Thin accretion disks around cold Bose–Einstein condensate stars

Abstract

Due to their superfluid properties some compact astrophysical objects, like neutron or quark stars, may contain a significant part of their matter in the form of a BoseEinstein condensate (BEC). Observationally distinguishing between neutron/quark stars and BEC stars is a major challenge for this latter theoretical model. An observational possibility of indirectly distinguishing BEC stars from neutron/quark stars is through the study of the thin accretion disks around compact general relativistic objects. In the present paper, we perform a detailed comparative study of the electromagnetic and thermodynamic properties of the thin accretion disks around rapidly rotating BEC stars, neutron stars and quark stars, respectively. Due to the differences in the exterior geometry, the thermodynamic and electromagnetic properties of the disks (energy flux, temperature distribution, equilibrium radiation spectrum, and efficiency of energy conversion) are different for these classes of compact objects. Hence in this preliminary study we have pointed out some astrophysical signatures that may allow one to observationally discriminate between BEC stars and neutron/quark stars.

Compact stars admitting Finch-Skea symmetry in the presence of various matter fields*

“…Finally, some studies addressed the field of Bose-Einstein condensate stars, generally adopting hydrodynamical representations for the BEC wave function and using polytropic Equation of State. For example, BEC stars were investigated in [17][18][19].…”

Thin accretion disk onto slowly rotating black holes in Einstein-Æther theory

“…For an astrophysical black hole, the study of the electromagnetic spectrum from the accretion process around the black hole is a powerful approach to explore the nature of the black hole spacetime in the regime of strong gravity. This has stimulated a lot works on the studies of the thin accretion disk around various black hole spacetimes, see [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] and references therein. Therefore, it is natural to ask whether the aether field corrections of the Einstein-AEther theory can appear in the electromagnetic signatures and the optical appearance to a distant observer of the accretion disk.…”

Accretion disks around neutron and strange stars inR+aR2gravity

“…General Relativistic temperature profiles and spectra from a thin accretion disk around neutron stars are calculated in [7][8][9][10], and temperature profiles of accretion disks around strange stars are calculated in [11]. The electromagnetic properties of the accretion disk around neutron, strange and boson stars and comments on the possibility of determining the nature of the central object from the disk's spectrum are made in [12] and [13]. The emissivity properties of a thin accretion disk have been investigated for more exotic compact objects, too.…”