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Revista mexicana de astronomía y astrofísica
versión impresa ISSN 0185-1101
Rev. mex. astron. astrofis vol.43 no.1 Ciudad de México ene. 2007
LONG GAMMARAY BURST PROMPT EMISSION PROPERTIES AS A COSMOLOGICAL TOOL
C. Firmani,3 V. AvilaReese,2 G. Ghisellini,1 and G. Ghirlanda1
1 INAFOsservatorio Astronomico di Brera, via E. Bianchi 46, I23807 Merate, Italy (giancarlo.ghirlanda@brera.inaf.it, gabriele.ghisellini@brera.inaf.it)
2 Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70264, 04510 México, D. F., Mexico (avila@astroscu.unam.mx)
3 INAFOsservatorio Astronomico di Brera, via E. Bianchi 46, I23807 Merate, Italy and Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70264, 04510 México, D. F., Mexico (firmani@merate.mi.astro.it)
Received 2007 January 11
Accepted 2007 February 1
RESUMEN
Se usa una estrecha correlación entre 3 propiedades de la emisión 7 de los Estallidos de Rayos Gamma (ERGs) con corrimiento al rojo z conocido (Firmani et al. 2006a) para constreñir parámetros cosmológicos (PCs) en el diagrama de Hubble (DH) con una muestra de 19 ERGs en el amplio rango de z = 0.17 4.5. El problema de la circularidad se resuelve con un enfoque bayesiano. Encontramos que la cosmología de concordancia ACDM es consistente con los datos de los ERGs a nivel de varias pruebas. Si suponemos el modelo Λ, entonces = y el caso plano está dentro del la. Suponiendo planitud, obtenemos , y fijando Ωm= 0.28 obtenemos la ecuación de estado de la energía oscura , estando el caso ACDM (w = 1) dentro del la. Dado el bajo número de ERGs útiles no se puede aún constreñir bien la evolución de w = w(z), pero encontramos que el caso w(z) = 1 (ACDM) es consistente al 68.3% CL con los ERGs. Demostramos cómo un amplio rango de z's en la muestra usada (como es el caso de los ERGs) mejora la determinación de los PCs en el DH.
ABSTRACT
Recently, a tight correlation among three quantities that characterize the prompt emission of long GammaRay Bursts (GRBs) with known redshift z, was discovered (Firmani et al. 2006a). We use this correlation to construct the Hubble diagram (HD) with a sample of 19 GRBs in the broad range of z = 0.17 4.5, and carry out a full statistical analysis to constrain cosmological parameters (CPs). To optimally solve the problem of circularity, a Bayesian approach is applied. The main result is that the concordance ACDM cosmology is fully consistent with the GRB data at the level of several tests. If we assume the Λ cosmology, then we find and the flatgeometry case is within la. Assuming flatness, we find , and fixing Ωm =0.28, we obtain a dark energy equation of state parameter , i.e. the ACDM model (w = 1) is within 1σ. Given the low number of usable GRBs we cannot yet constrain well the possible evolution of w = w(z). However, the case w(z) = 1 (ACDM) is consistent at the 68.3% CL with GRBs. It is shown also how a broad range of z's in the used sample improves the determination of CPs from the HD, which is the case of GRBs as distance indicators.
Key Words: COSMOLOGICAL PARAMETERS COSMOLOGY: OBSERVATIONS DISTANCE SCALE GAMMA RAYS: BURSTS
DESCARGAR ARTÍCULO EN FORMATO PDF
ACKNOWLEDGEMENTS
We thank Giuseppe Malaspina for technical support, and Jana Benda for grammar corrections. We are grateful to the anonymous referee for a through and constructive report that helped to improve the content of the paper. VAR. gratefully acknowledges the hospitality extended by Osservatorio Astronomico di Brera. This work was supported by PAPIITUNAM grant IN1077063 and by the Italian INAF MIUR (Cofin grant 2003020775002).
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