Relativistic collapse and explosion of rotating supermassive stars with thermonuclear effects

The Astrophysical Journal (Impact Factor: 6.28). 08/2011; 749(1). DOI: 10.1088/0004-637X/749/1/37
Source: arXiv

ABSTRACT We present results of general relativistic simulations of collapsing
supermassive stars with and without rotation using the two-dimensional general
relativistic numerical code Nada, which solves the Einstein equations written
in the BSSN formalism and the general relativistic hydrodynamics equations with
high resolution shock capturing schemes. These numerical simulations use an
equation of state which includes effects of gas pressure, and in a tabulated
form those associated with radiation and the electron-positron pairs. We also
take into account the effect of thermonuclear energy released by hydrogen and
helium burning. We find that objects with a mass of 5x10^{5} solar mass and an
initial metallicity greater than Z_{CNO}~0.007 do explode if non-rotating,
while the threshold metallicity for an explosion is reduced to Z_{CNO}~0.001
for objects uniformly rotating. The critical initial metallicity for a
thermonuclear explosion increases for stars with mass ~10^{6} solar mass. For
those stars that do not explode we follow the evolution beyond the phase of
black hole formation. We compute the neutrino energy loss rates due to several
processes that may be relevant during the gravitational collapse of these
objects. The peak luminosities of neutrinos and antineutrinos of all flavors
for models collapsing to a BH are ~10^{55} erg/s. The total radiated energy in
neutrinos varies between ~10^{56} ergs for models collapsing to a BH, and
~10^{45}-10^{46} ergs for models exploding.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper we explore a possible route of black hole seed formation that appeal to a model by Davies, Miller & Bellovary who considered the case of the dynamical collapse of a dense cluster of stellar black holes subjected to an inflow of gas. Here, we explore this case in a broad cosmological context. The working hypotheses are that (i) nuclear star clusters form at high redshifts in pre-galactic discs hosted in dark matter halos, providing a suitable environment for the formation of stellar black holes in their cores, (ii) major central inflows of gas occur onto these clusters due to instabilities seeded in the growing discs and/or to mergers with other gas-rich halos, and that (iii) following the inflow, stellar black holes in the core avoid ejection due to the steepening to the potential well, leading to core collapse and the formation of a massive seed of $<~ 1000\, \rm M_\odot$. We simulate a cosmological box tracing the build up of the dark matter halos and there embedded baryons, and explore cluster evolution with a semi-analytical model. We show that this route is feasible, peaks at redshifts $z <~ 10$ and occurs in concomitance with the formation of seeds from other channels. The channel is competitive relative to others, and is independent of the metal content of the parent cluster. This mechanism of gas driven core collapse requires inflows with masses at least ten times larger than the mass of the parent star cluster, occurring on timescales shorter than the evaporation/ejection time of the stellar black holes from the core. In this respect, the results provide upper limit to the frequency of this process.
    Monthly Notices of the Royal Astronomical Society 06/2014; 442(4). DOI:10.1093/mnras/stu1120 · 5.23 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Dark Stars (DS) are stellar objects made (almost entirely) of ordinary atomic material but powered by the heat from Dark Matter (DM) annihilation (rather than by fusion). Weakly Interacting Massive Particles (WIMPs), among the best candidates for DM, can be their own antimatter and can accumulate inside the star, with their annihilation products thermalizing with and heating the DS. The resulting DSs are in hydrostatic and thermal equilibrium. The first phase of stellar evolution in the history of the Universe may have been dark stars. Though DM constituted only $<0.1\%$ of the mass of the star, this amount was sufficient to power the star for millions to billions of years. Depending on their DM environment, early DSs can become very massive ($>10^6 M_\odot$), very bright ($>10^9 L_\odot$), and potentially detectable with the James Webb Space Telescope (JWST). Once the DM runs out and the dark star dies, it may collapse to a black hole; thus DSs can provide seeds for the supermassive black holes observed throughout the Universe and at early times. Other sites for dark star formation exist in the Universe today in regions of high dark matter density such as the centers of galaxies. The current review briefly discusses DSs existing today but focuses on the early generation of dark stars.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We study the Initial Mass Function (IMF) and host halo properties of Intermediate Mass Black Holes (IMBH, 10^{4-6} Msun) formed inside metal-free, UV illuminated atomic cooling haloes (virial temperature T_vir > 10^4 K) either via the direct collapse of the gas or via an intermediate Super Massive Star (SMS) stage. We achieve this goal in three steps: (a) we derive the gas accretion rate for a proto-SMS to undergo General Relativity instability and produce a direct collapse black hole (DCBH) or to enter the ZAMS and later collapse into a IMBH; (b) we use merger-tree simulations to select atomic cooling halos in which either a DCBH or SMS can form and grow, accounting for metal enrichment and major mergers that halt the growth of the proto-SMS by gas fragmentation. We derive the properties of the host halos and the mass distribution of black holes at this stage, and dub it the "Birth Mass Function"; (c) we follow the further growth of the DCBH due to accretion of leftover gas in the parent halo and compute the final IMBH mass.We consider two extreme cases in which minihalos (T_vir < 10^4 K) can (fertile) or cannot (sterile) form stars and pollute their gas leading to a different IMBH IMF. In the (fiducial) fertile case the IMF is bimodal extending over a broad range of masses, M= (0.5-20)x10^5 Msun, and the DCBH accretion phase lasts from 10 to 100 Myr. If minihalos are sterile, the IMF spans the narrower mass range M= (1-2.8)x10^6 Msun, and the DCBH accretion phase is more extended (70-120 Myr). We conclude that a good seeding prescription is to populate halos (a) of mass 7.5 < log (M_h/Msun) < 8, (b) in the redshift range 8 < z < 17, (c) with IMBH in the mass range 4.75 < log (M_BH/Msun) < 6.25.
    Monthly Notices of the Royal Astronomical Society 06/2014; 443(3). DOI:10.1093/mnras/stu1280 · 5.23 Impact Factor

Full-text (2 Sources)

Available from
May 30, 2014