The optical and X-ray light curves of long gamma-ray bursts (GRBs) often show a complex evolution and in most cases do not track each other. This behaviour cannot be easily explained by the simplest standard afterglow models. A possible interpretation is to consider the observed optical and X-ray light curves as the sum of two separate components. This scenario requires the presence of a spectral break between these bands. One of the aims of this work is to test whether such a break is present within the observed Swift X-Ray Telescope energy range. We analyse the X-ray afterglow spectra of a sample of 33 long GRBs with known redshift, good optical photometry and published estimate of the host galaxy dust absorption A_V(host). We find that indeed in seven bright events a broken power law provides a fit to the data that is better than a single power-law model. For eight events, instead, the X-ray spectrum is better fitted by a single power law. We discuss the role of these breaks in connection to the relation between the host hydrogen column density NH(host) and AhostV and check the consistency of the X-ray spectral breaks with the optical bands photometry. We analyse the optical to X-ray spectral energy distributions at different times and find again consistency with two components interpretation.
Nardini, M., Ghisellini, G., Ghirlanda, G., & Celotti, A. (2010). Testing a new view of gamma-ray burst afterglows. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 403(3), 1131-1142.
|Citazione:||Nardini, M., Ghisellini, G., Ghirlanda, G., & Celotti, A. (2010). Testing a new view of gamma-ray burst afterglows. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 403(3), 1131-1142.|
|Tipo:||Articolo in rivista - Articolo scientifico|
|Carattere della pubblicazione:||Scientifica|
|Titolo:||Testing a new view of gamma-ray burst afterglows|
|Autori:||Nardini, M; Ghisellini, G; Ghirlanda, G; Celotti, A|
|Data di pubblicazione:||16-mar-2010|
|Rivista:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1111/j.1365-2966.2009.16160.x|
|Appare nelle tipologie:||01 - Articolo su rivista|