| 1. |
- Asplund, Martin, et al.
(författare)
-
The Chemical Composition of the Sun
- 2009
-
Ingår i: Annual Review of Astronomy and Astrophysics. - : Annual Reviews. - 0066-4146 .- 1545-4282. ; 47, s. 481-522
-
Forskningsöversikt (refereegranskat)abstract
- The solar chemical composition is an important ingredient in our understanding of the formation, structure, and evolution of both the Sun and our Solar System. Furthermore, it is an essential reference standard against which the elemental contents of other astronomical objects are compared. In this review, we evaluate the current understanding of the solar photospheric composition. In particular, we present a redetermination of the abundances of nearly all available elements, using a realistic new three-dimensional (3D), time-dependent hydrodynamical model of the solar atmosphere. We have carefully considered the atomic input data and selection of spectral lines, and accounted for departures from local thermodynamic equilibrium (LTE) whenever possible. The end result is a comprehensive and homogeneous compilation of the solar elemental abundances. Particularly noteworthy findings are significantly lower abundances of C, N, O, and Ne compared to the widely used values of a decade ago. The new solar chemical composition is supported by a high degree of internal consistency between available abundance indicators, and by agreement with values obtained in the Solar Neighborhood and from the most pristine meteorites. There is, however, a stark conflict with standard models of the solar interior according to helio-seismology, a discrepancy that has yet to find a satisfactory resolution.
|
|
| 2. |
- Scott, Pat, et al.
(författare)
-
Gamma Rays from Ultracompact Primordial Dark Matter Minihalos
- 2009
-
Ingår i: Physical Review Letters. - : The American Physical Society. - 0031-9007 .- 1079-7114. ; 103:21, s. 211301-1-211301-4
-
Tidskriftsartikel (refereegranskat)abstract
- Ultracompact minihalos have been proposed as a new class of dark matter structure. They would be produced by phase transitions in the early Universe or features in the inflaton potential, and constitute nonbaryonic massive compact halo objects today. We examine the prospects of detecting these minihalos in gamma rays if dark matter can self-annihilate. We compute present-day fluxes from minihalos produced in the e(+)e(-) annihilation epoch and the QCD and electroweak phase transitions. Even at a distance of 4 kpc, minihalos from the e(+)e(-) epoch would be eminently detectable today by the Fermi satellite or air Ccerenkov telescopes, or even in archival EGRET data. Within 2 kpc, they would appear as extended sources to Fermi. At 4 kpc, minihalos from the QCD transition have similar predicted fluxes to dwarf spheroidal galaxies, so might also be detectable by present or upcoming experiments.
|
|
| 3. |
- Scott, Pat, et al.
(författare)
-
Impacts of WIMP dark matter upon stellar evolution : main-sequence stars
- 2008
-
Ingår i: Identification of dark matter 2008. ; , s. 73-
-
Konferensbidrag (refereegranskat)abstract
- The presence of large amounts of WIMP dark matter in stellar cores has been shown to have significant effects upon models of stellar evolution. We present a series of detailed grids of WIMPinfluenced stellar models for main sequence stars, computed using the DarkStars code. We describe the changes in stellar structure and main sequence evolution which occur for masses ranging from 0.3 to 2.0 M and metallicities from Z = 0:0003–0: 02, as a function of the rate of energy injection by WIMPs. We then go on to show what rates of energy injection can beobtained using realistic orbital parameters for stars near supermassive black holes, including detailed considerations of dark matter halo velocity and density profiles. Capture and annihilation rates are strongly boosted when stars follow elliptical rather than circular orbits, causing WIMP annihilation to provide up to 100 times the energy of hydrogen fusion in stars at the Galactic centre
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
