INTEGRAL finds titanium in supernova remnant 1987A
This image shows the patch of the sky surrounding the remnant of supernova remnant 1987A (SNR 1987A) as seen in three different bands at hard X-ray energies with ESA's INTEGRAL observatory. The remnant of this supernova, first detected in February 1987, is located in the Large Magellanic Cloud, one of the Milky Way's satellite galaxies, at a distance of about 166,000 light-years.
The central panel is based on data collected in the 65-82 keV band, which encompasses two of the emission lines produced during the radioactive decay of the isotope titanium-44, at 67.9 and 78.4 keV, respectively. The panel on the left is based on data collected in the 48-65 keV band, whereas the panel on the right is based on data collected in the 82-99 keV band. The presence of signal corresponding to the position in the sky of SNR 1987A only in the energy range between 65 and 82 keV demonstrates that the signal does arise from line emission.
This image represents the first detection of titanium-44 in this supernova remnant, allowing astronomers to measure the amount of this key isotope synthesised by the progenitor star of this supernova before the explosion. This is equivalent to 0.03 per cent the mass of the Sun, demonstrating that the radioactive decay of titanium-44 has been powering the source for the past 20 years.
Also seen in the field of view are two other bright sources of high-energy emission, the pulsar PSR B0540-69 and the X-ray binary LMC X-1, which consists of a stellar-mass black hole accreting matter from a companion star. Both of these sources are also in the Large Magellanic Cloud. The emissions from X-ray binaries and pulsars exhibit quite different behaviours across the spectrum, particularly at these energies; this is why PSR B0540-69 shines brightly in all three energy bands, whereas the emission from LMC X-1 becomes fainter at energies larger than 50-100 keV.
The image is based on about 1650 hours of exposure. The field of view of each panel is about 1 degree across.