arXiv subjects

E. Rodriguez

Publications and source records attributed to E. Rodriguez.

42 records · Page 3Linked to original sources

arXiv2002

Does the proton-to-electron mass ratio vary in the course of cosmological evolution?

The possible cosmological variation of the proton-to-electron mass ratio was estimated by measuring the H_2 wavelengths in the high-resolution spectrum of the quasar Q~0347-382. Our analysis yielded an estimate for the possible deviation of μvalue in the past, 10 Gyr ago: for the unweighted value $Δμ/ μ= (3.0\pm2.4)\times10^{-5}$; for the weighted value \[ Δμ/ μ= (5.02\pm1.82)\times10^{-5}\] Since the significance of the both results does not exceed 3$σ$, further observations are needed to increase the statistical significance. In any case, this result may be considered as the most stringent estimate on an upper limit of a possible variation of μ(95% C.L.): \[ |Δμ/ μ| < 8\times 10^{-5} \] This value serves as an effective tool for selection of models determining a relation between possible cosmological deviations of the fine-structure constant αand the elementary particle masses (m$_p$, m$_e$, etc.).

astro-ph↗

arXiv2002

Abundance analysis of targets for the COROT / MONS asteroseimology missions I. Semi-automatic abundance analysis of the gamma Dor star HD 49434

One of the goals of the ground-based support program for the COROT and MONS/Roemer satellite missions is to select and characterise suitable target stars for the part of the missions dedicated to asteroseismology. While the global atmospheric parameters may be determined with good accuracy from the Stromgren indices, careful abundance analysis must be made for the proposed main targets. This is a time consuming process considering the long list of primary and secondary targets. We have therefore developed new software called VWA for this task. The VWA automatically selects the least blended lines from the atomic line database VALD, and consequently adjusts the abundance in order to find the best match between the calculated and observed spectra. The variability of HD 49434 was discovered as part of COROT ground-based support observations. Here we present a detailed abundance analysis of HD 49434 using VWA. For most elements we find abundances somewhat below the Solar values, in particular we find [Fe/H] = -0.13(14). We also present the results from the study of the variability that is seen in spectroscopic and photometric time series observations. From the characteristics of the variation seen in photometry and in the line profiles we propose that HD 49434 is a variable star of the gamma Doradus type.

astro-ph↗

arXiv2002

The multiperiodicity of the $γ$ Doradus stars HD 224945 and HD 224638 as detected from a multisite campaign

We discuss new photometric data collected on the gamma Dor variables HD 224945 and HD 224638. Multiperiodicity was detected in both stars, thanks to the clear spectral window of a multisite campaign that involved five observatories. HD 224945 shows the shortest period among the gamma Dor stars, i.e., 0.3330 d. The pulsation behaviour is very different: HD 224945 displays a set of frequencies spread over an interval much wider than that of HD 224638. We clearly found evidence for amplitude variations in the excited modes by comparing data from different years. HD 224945 and HD 224638 are among the best examples of $γ$ Dor stars that show multimode pulsations, which make them very interesting from an asteroseismological point of view.

astro-ph↗

arXiv2002

Do the Fundamental Constants Vary in the Course of the Cosmological Evolution?

We estimate the cosmological variation of the proton-to-electron mass ratio μ=m_p/m_e by measuring the wavelengths of molecular hydrogen transitions in the early universe. The analysis is performed using high spectral resolution observations (FWHM ~ 7 km/s) of two damped Lyman-αsystems at z_{abs}=2.3377 and 3.0249 observed along the lines of sight to the quasars Q 1232+082 and Q 0347-382 respectively. The most conservative result of the analysis is a possible variation of μover the last ~ 10 Gyrs, with an amplitude Δμ/μ= (5.7+-3.8)x10^{-5}. The result is significant at the 1.5σlevel only and should be confirmed by further observations. This is the most stringent estimate of a possible cosmological variation of μobtained up to now.

astro-ph↗

arXiv1999

Measuring the interaction force between a high temperature superconductor and a permanent magnet

Repulsive and attractive forces are both possible between a superconducting sample and a permanent magnet, and they can give place to magnetic levitation or free-suspension phenomena, respectively. We show experiments to quantify this magnetic interaction which represents a promising field regarding to short-term technological applications of high temperature superconductors. The measuring technique employs an electronic balance and a rare-earth magnet that induces a magnetic moment in a melt-textured YBa2Cu3O7 superconductor immersed in liquid nitrogen. The simple design of the experiments allows a fast and easy implementation in the advanced physics laboratory with a minimum cost. Actual levitation and suspension demonstrations can be done simultaneously as a help to interpret magnetic force measurements.

cond-mat.supr-con↗

arXiv1996

The Gamma Doradus variables, a new class of pulsating stars. The case of HD 224945

A multisite campaign involving five observatories allowed us to solve the light curve of the Gamma Doradus star HD 224945. The multiperiodic content, the high frequency term at 3.00 c/d and the frequency spacing between the observed terms strongly support its pulsational nature. Considering the low frequency terms observed in Gamma Dor stars, it seems that g--mode pulsators can be found near the cold border of the instability strip.

astro-ph↗