Infrared observations of Sgr A* and M87* are incompatible with the assumption that these sources have physical surfaces in thermal equilibrium with their accreting environments. In this paper we discuss a general parametrization of the energy balance in a horizonless object, which permits to quantify how close a horizonless object is in its behavior to a black hole, and analyze the timescale in which its surface can thermalize. We show that the thermalization timescale is unbounded, growing large for objects that mimic closely the behavior of a black hole (and being infinite for the latter). In particular, the thermalization timescale is proportional to the time that energy spends inside the horizonless object due to propagation and interactions with the bulk. Hence, these observations can be used to quantitatively restrict the dynamical behavior of horizonless objects, without being able to discard the existence of a physical surface.

Constraints on thermalizing surfaces from infrared observations of supermassive black holes / Carballo-Rubio, R.; Di Filippo, F.; Liberati, S.; Visser, M.. - In: JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS. - ISSN 1475-7516. - 118:(2023), pp. 1-16. [10.1088/1475-7516/2023/11/041]

Constraints on thermalizing surfaces from infrared observations of supermassive black holes

Di Filippo, F.;Liberati, S.;
2023-01-01

Abstract

Infrared observations of Sgr A* and M87* are incompatible with the assumption that these sources have physical surfaces in thermal equilibrium with their accreting environments. In this paper we discuss a general parametrization of the energy balance in a horizonless object, which permits to quantify how close a horizonless object is in its behavior to a black hole, and analyze the timescale in which its surface can thermalize. We show that the thermalization timescale is unbounded, growing large for objects that mimic closely the behavior of a black hole (and being infinite for the latter). In particular, the thermalization timescale is proportional to the time that energy spends inside the horizonless object due to propagation and interactions with the bulk. Hence, these observations can be used to quantitatively restrict the dynamical behavior of horizonless objects, without being able to discard the existence of a physical surface.
2023
118
1
16
041
10.1088/1475-7516/2023/11/041
https://arxiv.org/abs/2306.17480
Carballo-Rubio, R.; Di Filippo, F.; Liberati, S.; Visser, M.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11767/135186
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