Hard X-ray emission lines from the decay of 44_Ti in the remnant of Supernova 1987A
Publication date: 18 October 2012
Authors: Grebenev, S., et al.
Copyright: Nature Publishing Group
It is assumed that the radioactive decay of 44Ti powers the infrared, optical and UV emission of a supernova remnant since the complete decay of 56Co and 57Co (3-4 years after the explosion) until the beginning of active interaction of the ejecta with the surrounding matter. Simulations show that 44Ti is synthesized in an amount of M44 ~ (0.02-2.5)×10-4 MSun in core-collapse supernovae. Hard X/gamma-rays from this decay have been unambiguously observed from Cassiopeia A only, leading to the suggestion that the high values of M44 occur in exceptional cases. For the Supernova 1987A remnant, an upper limit M44 <= 10-3 MSun was obtained from direct X-ray observations12, and an estimation M44 ~ (1-2)×10-4 MSun - from infrared light-curves and UV spectra by complex model dependent computations. Here we report observations of hard X-rays from SNR 1987A in the narrow band containing two direct-escape lines of 44Ti at 67.9 and 78.4 keV. The measured line fluxes imply sufficient energy to power the remnant at late times. An initial mass of 44Ti was estimated to be (3.1 +/- 0.8)×10-4 MSun, which is near the upper bound of theoretical predictions.Link to publication