orders of magnitude, but the predicted 511 keV signals for positrons escaping the ejecta and annihilating in the surrounding
medium allowed to derive upper-limits on the positron escape fraction of ∼13% for Cas A, ∼12% for Tycho, ∼30% for Kepler and
∼33% for SN1006.
Conclusions. The transport of ∼MeV positrons inside SNe/SNRs cannot be constrained from current observations of the 511 keV
emission from these objects, but the limits obtained on their escape fraction are consistent with a nucleosynthesis origin of the
positrons that give rise to the diffuse Galactic 511 keV emission.
U2 - 10.1051/0004-6361/201014171
DO - 10.1051/0004-6361/201014171
M3 - Article
SN - 0004-6361
VL - 519
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A100
ER -