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

Abstract

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.