Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 0711.2039

Fine Grid Asteroseismology of R548 and G117-B15A

A. Bischoff-Kim·M. H. Montgomery·D. E. Winget
View original source ↗Read source document ↗Export metadata ↓

Abstract

We now have a good measurement of the cooling rate of G117-B15A. In the near future, we will have equally well determined cooling rates for other pulsating white dwarfs, including R548. The ability to measure their cooling rates offers us a unique way to study weakly interacting particles that would contribute to their cooling. Working toward that goal, we perform a careful asteroseismological analysis of G117-B15A and R548. We study them side by side because they have similar observed properties. We carry out a systematic, fine grid search for best fit models to the observed period spectra of those stars. We freely vary 4 parameters: the effective temperature, the stellar mass, the helium layer mass, and the hydrogen layer mass. We identify and quantify a number of uncertainties associated with our models. Based on the results of that analysis and fits to the periods observed in R548 and G117-B15A, we clearly define the regions of the 4 dimensional parameter space ocuppied by the best fit models.

Explore related subjects

astro-ph

Keep this discovery

BibTeXRIS

A. Bischoff-Kim, M. H. Montgomery, D. E. Winget. 2007-11-13. Fine Grid Asteroseismology of R548 and G117-B15A. https://doi.org/10.1086/527287

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2018

The Outward Radial Offset of Neptune Ring Arcs

The designation of the customary restricted three-body disturbing potential $Φ$ as the perturbation Hamiltonian is believed to be the cause of Neptune ring arcs' radial offset between theories and observations. To identify the appropriate perturbation Hamiltonian, the energy integral in the fixed frame of a restricted three-body system, consisting of the central, primary, and test bodies, is reconsidered. It is shown that the perturbation energy includes the disturbing potential $Φ$ and the potential arising from the angular momentum terms of the test body. Both potentials happen to be singular as the test body goes to infinity contradicting to the perturbation nature. These two potentials can be combined to an energy relevant disturbing potential $Φ^{*}=βΦ$ which is regular at infinity because of the cancellation of the singularities. For circular orbits of the primary, the energy equation is conservative, and $Φ^{*}$ is identified as the perturbation Hamiltonian. Applying this result to evaluate the backgrund effect of Triton to the arc-Galatea system of Neptune, it is shown that there is a small difference $ΔΦ=(Φ^{*}-Φ)$ which amounts to an outward radial offset of the corotation location of Galatea by 0.3 Km. The mismatch between the pattern speed of Galatea's corotation potential and the mean motion velocity of the arcs could be resolved by considering the finite mass of Fraternite. However, by using $Φ^{*}$, Galatea's eccentricity could be reassessed in terms of the mass of Fraternite.

astro-ph↗
arXiv2018

Nuclear Reaction Network for Primordial Nucleosynthesis: a detailed analysis of rates, uncertainties and light nuclei yields

We analyze in details the standard Primordial Nucleosynthesis scenario. In particular we discuss the key theoretical issues which are involved in a detailed prediction of light nuclide abundances, as the weak reaction rates, neutrino decoupling and nuclear rate modeling. We also perform a new analysis of available data on the main nuclear processes entering the nucleosynthesis reaction network, with particular stress on their uncertainties as well as on their role in determining the corresponding uncertainties on light nuclide theoretical estimates. The current status of theoretical versus experimental results for 2H, 3He, 4He and 7Li is then discussed using the determination of the baryon density as obtained from Cosmic Microwave Background anisotropies.

astro-ph↗
arXiv2018

Sky coverage of orbital detectors. Analytical approach

Orbital detectors without pointing capability have to keep their field of view axis laying on their orbital plane, to observe the largest sky fraction. A general approach to estimate the exposure of each sky element for such detectors is a valuable tool in the R&D phase of a project, when the detector characteristics are still to be fixed. An analytical method to estimate the sky exposure is developed, which makes only few very reasonable approximations. The formulae obtained with this method are used to compute the histogram of the sky exposure of a hypothetical gamma-ray detector installed on the ISS. The C++ code used in this example is freely available on the https://github.com/dcasadei/SkyCoverage web page.

astro-ph↗