7 research outputs found
Dark Stars: A New Study of the FIrst Stars in the Universe
We have proposed that the first phase of stellar evolution in the history of
the Universe may be Dark Stars (DS), powered by dark matter heating rather than
by nuclear fusion. Weakly Interacting Massive Particles, which may be their own
antipartners, collect inside the first stars and annihilate to produce a heat
source that can power the stars. A new stellar phase results, a Dark Star,
powered by dark matter annihilation as long as there is dark matter fuel, with
lifetimes from millions to billions of years. We find that the first stars are
very bright () and cool (K) during the DS
phase, and grow to be very massive (500-1000 times as massive as the Sun).
These results differ markedly from the standard picture in the absence of DM
heating, in which the maximum mass is about 140 and the temperatures
are much hotter (K); hence DS should be observationally
distinct from standard Pop III stars. Once the dark matter fuel is exhausted,
the DS becomes a heavy main sequence star; these stars eventually collapse to
form massive black holes that may provide seeds for supermassive black holes
observed at early times as well as explanations for recent ARCADE data and for
intermediate black holes.Comment: article to be published in special issue on Dark Matter and Particle
Physics in New Journal of Physic
Dark Matter Capture in the First Stars: a Power Source and Limit on Stellar Mass
The annihilation of weakly interacting massive particles can provide an
important heat source for the first (Pop. III) stars, potentially leading to a
new phase of stellar evolution known as a "Dark Star". When dark matter (DM)
capture via scattering off of baryons is included, the luminosity from DM
annihilation may dominate over the luminosity due to fusion, depending on the
DM density and scattering cross-section. The influx of DM due to capture may
thus prolong the lifetime of the Dark Stars. Comparison of DM luminosity with
the Eddington luminosity for the star may constrain the stellar mass of zero
metallicity stars; in this case DM will uniquely determine the mass of the
first stars. Alternatively, if sufficiently massive Pop. III stars are found,
they might be used to bound dark matter properties.Comment: 19 pages, 4 figures, 3 Tables updated captions and graphs, corrected
grammer, and added citations revised for submission to JCA
Compatibility of DAMA/LIBRA dark matter detection with other searches in light of new Galactic rotation velocity measurements
The DAMA/NaI and DAMA/LIBRA annual modulation data, which may be interpreted
as a signal for the existence of weakly interacting dark matter (WIMPs) in our
galactic halo, are re-examined in light of new measurements of the local
velocity relative to the galactic halo. In the vicinity of the Sun, the
velocity of the Galactic disk has been estimated to be 250 km/s rather than 220
km/s. Our analysis is performed both with and without the channeling effect
included. The best fit regions to the DAMA data are shown to move to slightly
lower WIMP masses. Compatibility of DAMA data with null results from other
experiments (CDMS, XENON10, and CRESST I) is investigated given these new
velocities. A small region of spin-independent (elastic) scattering for 7-8 GeV
WIMP masses remains at 3. Spin-dependent scattering off of protons is
viable for 5-15 GeV WIMP masses for direct detection experiments (but has been
argued by others to be further constrained by Super-Kamiokande due to
annihilation in the Sun).Comment: 18 pages, 6 figures. v2: added reference, minor changes to match JCAP
versio
Dark Stars and Boosted Dark Matter Annihilation Rates
Dark Stars (DS) may constitute the first phase of stellar evolution, powered
by dark matter (DM) annihilation. We will investigate here the properties of DS
assuming the DM particle has the required properties to explain the excess
positron and elec- tron signals in the cosmic rays detected by the PAMELA and
FERMI satellites. Any possible DM interpretation of these signals requires
exotic DM candidates, with an- nihilation cross sections a few orders of
magnitude higher than the canonical value required for correct thermal relic
abundance for Weakly Interacting Dark Matter can- didates; additionally in most
models the annihilation must be preferentially to lep- tons. Secondly, we study
the dependence of DS properties on the concentration pa- rameter of the initial
DM density profile of the halos where the first stars are formed. We restrict
our study to the DM in the star due to simple (vs. extended) adiabatic
contraction and minimal (vs. extended) capture; this simple study is sufficient
to illustrate dependence on the cross section and concentration parameter. Our
basic results are that the final stellar properties, once the star enters the
main sequence, are always roughly the same, regardless of the value of boosted
annihilation or concentration parameter in the range between c=2 and c=5:
stellar mass ~ 1000M\odot, luminosity ~ 10^7 L\odot, lifetime ~ 10^6 yrs (for
the minimal DM models considered here; additional DM would lead to more massive
dark stars). However, the lifetime, final mass, and final luminosity of the DS
show some dependence on boost factor and concentration parameter as discussed
in the paper.Comment: 37 pages, 11 figure
Dark Matter Candidates: A Ten-Point Test
An extraordinarily rich zoo of non-baryonic Dark Matter candidates has been
proposed over the last three decades. Here we present a 10-point test that a
new particle has to pass, in order to be considered a viable DM candidate: I.)
Does it match the appropriate relic density? II.) Is it {\it cold}? III.) Is it
neutral? IV.) Is it consistent with BBN? V.) Does it leave stellar evolution
unchanged? VI.) Is it compatible with constraints on self-interactions? VII.)
Is it consistent with {\it direct} DM searches? VIII.) Is it compatible with
gamma-ray constraints? IX.) Is it compatible with other astrophysical bounds?
X.) Can it be probed experimentally?Comment: 29 pages, 12 figure