Can a Bright and Energetic X-Ray Pulsar Be Hiding Amid the Debris of SN 1987A?

The mass of the stellar precursor of supernova (SN) 1987A and the burst of neutrinos observed at the moment of the explosion are consistent with the core-collapse formation of a neutron star. However, no compelling evidence for the presence of a compact object of any kind in SN 1987A has been found yet in any band of the electromagnetic spectrum, prompting questions on whether the neutron star survived and, if it did, on its properties. Beginning with an analysis of recent Chandra observations, here we appraise the current observational situation. We derived limits on the X-ray luminosity of a compact object with a nonthermal, Crab-pulsar-like spectrum of the order of ≈(1–5) × 1035 erg s−1, corresponding to limits on the rotational energy loss of a possible X-ray pulsar in SN 1987A of ≈(0.5–1.5) × 1038 erg s−1. However, a much brighter X-ray source cannot be excluded if, as is likely, it is enshrouded in a cloud of absorbing matter with a metallicity similar to that expected in the outer layers of a massive star toward the end of its life. We found that other limits obtained from various arguments and observations in other energy ranges either are unbinding or allow a similar maximum luminosity of the order of ≈1035 erg s−1. We conclude that while a pulsar alike the one in the Crab Nebula in both luminosity and spectrum is hardly compatible with the observations, there is ample space for an "ordinary" X-ray-emitting young neutron star, born with normal initial spin period, temperature, and magnetic field, to be hiding inside the evolving remnant of SN 1987A.P.E. and N.R. acknowledge funding in the framework of the NWO Vidi award A.2320.0076. M.M. is supported by an STFC Ernest Rutherford fellowship (ST/L003597/1). R.P. was partly supported by NSF award AST-1616157