A sensitive search for radio pulses from primordial black holes and distant Supernovae

Abstract

THERE are two mechanisms of current theoretical interest which might generate short ( <1 ms) radio pulses detectable at interstellar or even cosmological distances. In both cases the pulse is generated by the alteration of a magnetic field by an expanding conducting shell. The phenomenon might occur either as the expanding core of a supernova ‘combs’ the star's intrinsic dipole field^1,2, or as the shell of charged particles emitted in the explosion of a primordial black hole (PBH) excludes the surrounding magnetic field³. In the latter case, the resulting radio pulse would, with suitable particle physics^3,4, be much easier to detect than the γ-ray pulses that might also accompany the explosion⁵. The best published upper limit on the frequency of such γ-ray pulses is 4 × 10⁻² events pc⁻³ yr⁻¹ (ref. 6). We present here the results of a radio frequency search for isolated pulses, with much higher sensitivity than achieved previously. No definitive pulses have been detected, and the implied limit on PBH explosions is 2×10⁻⁹ events pc⁻³ yr⁻¹.