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Extinction Curves from Gamma-ray Burst Afterglows

This study explores the extinction curves observed in gamma-ray burst (GRB) afterglows, providing insights into the amount and properties of dust inferred from deviations in the spectrum. The research is carried out at the Dark Cosmology Centre/Niels Bohr Institute in Copenhagen, involving multiple contributors. The observations are mainly conducted at the ESO Very Large Telescope using spectroscopy and imaging techniques. The results reveal various extinction characteristics in different GRBs, such as SMC-like reddening and the presence of 2175Å bump. The findings contribute to the understanding of star formation and the interpretation of the extragalactic background light (EBL) spectrum.

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Extinction Curves from Gamma-ray Burst Afterglows

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  1. Extinction Curves from Gamma-ray Burst Afterglows Johan Fynbo Dark Cosmology Centre/Niels Bohr Institute/Copenhagen Work done by many: Andersen, Elíasdóttir, Gorosabel, Hjorth, Jakobsson, Jaunsen, Jensen, Ledoux, Leloudas, Levan, Malesani, Milvang-Jensen, Starling, Tanvir, Vreeswijk, Wiersema, Watson, Zafar, Xu, and several more

  2. Gamma-ray bursts ARA&A reviews: van Paradijs, Kouveliotou & Wijers 2000, Mészáros 2002, Woosley & Bloom 2006

  3. Theoretical afterglow spectra N(e) (Sari, Piran & Narayan 1998) N(e) e-p cooling e Low-frequency synchtron Self-absorbed fast cooling  ~ B e2

  4. Extinction curves from GRB afterglows The approach is simple: The amount and properties of the dust is inferred from the deviations from a power-law spectrum. Reichart (1998), Jakobsson et al. (2003)

  5. How we observe • Mainly carried out at the ESO Very Large Telescope using one of the FORS1/2 instruments. • Long-slit, low-resolution spectroscopy or broad band imaging. • The instruments have “atmospheric dispersion correctors”. • The spectra are flux-calibrated using observations of spectro-photometric standard stars.

  6. GRB071031, z=2.69, no extinction

  7. GRB050401, z=2.89, VLT, substantial SMC-like reddening 2175Å bump Watson et al. 2006

  8. GRB050401, z=2.89, VLT, substantial SMC-like reddening Low dust-to-metals ratio, but significant depletion (?) 2175Å bump Watson et al. 2006

  9. z=2.45, VLT, 2175Å bump 2175Å bump Eliasdóttir et al. 2009, Kruehler et al. 2008

  10. GRB080605, z=1.65, VLT Xu et al. 2009

  11. z=3.04, VLT, 2175Å bump Prochaska et al. 2009

  12. z=1.50, strong reddening (in a blue host)

  13. z=0.84, reddening?

  14. Building a complete sample of Swift GRBs Gehrels et al. 2004, Schady et al. 2007, Evans et al. 2009 X-ray selected sample Jakobsson et al. 2006, A&A, 447, 897; Fynbo et al., in prep) March 2005 - September 2008: • 146 bursts • 106 optical afterglows detected • 71 redshifts from afterglow spec.

  15. QSO-DLAs and GRB absorbers

  16. Evidence for many more dusty sightlines

  17. Hauser & Dwek, ARA&A 2001

  18. “Thermal emission from dust dominates the EBL spectrum at wavelengths longward of 3.5μ and constitutes about 48% of the nominal EBL. However, values ranging from 20% to 80% are consistent with the measurement uncertainties (shaded area).” GRBs could in principle provide a star-formation weighted mean extinction curve and its evolution with redshift. This would be a central element to establish for the interpretation of the EBL spectrum. Hauser & Dwek, ARA&A 2001

  19. Distant red galaxies GRB hosts Damped Lyman-aAbsorbers Lyman-agalaxies Lyman-break galaxies Where are the bulk of the massive stars formed ? GRBs may give the answer SMGs

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