7,209 research outputs found

    New measurements of Ωm\Omega_m from gamma-ray bursts

    Get PDF
    Context: Data from cosmic microwave background radiation (CMB), baryon acoustic oscillations (BAO), and supernovae Ia (SNe-Ia) support a constant dark energy equation of state with w0∼−1w_0 \sim -1. Measuring the evolution of ww along the redshift is one of the most demanding challenges for observational cosmology. Aims: We discuss the existence of a close relation for GRBs, named Combo-relation, based on characteristic parameters of GRB phenomenology such as the prompt intrinsic peak energy Ep,iE_{p,i}, the X-ray afterglow, the initial luminosity of the shallow phase L0L_0, the rest-frame duration τ\tau of the shallow phase, and the index of the late power-law decay αX\alpha_X. We use it to measure Ωm\Omega_m and the evolution of the dark energy equation of state. We also propose a new calibration method for the same relation, which reduces the dependence on SNe Ia systematics. Methods: We have selected a sample of GRBs with 1) a measured redshift zz; 2) a determined intrinsic prompt peak energy Ep,iE_{p,i}, and 3) a good coverage (0.3-10) keV afterglow light curves. The fitting technique of the rest.frame (0.3-10) keV luminosity light curves represents the core of the Combo-relation. We separate the early steep decay, considered a part of the prompt emission, from the X-ray afterglow additional component. Data with the largest positive residual, identified as flares, are automatically eliminated until the p-value of the fit becomes greater than 0.3. Results: We strongly minimize the dependency of the Combo-GRB calibration on SNe Ia. We also measure a small extra-Poissonian scatter of the Combo-relation, which allows us to infer from GRBs alone ΩM=0.29−0.15+0.23\Omega_M =0.29^{+0.23}_{-0.15} (1σ\sigma) for the Λ\LambdaCDM cosmological model, and ΩM=0.40−0.16+0.22\Omega_M =0.40^{+0.22}_{-0.16}, w0=−1.43−0.66+0.78w_0 = -1.43^{+0.78}_{-0.66} for the flat-Universe variable equation of state case.Comment: 10 pages, 9 figures, 3 tables. Accepted for publication in A&A. Truncated abstract tex

    Co-Rh modified natural zeolites as new catalytic materials to oxidize propane and naphthalene from emission sources

    Get PDF
    Natural zeolites as a raw material to prepare catalytic precursors for the oxidation reaction of linear and poly-aromatic hydrocarbons are reported in this work. The process consisted in the formation of mono- and bi-metallic species containing Co and Co-Rh on natural zeolite tuffs. The materials are analyzed by different physicochemical techniques and used as catalysts for propane and naphthalene oxidation in emissions sources. Comparatively, Rh-zeolites are the most active catalysts for propane conversion. In this case, the formation of mixed oxides seems to be conditioned by surface properties. It could also be suggested that the Rh incorporation on a non-active phase in bimetallic catalysts impacts the effectiveness of the system. In addition, the NO presence increases the activity of bimetallic materials. Rh-Co zeolite systems markedly influence the naphthalene combustion temperature. Whereas in the absence of a catalyst a conversion rate of 50% and 100% is reached at 430 C and 485 °C, respectively. It is interesting to observe that for RhCoCli-Mor and RhCoCli catalyst the 100% conversion is reached at 250 °C.Fil: Leguizamón Aparicio, María Silvia del Valle. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Canafoglia, Maria Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; ArgentinaFil: Ocsachoque, Marco Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Lick, Ileana Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Botto, Irma Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica ; Argentin
    • …
    corecore