Can accretion disk properties distinguish gravastars from black holes?

TL;DR

This study explores how accretion disk properties around rotating gravastars differ from those around black holes, offering potential observational signatures to distinguish these hypothetical objects.

Contribution

The paper provides a detailed analysis of accretion disk properties around slowly rotating gravastars, highlighting differences from black holes that could be used for observational distinction.

Findings

Accretion disk energy flux, temperature, and spectrum differ between gravastars and black holes.

Conversion efficiency of mass to radiation is lower for gravastars.

Distinct electromagnetic signatures can help differentiate gravastars from black holes.

Abstract

Gravastars, hypothetic astrophysical objects, consisting of a dark energy condensate surrounded by a strongly correlated thin shell of anisotropic matter, have been proposed as an alternative to the standard black hole picture of general relativity. Observationally distinguishing between astrophysical black holes and gravastars is a major challenge for this latter theoretical model. In the context of stationary and axially symmetrical geometries, a possibility of distinguishing gravastars from black holes is through the comparative study of thin accretion disks around rotating gravastars and Kerr-type black holes, respectively. In the present paper, we consider accretion disks around slowly rotating gravastars, with all the metric tensor components estimated up to the second order in the angular velocity. Due to the differences in the exterior geometry, the thermodynamic and electromagnetic properties of the disks (energy flux, temperature distribution and equilibrium radiation spectrum) are different for these two classes of compact objects, consequently giving clear observational signatures. In addition to this, it is also shown that the conversion efficiency of the accreting mass into radiation is always smaller than the conversion efficiency for black holes, i.e., gravastars provide a less efficient mechanism for converting mass to radiation than black holes. Thus, these observational signatures provide the possibility of clearly distinguishing rotating gravastars from Kerr-type black holes.