Title: Probing core collapse: 44Ti and 60Co nucleosynthesis in SN 1987A
Proposal ID: 0120148
Subject category: Nucleosynthesis
Principal investigator: knoedlseder
Institute: Centre d'Etude Spatiale des Rayonnements
Abstract
SN1987 A in the Large Magellanic Cloud is a once-in-a-lifetime opportunity to observe gamma-ray emission
from a Type II supernova with INTEGRAL. The radioactive isotope 44Ti, emitter of gamma-ray photons at 67.9,
78.4, and 1157 keV, is an ideal tracer to probe core collapse physics, since it is created in appreciable
amounts in the innermost layers of the exploding star. Radioactive decay of 60Co, accompanied by gamma-ray
line emission at 1173 and 1332 keV, is sensitive to the neutron excess in the supernova, providing a unique
chance for a direct measurement of this important parameter. Therefore, we propose to search for the
gamma-ray line signatures that arise from the decay of 44Ti and 60Co produced in SN1987 A. The measurement
of the gamma-ray line fluxes will allow the determination of the 44Ti and 60Co yields in SN1987 A,
providing information about the position of the mass-cut, the maximum temperature and density reached during
the passage of the shock wave in the ejecta, and the neutron excess. The 44Ti line profile will provide
excellent information about the velocity structure of the ejecta close to the mass-cut, and probes the
pre-supernova composition inside 2 Msol. We will use both SPI and IBIS to search for the three gamma-ray
lines of 44Ti, although we only expect to detect the 1157 keV line with SPI within the requested 2000
kiloseconds of exposure time. 60Co is certainly an observational challenge, but due to the rapid decay of
this isotope, INTEGRAL probably represents the last chance to measure its gamma-ray lines in SN1987 A. In
addition to the 2000 kiloseconds, we also request the data rights for all additional observations of the LMC
region in order to search for the 44Ti and 60Co decay signatures of SN1987 A.