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 Shadows of Einstein-dilaton-Gauss-Bonnet black holes
Please use this identifier to cite or link to this item http://hdl.handle.net/10773/18259

title: Shadows of Einstein-dilaton-Gauss-Bonnet black holes
authors: Cunha, P. V. P.
Herdeiro, C. A. R.
Kleihaus, B.
Kunz, J.
Radu, E.
issue date: 2017
publisher: Elsevier
abstract: We study the shadows of the fully non-linear, asymptotically flat Einstein-dilaton-Gauss-Bonnet (EdGB) black holes (BHs), for both static and rotating solutions. We find that, in all cases, these shadows are smaller than for comparable Kerr BHs, i.e. with the same total mass and angular momentum under similar observation conditions. In order to compare both cases we provide quantitative shadow parameters, observing in particular that the differences in the shadows mean radii are never larger than the percent level. Therefore, generically, EdGB BHs cannot be excluded by (near future) shadow observations alone. On the theoretical side, we find no clear signature of some exotic features of EdGB BHs on the corresponding shadows, such as the regions of negative (Komar, say) energy density outside the horizon. We speculate that this is due to the fact that the Komar energy interior to the light rings (or more precisely, the surfaces of constant radial coordinate that intersect the light rings in the equatorial plane) is always smaller than the ADM mass, and consequently the corresponding shadows are smaller than those of comparable Kerr BHs. The analysis herein provides a clear example that it is the light ring impact parameter, rather than its "size", that determines a BH shadow. (C) 2017 The Authors. Published by Elsevier B.V.
URI: http://hdl.handle.net/10773/18259
ISSN: 0370-2693
publisher version/DOI: https://doi.org/10.1016/j.physletb.2017.03.020
source: Physics Letters B
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