44Ti ejecta in young supernova remnants

Context.Tracing unstable isotopes produced in supernova nucleosynthesis provides a direct diagnostic of supernova explosion physics. Theoretical models predict an extensive variety of scenarios, which can be constrained through observations of the abundant isotopes(56)Ni and(44)Ti. Direct evidence of the latter was previously found only in two core-collapse supernova events, and appears to be absent in thermonuclear supernovae. Aims.We aim to to constrain the supernova progenitor types of Cassiopeia A, SN 1987A, Vela Jr., G1.9+0.3, SN1572, and SN1604 through their(44)Ti ejecta masses and explosion kinematics. Methods.We analyzed INTEGRAL/SPI observations of the candidate sources utilizing an empirically motivated high-precision background model. We analyzed the three dominant spectroscopically resolved de-excitation lines at 68, 78, and 1157 keV emitted in the decay chain of(44)Ti -> Sc-44 -> Ca-44. The fluxes allow the determination of the production yields of(44)Ti. Remnant kinematics were obtained from the Doppler characteristics of the lines. Results.We find a significant signal for Cassiopeia A in all three lines with a combined significance of 5.4 sigma. The fluxes are (3.3 +/- 0.9) x 10(-5)& x2006;ph & x2006;cm(-2)& x2006;s(-1), and (4.2 +/- 1.0) x 10(-5)& x2006;ph & x2006;cm(-2)& x2006;s(-1)for the(44)Ti and(44)Sc decay, respectively. This corresponds to a mass of (2.4 +/- 0.7) x 10(-4)& x2006;M(circle dot)and (3.1 +/- 0.8) x 10(-4)& x2006;M-circle dot, respectively. We obtain higher fluxes for(44)Ti with our analysis of Cassiopeia A than were obtained in previous analyses. We discuss potential differences. We interpret the line width from Doppler broadening as expansion velocity of (6400 +/- 1900)& x2006;km & x2006;s(-1). We do not find any significant signal for any other candidate sources. Conclusions.We obtain a high(44)Ti ejecta mass for Cassiopeia A that is in disagreement with ejecta yields from symmetric 2D models. Upper limits for the other core-collapse supernovae are in agreement with model predictions and previous studies. The upper limits we find for the three thermonuclear supernovae (G1.9+0.3, SN1572 and SN1604) consistently exclude the double detonation and pure helium deflagration models as progenitors.