Related papers: Cosmic Deuterium Or A Hydrogen Interloper ?
Cassini-Huygens data are used to re-examine the potential sources of the D/H enhancement over solar, measured in methane, in Titan's atmosphere. Assuming that the system is closed with respect to carbon, the use of constraints from the…
Big-bang nucleosynthesis (BBN) theory, together with the precise WMAP cosmic baryon density, makes tight predictions for the abundances of the lightest elements. Deuterium and 4He measurements agree well with expectations, but 7Li…
The origin of Earth oceans is controversial. Earth could have acquired its water either from hydrated silicates (wet Earth scenario) or from comets (dry Earth scenario). [HDO]/[H2O] ratios are used to discriminate between the scenarios.…
We examine the relationship between galaxies and the intergalactic medium at z < 1 using a group of three closely spaced background QSOs with z_em ~1 observed with the Hubble Space Telescope. Using a new grouping algorithm, we identify…
We study the X-ray absorption of a complete sample of 99 bright Swift gamma-ray bursts. Over the last few years, a strong correlation between the intrinsic X-ray absorbing column density (N_H(z)) and the redshift was found. This absorption…
Aims. We explore different scenarios to explain the chemical difference found in the remarkable giant-giant binary system HD 138202 + CD-30 12303. For the first time, we suggest how to distinguish these scenarios by taking advantage of the…
We investigate deuterium atoms adsorbed on the surface of liquid helium in equilibrium with a vapor of atoms of the same species. These atoms are studied by a sensitive optical method based on spectroscopy at a wavelength of 122 nm,…
After a brief review of the cosmological lithium problem, we report a few recent attempts to find theoretical solutions by our group at Texas A&M University (Commerce & College Station). We will discuss our studies on the theoretical…
New results, namely the independent determination of the deuterium abundance in several quasar absorption systems, and the complementary determination of the cosmological baryon density by observations of anisotropies in the cosmic…
The recent discovery of examples of intermediate-mass helium stars have offered new insights into interacting binaries. These observations will allow significant improvements in our understanding of helium stars. However, in the creation of…
The cosmological abundance of nucleons determined from considerations of Big Bang nucleosynthesis allegedly provides compelling evidence for non-nucleonic dark matter. Recent developments in measurements of primordial light element…
Abundance histories for QSO absorption line systems as a function of redshift are presented for all metals lighter than gallium. Coupling various conventional cosmological models with a simple, first--order model for the chemical evolution…
Recent astronomical observations of high redshift quasars, dark matter-dominated galaxies, mergers of neutron stars, glitch phenomena in pulsars, cosmic microwave background and experimental data from hadronic colliders do not rule out, but…
Super-high energy corpuscular and gamma rays as well as cosmic high--power density sources are hard to explain in a galaxy model framework. Attempts to include some of those phenomena in the Standard Cosmological Model also encounter…
It is suggested that essentially all of the UHECRs we detect, including those at the highest energy, originate in our Galaxy. It is shown that even if the density of sources decreases with Galactic radius, then the anisotropy and…
The importance of HST for the study of quasar absorption lines and of the nature of the intergalactic medium is illustrated by reviewing selected results from past HST observations. Topics reviewed include the study of Ly-alpha absorbers at…
Apart from the suspected violation of the CPT invariance, we might expect if the measurements of antihydrogen atoms provide testing Weak Equivalence Principle (WEP) in the gravitational phenomena. We start with how its violation can be…
We present the first results from a survey of the relative spatial distributions of galaxies, intergalactic neutral hydrogen, and intergalactic metals at high redshift. We obtained high-resolution spectra of 8 bright QSOs at 3.1<z<4.1 and…
Some form of missing energy may account for the difference between the observed cosmic matter density and the critical density. Two leading candidates are a cosmological constant and quintessence (a time-varying, inhomogenous component with…
The primordial abundance of deuterium produced during Big Bang Nucleosynthesis (BBN) depends sensitively on the universal ratio of baryons to photons, an important cosmological parameter probed independently by the Cosmic Microwave…