8533691
Constraining the rate of GRB visible afterglows with the CFHTLS very wide survey
We have analyzed 2231 images of the CFHTLS Very Wide survey to search visible orphan afterglows from GRBs. Our search covers 490 square degrees down to magnitude r′ = 22.5, and to date it provides the strongest constraints on the rate of GRB visible afterglows. We have found zero GRB optical afterglow and one remarkable event, which could be a micro‐lensing event. We measure the detection efficiency of our search with a MC simulation reproducing the characteristics of our observational strategy and the properties of on‐axis GRB afterglows. This simulation allows us to translate our observations into constraints on the rate of GRB visible afterglows, which is found to be less than 220 afterglows brighter than m = 22.5 in all sky at any time (or 10000 optical afterglows/year/all‐sky). Our observations are marginally consistent with the most optimistic models, which predict orphan afterglows to be about 10 times more frequent than GRBs at m = 22.5.
7878763
Limits on the early afterglow phase of gamma-ray burst sources from TAROT-1
The Telescope a Action Rapide pour les Objets Transitoires (TAROT-1) has as prime objective the observation of the prompt and delayed emission of cosmic gamma-ray bursts (GRBs). We have performed a search for optical emission from 6 GRBs detected by BATSE. The positioning error circle was fully covered within typically thirty minutes after the trigger. No detection of the early afterglow phase was made, and magnitude limits in the range of $ \\mathrm{m}_{\\mathrm{R}} = 13-15 $ were estimated using 20s exposures. These limits are compared to optical afterglow data obtained in later phases and the results are interpreted in terms of source distances. They correspond to a median redshift of z = 0.5. With HETE-2 and the planned instrument upgrade, TAROT-1 will be able to detect the early optical emission of GRBs up to a redshift of the order of 5.
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 � � � �
14536809
A multiwavelength study of Swift GRB 060111B constraining the origin of its prompt optical emission
In this work, we present the results obtained from a multi-wavelength campaign, as well as from the public Swift/BAT, XRT, and UVOT data of GRB 060111B for which a bright optical emission was measured with good temporal resolution during the prompt phase. We identified the host galaxy at R~25 mag; its featureless spectral continuum and brightness, as well as the non-detection of any associated supernova 16 days after the trigger and other independent redshift estimates, converge to z~1-2. From the analysis of the early afterglow SED, we find that non-negligible host galaxy dust extinction, in addition to the Galactic one, affects the observed flux in the optical regime. The extinction-corrected optical-to-gamma-ray spectral energy distribution during the prompt emission shows a flux density ratio $F_{\gamma}/F_{opt}$=0.01-0.0001 with spectral index $\beta_{\gamma,opt}> \beta_{\gamma}$, strongly suggesting a separate origin of the optical and gamma-ray components. This result is supported by the lack of correlated behavior in the prompt emission light curves observed in the two energy domains. The properties of the prompt optical emission observed during GRB 060111B favor interpretation of this optical light as radiation from the reverse shock in a thick shell limit and in the slow cooling regime. The expected peak flux is consistent with the observed one corrected for the host extinction, likely indicating that the starting time of the TAROT observations is very near to or coincident with the peak time. The estimated fireball initial Lorentz factor is >260-360 at z=1-2, similar to the Lorentz factors obtained from other GRBs. GRB 060111B is a rare, good test case of the reverse shock emission mechanism in both the X-ray and optical energy ranges.
117717977
Optically Selected GRB Afterglows, a Real Time Analysis System at the CFHT
We attempt to detect optical GRB afterglows on images taken by the Canada France Hawaii Telescope for the Very Wide survey, component of the Legacy Survey. To do so, a Real Time Analysis System called "Optically Selected GRB Afterglows" has been installed on a dedicated computer in Hawaii. This pipeline automatically and quickly analyzes Megacam images and extracts from them a list of variable objects which is displayed on a web page for validation by a member of the collaboration. The Very Wide survey covers 1200 square degrees down to i'=23.5. This paper briefly explain the RTAS process.
54637934
The puzzling temporally variable optical and X-ray afterglow of GRB 101024A
Aims. We present the optical observations of the afterglow of the Swift burst GRB 101024A and try to reconcile these observations with the X-ray afterglow data of GRB 101024A using current afterglow models Methods. We employ early optical observations, using the Zadko Telescope combined with X-ray data, to compare them with the reverse shock/forward shock model. Results. The early optical light curve reveals a very unusual steep decay index of α ∼ 5. This is followed by a flattening and possibly a plateau phase coincident with a similar feature in the X-ray. We discuss these observations in the framework of the standard reverse shock/forward shock model and energy injection. The plateau phase might also be the signature of the formation of a new magnetar.
118183813
A revised nonsymmetric unified field theory.
123739614
Static, cylindrically symmetric solution of the generalized field equations
The problem of finding cylindrically symmetric static solutions of the Generalized Field Theory is completely solved. The electromagnetic fields are shown to vanish faster with the distance from the axis of symmetry than the corresponding curvature of the associated space-time. On the other hand, when the latter becomes at flat Minkowski manifold, the symmetric field is zero but the theory predicts exactly the Maxwellian electric and magnetic fields
124396676
A COMMENT ON A CRITICISM OF THE NONSYMMETRIC UNIFIED FIELD THEORY
116472076
Equations of motion in a cylindrical field
The equations of motion of a test particle are derived from the field equations of Einstein's unified field theory in the case when there is a cylindrically symmetric source. An exact form of the equations of motion, corresponding to a particular solution of the field equations, is obtained. (auth)
118920862
Cosmological implications of the unified field theory.