116491269
Spherical symmetry in Rainich's theory
117096979
EQUATIONS OF MOTION IN EINSTEIN'S UNIFIED FIELD THEORY.
124396676
A COMMENT ON A CRITICISM OF THE NONSYMMETRIC UNIFIED FIELD THEORY
120241964
Is Rainich’s theory tenable?
122325575
An exact solution of the Einstein-Dirac equations
An exact solution to the Einstein-Dirac equations is obtained for a space-time with metric of the anisotropic cosmological type, the gravitational field having as its source a (massive) Dirac electron field.
119929847
The nonsymmetric unified field theory
This paper reviews the recent progress in the nonsymmetric unified field theory of Einstein and Straus and its current status as a theory of macrophysics of gravitation and electromagnetism.
22591121
First detection of ND in the solar-mass protostar IRAS16293-2422
Context. In the past decade, much progress has been made in characterising the processes leading to the enhanced deuterium fractionation observed in the ISM and in particular in the cold, dense parts of star forming regions such as protostellar envelopes. Very high molecular D/H ratios have been found for saturated molecules and ions. However, little is known about the deuterium fractionation in radicals, even though simple radicals often represent an intermediate stage in the formation of more complex, saturated molecules. The imidogen radical NH is such an intermediate species for the ammonia synthesis in the gas phase. Many of these light molecules however have their fundamental transitions in the submillimetre domain and their detection is hampered by the opacity of the atmosphere at these wavelengths. Herschel/HIFI represents a unique opportunity to study the deuteration and formation mechanisms of species not observable from the ground. Aims: We searched here for the deuterated radical ND in order to determine the deuterium fractionation of imidogen and constrain the deuteration mechanism of this species. Methods: We observed the solar-mass Class 0 protostar IRAS16293-2422 with the heterodyne instrument HIFI in Bands 1a (480-560 GHz), 3b (858-961 GHz), and 4a (949-1061 GHz) as part of the Herschel key programme CHESS (Chemical HErschel Survey of Star forming regions). Results: The deuterated form of the imidogen radical ND was detected and securely identified with 2 hyperfine component groups of its fundamental transition (N = 0-1) at 522.1 and 546.2 GHz, in absorption against the continuum background emitted from the nascent protostar. The 3 groups of hyperfine components of its hydrogenated counterpart NH were also detected in absorption. The absorption arises from the cold envelope, where many deuterated species have been shown to be abundant. The estimated column densities are ~2 × 1014 cm-2 for NH and ~ 1.3 × 1014 cm-2 for ND. We derive a very high deuterium fractionation with an [ND]/[NH] ratio of between 30 and 100%. Conclusions: The deuterium fractionation of imidogen is of the same order of magnitude as that in other molecules, which suggests that an efficient deuterium fractionation mechanism is at play. We discuss two possible formation pathways for ND, by means of either the reaction of N+ with HD, or deuteron/proton exchange with NH. Herschel is an ESA space observatory with science instruments provided by European-led principal Investigator consortia and with important participation from NASA.
54780575
Stellar evolution in real time: Period variations in galactic RR Lyr stars
The times of maximum brightness collected in the GEOS RR Lyr database allowed us to trace the period variations of a sample of 123 galactic RRab variables. These data span a time baseline exceeding 100 years. Clear evidence of period increases or decreases at constant rates has been found, suggesting evolutionary effects. The observed rates are slightly larger than those predicted by theoretical models; moreover, there is an unexpected large percentage of RRab stars showing a period decrease. The new possibilities offered by the use of robotic telecopes (TAROTs, REM) and of data from satellite (CoRoT) are expected to speed up the project to measure stellar evolution in real time. It is noteworthy that the outlines of this project have been sketched during several GEOS meetings, where the different knowledge of amateur and professional astronomers found a very profitable synthesis.
85444481
Detection of interstellar oxidaniumyl : Abundant H2O+ towards the star-forming regions DR21, Sgr B2, and NGC6334
Aims: We identify a prominent absorption feature at 1115 GHz, detected in first HIFI spectra towards high-mass star-forming regions, and interpret its astrophysical origin. Methods: The characteristic hyperfine pattern of the H2O+ ground-state rotational transition, and the lack of other known low-energy transitions in this frequency range, identifies the feature as H2O+ absorption against the dust continuum background and allows us to derive the velocity profile of the absorbing gas. By comparing this velocity profile with velocity profiles of other tracers in the DR21 star-forming region, we constrain the frequency of the transition and the conditions for its formation. Results: In DR21, the velocity distribution of H2O+ matches that of the [C ii] line at 158 μm and of OH cm-wave absorption, both stemming from the hot and dense clump surfaces facing the H ii-region and dynamically affected by the blister outflow. Diffuse foreground gas dominates the absorption towards Sgr B2. The integrated intensity of the absorption line allows us to derive lower limits to the H2O+ column density of 7.2 × 1012 cm-2 in NGC 6334, 2.3 × 1013 cm-2 in DR21, and 1.1 × 1015 cm-2 in Sgr B2. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
17272445
The CFHTLS real time analysis system: "optically selected GRB afterglows" Overview and performance
Aims. We describe a deep and wide search for optical GRB afterglows in images taken with MegaCAM at the Canada France Hawaii Telescope, within the framework of the CFHT Legacy Survey. Methods. This search is performed in near real-time thanks to a Real Time Analysis System (RTAS) called ”Optically Selected GRB Afterglows”, which has been installed on a dedicated computer in Hawaii. This pipeline automatically and quickly analyzes Megacam images to construct catalogs of astronomical objects, and compares catalogs made from images taken at different epochs to produce a list of astrometrically and photometrically variable objects. These objects are then displayed on a web page to be characterized by a member of the collaboration. Results. In this paper, we comprehensively describe the RTAS process from image acquisition to the final characterization of vari able sources. We present statistical results based on one full year of oper ation, showing the quality of the images and the performance of the RTAS. The limiting magnitude of our search is r’ =22.5 on average and the observed area amounts to 1178 square degrees. We have detected about 13.10 6 astronomical sources of which about 0.01% are found to vary by more than one tenth of a magnitude. We discuss the performance of our instrumental setup with a sample of simulated afterglows. This sample allows us to compare the effi ciency of our search with previous works, to propose an optimal observational strategy, and to discuss general considerations on the searches for GRB optical afterglows. We postpone to a forthcoming paper the discussion of the characterizati on of variable objects we have found, and a more detailled analysis of the nature of those resembling GRB afterglows. Conclusions. The RTAS has been continuously operating since November 2004. Each month 15-30 square degrees are observed many times over a period of 2-3 nights. The real-time analysis of the data has revealed no convincing afterglow candidate so far.
18597318
Stellar evolution through the ages: period variations in galactic RRab stars as derived from the GEOS database and TAROT telescopes
Context. The theory of stellar evolution can be more closely tested if we have the opportunity to measure new quantities. Nowadays, observations of galactic RR Lyr stars are available on a time baseline exceeding 100 years. Therefore, we can exploit the possibility of investigating period changes, continuing the pioneering work started by V. P. Tsesevich in 1969. Aims. We collected the available times of maximum brightness of the galactic RR Lyr stars in the GEOS RR Lyr database. Moreover, we also started new observational projects, including surveys with automated telescopes, to characterise the O‐C diagrams better. Methods. The database we built has proved to be a very powerful tool for tracing the period variations through the ages. We analyzed 123 stars showing a clear O‐C pattern (constant, parabolic or erratic) by means of different least‐squares methods. Results. Clear evidence of period increases or decreases at constant rates has been found, suggesting evolutionary effects. The median values are �=+0.14 d Myr −1 for the 27 stars showing a period increase and �=‐0.20 d Myr −1 for the 21 stars showing a period decrease. The large number of RR Lyr stars showing a period decrease (i.e., blueward evolution) is a new and intriguing result. There is an excess � � � �