ISO/SWS observations of SN 1987A*
II. A refined upper limit on the
mass of 
Ti in the ejecta of SN 1987A
1
Stockholm Observatory, 133 36 Saltsjöbaden, Sweden
2
European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
Corresponding author: P. Lundqvist, peter@astro.su.se
Received:
2
March
2001
Accepted:
17
May
2001
ISO/SWS observations of SN 1987A on day 3425 show no emission in
[Fe I] 24.05 
and [Fe II] 25.99 down to the limits ~0.39 Jy and ~0.64 Jy, respectively. Assuming a homogeneous
distribution of 44Ti inside 
and negligible dust cooling,
we have made time dependent theoretical
models to estimate an upper limit on the mass of ejected 44Ti.
Assessing various uncertainties of the model, and checking the late optical
emission it predicts, we obtain an upper limit of 
.
This is lower than in our previous estimate using other ISO data,
and we compare our new
result with other models for the late emission, as well as with expected yields
from explosion models. We also show that steady-state models for the optical
emission are likely to overestimate the mass of ejected 44Ti.
The low limit we find for the mass of ejected 44Ti could be higher if dust
cooling is important. A direct check on this is provided by the
gamma-ray emission at 1.157 Mev as a result of the radioactive decay
of 44Ti.
Key words: supernova: individual: SN 1987A / nucleosynthesis / supernovae: general
© ESO, 2001