On the variability of the X-ray emission from supernova 1987A

Abstract

The hard-X-ray emission observed above 10 keV from SN1987A by the X-ray astronomy satellite Ginga¹ and by the KVANT module² on the MIR station is reasonably well explained^3,4 by Compton down-scattered photons from the decay of ⁵⁶Co. The rising X-ray spectrum detected by Ginga¹ below 10 keV is not understood so easily: some have suggested⁵ that it is due to the interaction of the expanding ejecta with circumstellar matter, others⁶ explain it as synchrotron radiation from the region immediately around a newly formed pulsar. Neither of these models satisfactorily accounts for both the variability observed in the X-ray emission^7,8 (in particular a drop of 30% in 1.5 days in January 1988) and the presence of an emission line at ∼6.8 keV. We suggest here that the X-ray emission is due to the young neutron star being cocooned in matter from a binary companion. The remnant must therefore contain large holes which can explain the early detection of gamma rays and hard X rays without requiring that the Ni (which decayed into Co) was mixed throughout the ejecta.