Dust Extinction of Gamma-Ray Burst Host Galaxies: Identification of Two Classes?

Chen, Shi-lun; Li, Aigen; Wei, Da-Ming

doi:10.1086/507129

Cited by 40 publications

(45 citation statements)

References 41 publications

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“…Comparing this with the N H derived from the X-ray spectrum, we find a deficit of optical extinction, as already found in most GRBs (Stratta et al 2004;Kann et al 2006;Galama & Wijers 2001). In principle this could be explained in a number of ways (see, e.g., the case of GRB 051111, Guidorzi et al 2007): (1) an extinction profile different from those typical of MW, SMC, LMC (e.g., Stratta et al 2004;Savaglio & Fall 2004); (2) a population of dust grains skewed toward big sizes, possibly as a result of dust destruction due to the GRB itself (e.g., Maiolino et al 2001;Chen et al 2006); (3) a significant presence of molecular gas (1999); (4) overabundance of some alpha metals responsible for absorption in X-rays (e.g., GRB 050401; Watson et al 2006).…”

Section: Resultsmentioning

confidence: 99%

The Remarkable Afterglow of GRB 061007: Implications for Optical Flashes and GRB Fireballs

Mundell

Melandri

Guidorzi

et al. 2007

ApJ

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We present a multiwavelength analysis of Swift GRB 061007. The 2 m robotic Faulkes Telescope South began observing 137 s after the onset of the -ray emission, when the optical counterpart was already decaying from R $ 10:3 mag, and continued observing for the next 5.5 hr. These observations begin during the final -ray flare and continue through and beyond a long, soft tail of -ray emission whose flux shows an underlying simple power-law decay identical to that seen at optical and X-ray wavelengths, with temporal slope $ 1:7 (F / t À ). This remarkably simple decay in all of these bands is rare for Swift bursts, which often show much more complex light curves. We suggest the afterglow emission begins as early as 30Y100 s and is contemporaneous with the ongoing variable prompt emission from the central engine, but originates from a physically distinct region dominated by the forward shock. The observed multiwavelength evolution of GRB 061007 is explained by an expanding fireball whose optical, X-ray, and late-time -ray emission is dominated by emission from a forward shock with typical synchrotron frequency, m , that is already below the optical band as early as t ¼ 137 s and a cooling frequency, c , above the X-ray band to at least t ¼ 10 5 s. In contrast, the typical frequency of the reverse shock lies in the radio band at early time. We suggest that the unexpected lack of bright optical flashes from the majority of Swift GRBs may be explained with a low m originating from small microphysics parameters, e and B . Finally, the optical light curves imply a minimum jet opening angle ¼ 4:7, and no X-ray jet break before t $ 10 6 s makes GRB 061007 a secure outlier to spectral energy correlations.

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Section: Resultsmentioning

confidence: 99%

The Remarkable Afterglow of GRB 061007: Implications for Optical Flashes and GRB Fireballs

Mundell

Melandri

Guidorzi

et al. 2007

ApJ

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“…The lack of reddening in the host galaxy spectrum may be explained by a localized dusty environment in the vicinity of the XRF, as suggested for GRB 000210, another "dark" burst with similar characteristics (Gorosabel et al 2003). Alternatively, the lack of reddening may be due to a weak wavelength dependence of the dust extinction law, as inferred for some GRBs and for other extragalactic objects such as AGNs (Maiolino et al 2000;Stratta et al 2004b;Chen et al 2006). In the latter case, a high equivalent hydrogen column density is expected from the X-ray data analysis, while we found a value consistent with the Galactic absorption.…”

Section: A "Dark" X-ray Flashmentioning

confidence: 86%

X-ray flashes or soft gamma-ray bursts?

Stratta¹,

Basa

Butler

et al. 2006

A&A

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Context. The origin of X-ray Flashes (XRFs) is still a mystery and several models have been proposed. To disentangle among these models, an important observational tool is the measure of the XRF distance scale, so far available only for a few of them. Aims. In this work, we present a multi-wavelength study of XRF 040912, aimed at measuring its distance scale and the intrinsic burst properties. Methods. We performed a detailed spectral and temporal analysis of both the prompt and the afterglow emission and we estimated the distance scale of the likely host galaxy. We then used the currently available sample of XRFs with known distance to discuss the connection between XRFs and classical Gamma-ray Bursts (GRBs). Results. We found that the prompt emission properties unambiguously identify this burst as an XRF, with an observed peak energy of E p = 17 ± 13 keV and a burst fluence ratio S 2−30 keV /S 30−400 keV > 1. A non-fading optical source with R ∼ 24 mag and with an apparently extended morphology is spatially consistent with the X-ray afterglow, likely the host galaxy. XRF 040912 is a very dark burst since no afterglow optical counterpart is detected down to R > 25 mag (3σ limiting magnitude) at 13.6 h after the burst. The host galaxy spectrum detected from 3800 Å to 10 000 Å, shows a single emission line at 9552 Å. The lack of any other strong emission lines blue-ward of the detected one and the absence of the Lyα cut-off down to 3800 Å are consistent with the hypothesis of the [OII] line at redshift z = 1.563 ± 0.001. The intrinsic spectral properties rank this XRF among the soft GRBs in the E peak −E iso diagram. Similar results were obtained for most XRFs at known redshift. Only XRF 060218 and XRF 020903 represent a good example of instrinsic XRF (i-XRF) and are possibly associated with a different progenitor population. This scenario may call for a new definition of XRFs.

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“…In Chen et al (2006) and Li et al (2008b) the optical intrinsic spectral index, β opt , was inferred indirectly by using the closure relations defined by synchrotron emission theory (Zhang & Mészáros 2004). In Chen et al (2006), β opt was calculated from the optical temporal decay index, α opt . Li et al (2008b), on the other hand, used a sample of GRBs with consistent X-ray and optical afterglow temporal indices, α opt and α x , and assumed the optical spectral index, β opt , to be the same as the measured X-ray spectral index, β x .…”

Section: Discussionmentioning

confidence: 99%

The dust extinction curves of gamma-ray burst host galaxies

Schady¹,

Dwelly²,

Page³

et al. 2011

A&A

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The composition and amount of interstellar dust within gamma-ray burst (GRB) host galaxies is of key importance when addressing selection effects in the GRB redshift distribution, and when studying the properties of their host galaxies. As well as the implications for GRB research, probing the dust within the high-z hosts of GRBs also contributes to our understanding of the conditions of the interstellar medium and star-formation in the distant Universe. Nevertheless, the physical properties of dust within GRB host galaxies continues to be a highly contended issue. In this paper we explore the mean extinction properties of dust within the host galaxies of a sample of 17 GRBs with total host galaxy visual extinction A V < 1 ( A V = 0.4), covering a redshift range z = 0.7−3.1. We find the average host extinction curve to have an ultraviolet slope comparable to that of the LMC, but with little evidence of a 2175 Å dust extinction feature as observed along Milky Way and LMC sightlines. We cannot at present rule out the presence of a 2175 Å feature, and both the standard SMC and LMC extinction curves also provide good fits to our data. However, we can reject an extinction curve that has a UV slope as flat as the mean Milky Way extinction curve, whilst also having a 2175 Å feature as prominent as seen in the mean Milky Way extinction curve. This is in contrast to the clear detection of a 2175 Å bump and the flatter extinction curves of some more heavily extinguished GRBs (A V > 1), which may be indicative of there being a dependence between dust abundance and the wavelength dependence of dust extinction, as has been previously speculated.

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Dust Extinction of Gamma-Ray Burst Host Galaxies: Identification of Two Classes?

Cited by 40 publications

References 41 publications

The Remarkable Afterglow of GRB 061007: Implications for Optical Flashes and GRB Fireballs

The Remarkable Afterglow of GRB 061007: Implications for Optical Flashes and GRB Fireballs

X-ray flashes or soft gamma-ray bursts?

The dust extinction curves of gamma-ray burst host galaxies

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