Dust extinction properties of a sample of bright X-rays afterglows

Stratta, G. and Perna, R. and Lazzati, D. and Fiore, F. and Antonelli, A. and Conciatore, M. L. (2005) Dust extinction properties of a sample of bright X-rays afterglows. Il nuovo cimento C, 28 (4\5). pp. 693-696. ISSN 1826-9885

ncc9074.pdf - Published Version

Download (145kB) | Preview
Official URL: https://www.sif.it/riviste/sif/ncc/econtents/2005/...


Weha vestudie d a sampleof four bright X-rays afterglows of Gammaray Bursts (GRBs) for which the optical spectral energy distributions (SEDs), not corrected for extra-galactic dust extinction, have spectral index consistent with the X-rays spectral index, but with fluxes significantly below the X-rays extrapolation assuming a simple power law spectral model. A simple power law model is suggested by the spectral and temporal indices of these afterglows as already noted in previous works, although a spectral break between the X-rays and the optical band cannot be excluded but in one case. Previous works invoked a non standard extinction law to recover the observed spectral “mismatch”; alternatively, the same electron population may have produced the observed NIR-optical emission via synchrotron radiation and the X-rays via Inverse Compton scattering. We have investigated on the non-standard extinction hypothesis, since high redshift environments can be in principle very different from standard (local) interstellar media and GRB circumburst environment may well be modified by the burst itself. Although the uncertainty on the underlying spectral model prevented us to reach firm conclusions, we found that an extinction curve weakly dependent on the wavelenght makes the optical SED consistent with the X-rays flux extrapolation assuming a simple power law model and provides at the same time rest frame visual extinction values nicely in agreement with the equivalent hydrogen column densities measured from X-rays analysis. An extinction law weakly dependent on the wavelenght can be provided by dust grains destruction dueto thein tenseX-ra ys and UV fluxes from theburst itself or by small dust grains coagulation into larger ones. The large sample of optical–to–X-rays spectrally monitored afterglows provided by Swift will address our findings.

Item Type: Article
Additional Information: Paper presented at the “4th Workshop on Gamma-Ray Burst in the Afterglow Era”, Rome, October 18-22, 2004.
Uncontrolled Keywords: γ-ray sources; γ-ray bursts ; Interstellar dust grains
Subjects: 500 Scienze naturali e Matematica > 520 Astronomia e scienze connesse
Depositing User: Marina Spanti
Date Deposited: 17 Mar 2020 13:37
Last Modified: 17 Mar 2020 13:37
URI: http://eprints.bice.rm.cnr.it/id/eprint/15854

Actions (login required)

View Item View Item