Stars and halos of degenerate relativistic heavy-neutrino and neutralino matter

Abstract

Heavy-neutrino (or neutralino) stars are studied using the general relativistic equations of hydrostatic equilibrium and the relativistic equation of state for degenerate fermionic matter. The Tolman-Oppenheimer-Volkoff equations are then generalized to include a system of degenerate neutrino and neutralino matter that is gravitationally coupled. The properties and implications of such an interacting astrophysical system are discussed in detail. 04.40.Dg, 97.20.Rp, 95.35.+d, 97.60.Jd, 98.35.Jk

Comparison of the Black Hole and Fermion Ball Scenarios of the Galactic Center

“…The dynamics of the stars in the gravitational field of the supermassive compact dark object can be studied solving Newton's equation of motion, taking into account the initial position and velocity vectors at, e.g., t 0 = 1995.4 yr, i.e., r(t 0 ) ≡ (x, y, z) and˙ r(t 0 ) ≡ (v x , v y , v z ). For the fermion ball the source of gravitational field is the mass M(r) enclosed within a radius r [4,6] while for the black hole it is M c = M(R c ) = 2.6 × 10 6 M ⊙ . The x-axis is chosen in the direction opposite to the right ascension (RA), the y-axis in the direction of the declination, and the z-axis points towards the sun.…”

“…More recently, supermassive compact dark objects consisting of weakly interacting degenerate fermionic matter, with fermion masses in the 10 ∼ < m/keV ∼ < 20 range, have been proposed [2,3,4,5,6] as an alternative to the supermassive black holes that are believed to reside at the centers of many galaxies. The masses of ∼ 20 supermassive compact dark objects at the centers of inactive galaxies [7] have been measured so far.…”

“…If we identify the object of maximal mass with a degenerate fermion ball at the Oppenheimer-Volkoff (OV) limit [9], i.e. M OV = 0.54M 3 Pl m −2 g −1/2 ≃ 3 × 10 9 M ⊙ [4], where M Pl = hc/G, this allows us to fix the fermion mass to ≃ 15 keV for a spin and particle-antiparticle degeneracy factor of g = 2. Such a relativistic object would have a radius of R OV = 4.45 R S ≃ 1.5 light days, where R S is the Schwarzschild radius of the mass M OV .…”

On the formation of degenerate heavy neutrino stars

“…Interpreting this object as a relativistic fermion star at the Oppenheimer-Volkoff [8] limit, yields a fermion mass of m f ≃ 15 keV and a fermion star radius of R = 4.45R S ≃ 1.5 light-days [3,4], where R S is the Schwarzschild radius. In this case there is little difference between the fermion star and black hole scenarios, because the radius of the last stable orbit around a Schwarzschild black hole is R = 3R S anyway.…”

“…Originally, these objects were proposed as models for dark matter in galactic halos and clusters of galaxies, with neutrino masses in the ∼ eV range. More recently, however, degenerate superstars composed of weakly interacting fermions in the ∼ 10 keV range, have been suggested as an alternative to the supermassive black holes that are purported to exist at the centers of galaxies [2][3][4][5][6]. In fact, it has been shown [4] that such degenerate fermion stars could explain the whole range of supermassive compact dark objects which have been observed so far, with masses ranging from 10 6 to 3 × 10 9 M ⊙ , merely assuming that a weakly interacting quasi-stable fermion of mass m f ≃ 15 keV exists in nature.…”