Astrophysical imaging of Kerr black holes with scalar hair

Vincent, F.; Gourgoulhon, Éric; Herdeiro, Carlos; Radu, Eugen

doi:10.1103/physrevd.94.084045

Cited by 97 publications

(91 citation statements)

References 47 publications

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“…3 shows the iron line profile for the solutions 2 and 4, varying also the inner edge of the accretion disk r in (we consider a disk truncated as in Refs. [21,94]). The solutions 1 and 3 are quite similar to the solution 2, while the solution 5 is similar to the solution 4.…”

Section: Iron Kα Linementioning

confidence: 99%

Iron Kα line of boson stars

Cao

Cárdenas-Avendaño

Zhou

et al. 2016

J. Cosmol. Astropart. Phys.

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Abstract. The present paper is a sequel to our previous work [Y. Ni et al., JCAP 1607, 049 (2016] in which we studied the iron Kα line expected in the reflection spectrum of Kerr black holes with scalar hair. These metrics are solutions of Einstein's gravity minimally coupled to a massive, complex scalar field. They form a continuous bridge between a subset of Kerr black holes and a family of rotating boson stars depending on one extra parameter, the dimensionless scalar hair parameter q, ranging from 0 (Kerr black holes) to 1 (boson stars). Here we study the limiting case q = 1, corresponding to rotating boson stars. For comparison, spherical boson stars are also considered. We simulate observations with XIS/Suzaku. Using the fact that current observations are well fit by the Kerr solution and thus requiring that acceptable alternative compact objects must be compatible with a Kerr fit, we find that some boson star solutions are relatively easy to rule out as potential candidates to explain astrophysical black holes, while other solutions, which are neither too dilute nor too compact are more elusive and we argue that they cannot be distinguished from Kerr black holes by the analysis of the iron line with current X-ray facilities.

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Section: Iron Kα Linementioning

confidence: 99%

Iron Kα line of boson stars

Cao

Cárdenas-Avendaño

Zhou

et al. 2016

J. Cosmol. Astropart. Phys.

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“…For the rotating case, the shadow has an elongated shape in the direction of the rotation axis due to the dragging effect [2,3]. Motivated by that the investigation of the shadow is very useful for measuring the nature of the black hole and the corresponding observations may be obtained in the near future, a lot of attention have been attracted on this subject in the last few years [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Double shadow of a regular phantom black hole as photons couple to the Weyl tensor

2016

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We have studied the shadow of a regular phantom black hole as photons couple to the Weyl tensor. We find that due to the coupling photons with different polarization directions propagate along different paths in the spacetime so that there exists a double shadow for a black hole, which is quite different from that in the non-coupling case where only a single shadow emerges. The overlap region of the double shadow, the umbra, of the black hole increases with the phantom charge and decreases with the coupling strength. The dependence of the penumbra on the phantom charge and the coupling strength is converse to that of the umbra. Combining with the supermassive central object in our Galaxy, we estimated the shadow of the black hole as the photons couple to the Weyl tensor. Our results show that the coupling brings about richer behaviors of the propagation of coupled photon and the shadow of the black hole in the regular phantom black hole spacetime.

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“…In a recent paper [12], some of us have studied the lensing and shadows of a deformed type of Kerr BHs, known as Kerr BHs with scalar hair (KBHsSH) [54][55][56] (see also [57][58][59][60][61][62][63][64][65][66][67][68][69][70][71] for generalizations and physical properties). These are solutions to Einstein's gravity minimally coupled to a simple and physically reasonable matter content: a complex, massive, free scalar field.…”

Section: Introductionmentioning

confidence: 99%

Chaotic lensing around boson stars and Kerr black holes with scalar hair

et al. 2016

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In a recent paper [P. V. P. Cunha, C. A. R. Herdeiro, E. Radu, and H. F. Runarsson, Phys. Rev. Lett. 115, 211102 (2015).], it was shown that the lensing of light around rotating boson stars and Kerr black holes with scalar hair can exhibit chaotic patterns. Since no separation of variables is known (or expected) for geodesic motion on these backgrounds, we examine the 2D effective potentials for photon trajectories, to obtain a deeper understanding of this phenomenon. We find that the emergence of stable light rings on the background spacetimes allows the formation of "pockets" in one of the effective potentials, for open sets of impact parameters, leading to an effective trapping of some trajectories, dubbed "quasibound orbits." We conclude that pocket formation induces chaotic scattering, although not all chaotic orbits are associated to pockets. These and other features are illustrated in a gallery of examples, obtained with a new ray-tracing code, PYHOLE, which includes tools for a simple, simultaneous visualization of the effective potential, together with the spacetime trajectory, for any given point in a lensing image. An analysis of photon orbits allows us to further establish a positive correlation between photon orbits in chaotic regions and those with more than one turning point in the radial direction; we recall that the latter is not possible around Kerr black holes. Moreover, we observe that the existence of several light rings around a horizon (several fundamental orbits, including a stable one), is a central ingredient for the existence of multiple shadows of a single hairy black hole. We also exhibit the lensing and shadows by Kerr black holes with scalar hair, observed away from the equatorial plane, obtained with PYHOLE.

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Astrophysical imaging of Kerr black holes with scalar hair

Cited by 97 publications

References 47 publications

Iron Kα line of boson stars

Iron Kα line of boson stars

Double shadow of a regular phantom black hole as photons couple to the Weyl tensor

Chaotic lensing around boson stars and Kerr black holes with scalar hair

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