Uncertainties In Abundances Research Articles

Imaging and spectroscopy of ejected common envelopes --

Imaging and spectroscopy are presented for four planetary nebulae known to contain close binary central stars resulting from a recent phase of common envelope evolution. These objects are Abell 41, Abell 46, Abell 63 and Abell 65. Determinations of the nebula abundances show that He is significantly enhanced in all of the objects. These results are in agreement with theoretical expectations. Uncertainties in the nebular electron temperature constrain other abundances less well. The line fluxes indicate that N is unexpectedly under-abundant. This effect is probably not real and may be an artifact of electron temperature fluctuations within the nebulae.

Imaging and spectroscopy of ejected common envelopes

Imaging and spectroscopy are presented for four planetary nebulae known to contain close binary central stars resulting from a recent phase of common envelope evolution. These objects are Abell 41, Abell 46, Abell 63 and Abell 65. Determinations of the nebula abundances show that He is significantly enhanced in all of the objects. These results are in agreement with theoretical expectations. Uncertainties in the nebular electron temperature constrain other abundances less well. The line fluxes indicate that N is unexpectedly under-abundant. This effect is probably not real and may be an artifact of electron temperature fluctuations within the nebulae.

Inhomogeneous Primordial Nucleosynthesis and New Abundance Constraints on Omega BH 2

view Abstract Citations (25) References (70) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Inhomogeneous Primordial Nucleosynthesis and New Abundance Constraints on Omega BH 2 Mathews, G. J. ; Kajino, T. ; Orito, M. Abstract We discuss the upper limit to the baryonic contribution to the closure density. We consider effects of new observational and theoretical uncertainties in the primordial light-element abundances and the effects of fluctuation geometry on the inhomogeneous nucleosynthesis yields. We also consider implications of the possible detection of a high D/H abundance in a Lyman-α absorption cloud at high redshift and the implied chemical evolution effects of a high deuterium abundance. We show that there exists a region of the parameter space for inhomogeneous models in which a somewhat higher baryonic contribution to the closure density is possible than that allowed in standard homogeneous models. This result is contrary to some other recent studies and is due to both geometry and recently revised uncertainties in primordial light-element abundances, particularly 7Li. We find that the presently adopted abundance constraints are consistent with a contribution of baryons to the closure density as high as Ωbh250 ≤ 0.11 (n ≤ 7 × 10-10). This corresponds to a 20% increase over the limit from standard homogeneous models (Ωbh250 ≤ 0.08, η ≤ 5.8 × 10-10). With a high deuterium abundance the upper limits for the inhomogeneous and homogeneous models would be Ωbh250 ≤ 0.04 and 0.03 (η ≤ 2.6 × 10-10 and 1.9 × 10-10), respectively. Even higher limits could be obtained by further relaxing the presently accepted primordial lithium abundance constraint as some have proposed. Publication: The Astrophysical Journal Pub Date: January 1996 DOI: 10.1086/176630 Bibcode: 1996ApJ...456...98M Keywords: COSMOLOGY: THEORY; COSMOLOGY: DARK MATTER; COSMOLOGY: EARLY UNIVERSE; NUCLEAR REACTIONS; NUCLEOSYNTHESIS; ABUNDANCES full text sources ADS |

Assessing Big-Bang nucleosynthesis.

Systematic uncertainties in the light-element abundances and their evolution complicate a rigorous statistical assessment. However, using Bayesian methods we show that the following statement is robust: The predicted and measured abundances are consistent with 95% credibility only if the baryon-to-photon ratio is between 2{times}10{sup {minus}10} and 6.5{times}10{sup {minus}10} and the number of light neutrino species is less than 3.9. Our analysis suggests that the {sup 4}He abundance may have been systematically underestimated. {copyright} {ital 1995} {ital The} {ital American} {ital Physical} {ital Society}.

A Lower Limit on the Age of the Universe

A detailed numerical study was designed and conducted to estimate the absolute age and the uncertainty in age (with confidence limits) of the oldest globular clusters in our galaxy, and hence to put a robust lower bound on the age of the universe. Estimates of the uncertainty range and distribution in the input parameters of stellar evolution codes were used to produce 1000 Monte Carlo realizations of stellar isochrones, which were then used to derive ages for the 17 oldest globular clusters. A probability distribution for the mean age of these systems was derived by incorporating the observational uncertainties in the measured color-magnitude diagrams for these systems and the predicted isochrones. The dominant contribution to the width of the distribution (approximately ± 5 percent) resulted from the observational uncertainty in RR-Lyrae variable absolute magnitudes. Subdominant contributions came from the choice of the color table used to translate theoretical luminosities and temperatures to observed magnitudes and colors, as well as from theoretical uncertainties in heavy element abundances and mixing length. The one-sided 95 percent confidence limit lower bound for this distribution occurs at an age of 12.07 × 10 9 years, and the median age for the distribution is 14.56 × 10 9 years. These age limits, when compared with the Hubble age estimate, put powerful constraints on cosmology.

Consistency of Cosmic-ray Source Abundances with Explosive Nucleosynthesis

SEVERAL studies1,2 have compared abundances of elements in the cosmic-ray sources (CRS) with Solar System (SS) abundances. Their results, however, are in general inconclusive because the uncertainties in the elemental abundances in both the CRS and the SS preclude the deduction of any systematic trend in the ratios of these two sets of abundances (CRS/SS). But, by limiting the comparison to elements for which the uncertainties are small (C, O, Mg, Si, Fe), we find that the values of CRS/SS are about 1 for Mg, Si and Fe and are significantly less than 1 for C and O. We do not wish to build a detailed theory on four independent data points. Nonetheless, this result could be explained if all CRS abundances were the same as those obtained from explosive nucleosynthesis3–5 and if the Solar System were enriched in C and O. Such a model is consistent with the fact that in the Solar System Mg, Si and Fe are believed to be produced by explosive nucleosynthesis, whereas C and O are mainly products of other processes (A. G. W. Cameron, to be published). We shall examine the details and implications of this suggestion.

Abundances of Lithium, Beryllium, and Lead in the Solar Atmosphere.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Abundances of Lithium, Beryllium, and Lead in the Solar Atmosphere. Mutschlecner, J. P. Abstract A redetermination has been made of the abundances of the elements lithium, beryllium, and lead in the solar atmosphere. The observational material consisted of numerous spectral scans obtained with the vacuum spectrograph of the McMath-Hulbert Observatory. Exact curves of growth were computed for each line using digital-computer programs. Features of the theoretical calculations include (1) the use of a newly derived semiempirical solar model atmosphere, (2) the inclusion of an empirically determined component of the continuous absorption coefficient in those regions where it was required, (3) an analysis of the influence of various uncertainties on the curve of growth and hence on the derived abundances. The resulting abundances on the silicon scale (i.e., number of atoms per million Si atoms) are: N(Li)=1.1, N(Be)=6.9, N(Pb)=1.4. An analysis of the source of errors shows that basic uncertainties in the solar model probably produce the largest abundance uncertainties. The upper limit to the combined error due to all sources is about 100% for lithium and lead and about 30% for beryllium. The beryllium and lead values are in good accord with meteoritic determinations while the solar lithium value is as little as 2% of meteoritic abundances. It is impossible at present to derive any conclusions as the depth of the solar convective zone from the lithium and beryllium abundances because of poor knowledge of the past history of the convective zone. The lead abundance is in reasonable agreement with a semi-theoretical prediction of the abundance by Clayton et al. EAnn. Phys. (N.Y.) 12, 331, 1961J based upon a detailed analysis of the s-process for nuclear synthesis. This work was done under auspices of University of Michigan Astronomy Department, Ann Arbor, Michigan, in partial fulfillment of Ph.D. ~equirements. Publication: The Astronomical Journal Pub Date: June 1963 DOI: 10.1086/109148 Bibcode: 1963AJ.....68S.287M full text sources ADS |