Evidence for the Black Hole Event Horizon

TL;DR

The paper argues that the absence of Type I X-ray bursts in black hole candidates provides strong evidence for the existence of event horizons, distinguishing black holes from neutron stars.

Contribution

It proposes a novel method using the absence of X-ray bursts to confirm the presence of event horizons in black hole candidates.

Findings

Black hole candidates do not exhibit Type I X-ray bursts.

Model calculations suggest that if black holes had surfaces, bursts would be frequent.

The lack of bursts supports the existence of event horizons in black holes.

Abstract

Roughly a dozen X-ray binaries are presently known in which the compact accreting primary stars are too massive to be neutron stars. These primaries are identified as black holes, though there is as yet no definite proof that any of the candidate black holes actually possesses an event horizon. We discuss how Type I X-ray bursts may be used to verify the presence of the event horizon in these objects. Type I bursts are caused by thermonuclear explosions when gas accretes onto a compact star. The bursts are commonly seen in many neutron star X-ray binaries, but they have never been seen in any black hole X-ray binary. Our model calculations indicate that black hole candidates ought to burst frequently if they have surfaces. Based on this, we argue that the lack of bursts constitutes strong evidence for the presence of event horizons in these objects.