Constraining the spin and the deformation parameters from the black hole shadow

By N. Tsukamoto, Zilong Li, Cosimo Bambi. 2014

204 citations recorded by the source corpus.

Within 5–10 years, very-long baseline interferometry (VLBI) facilities will be able to directly image the accretion flow around SgrA*, the super-massive black hole candidate at the center of the Galaxy, and observe the black hole ``shadow''. In 4-dimensional general relativity, the no-hair theorem asserts that uncharged black holes are described by the Kerr solution and are completely specified by their mass M and by their spin parameter a. In this paper, we explore the possibility of distinguishing Kerr and Bardeen black holes from their shadow. In Hioki & Maeda (2009), under the assumption that the background geometry is described by the Kerr solution, the authors proposed an algorithm to estimate the value of a/M by measuring the distortion parameter δ, an observable quantity that characterizes the shape of the shadow. Here, we try to extend their approach. Since the Hioki-Maeda distortion parameter is degenerate with respect to the spin and possible deviations from the Kerr solution, one has to measure another quantity to test the Kerr black hole hypothesis. We study a few possibilities. We find that it is extremely difficult to distinguish Kerr and Bardeen black holes from the sole observation of the shadow, and out of reach for the near future. The combination of the measurement of the shadow with possible accurate radio observations of a pulsar in a compact orbit around SgrA* could be a more promising strategy to verify the Kerr black hole paradigm.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/7c9eb86cb74ccdfa63128d8a0b3dc1ca80202610

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Citations in the corpus

Gravitational Lensing in Presence of Plasma: Strong Lens Systems, Black Hole Lensing and Shadow (2017, background): “Numerous analytical investigations and numerical simulations of the shadow are presented in literature (for example, see [90, 101, 95, 85, 86, 103, 104, 105, 94, 98, 99, 91, 106, 102, 97, 87, 88, 89, 93, 92, 96, 100, 110, 107, 108, 109, 111]).”
Testing black hole candidates with electromagnetic radiation (2015, unknown): “…& Eiroa, 2012, 2013; Amarilla et al., 2010; Atamurotov et al., 2013a,b; Bambi, 2013f; Bambi et al., 2012; Bambi & Freese, 2009; Bambi & Yoshida, 2010; Ghasemi-Nodehi et al., 2015; Johannsen & Psaltis, 2010; Li & Bambi, 2014a; Schee & Stuchĺık, 2009; Tsukamoto et al., 2014; Wei & Liu, 2013).”
A coordinate-independent characterization of a black hole shadow (2015, background): “…in known space-times, either within general relativity (Young 1976; Perlick 2004; Abdujabbarov et al. 2013), or within alternative theories of gravity (Bambi & Modesto 2013; Tsukamoto et al. 2014; Amarilla et al. 2010; Amarilla & Eiroa 2012, 2013; Atamurotov et al. 2013a,b; Schee & Stuchlı́k 2009).”