Time-dependent photoionization and fluorescence line emission in gamma-ray
burst environments

Böttcher, M.; Dermer, C. D.; Liang, Edison

doi:10.1051/aas:1999345

Cited by 10 publications

(9 citation statements)

References 17 publications

(29 reference statements)

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“…Thus, we conclude that the burst has about the right number of photons to cause the complete photoionization of iron within the B time interval, with recombination providing no real counter-effect. A similar conclusion, with a more elaborate computation, has been reached, for generic parameters, by Böttcher et al (4).…”

supporting

confidence: 83%

Discovery of a Transient Absorption Edge in the X-ray Spectrum of GRB 990705

Amati¹,

Frontera

Vietri³

et al. 2000

Science

170

199

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We report the discovery of a transient equivalent hydrogen column density with an absorption edge at ∼3.8 kiloelectron volts in the spectrum of the prompt x-ray emission of gamma-ray burst (GRB) 990705. This feature can be satisfactorily modeled with a photoelectric absorption by a medium located at a redshift of ∼0.86 and with an iron abundance of ∼75 times the solar one. The transient behavior is attributed to the strong ionization produced in the circumburst medium by the GRB photons. The high iron abundance points to the existence of a burst environment enriched by a supernova along the line of sight. The supernova explosion is estimated to have occurred about 10 years before the burst. Our results agree with models in which GRBs originate from the collapse of very massive stars and are preceded by a supernova event.

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supporting

confidence: 83%

Discovery of a Transient Absorption Edge in the X-ray Spectrum of GRB 990705

Amati¹,

Frontera

Vietri³

et al. 2000

Science

170

199

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“…Thus, the size limit, together with the restriction that in the GRBs with line detections, there is no indication for excess X-ray absorption, leads to typical mass estimates of M Fe ∼ 0.1 -1 M ⊙ of iron, confined in R < ∼ 10 −3 pc, if the line emission were to originate in a dilute, quasi-isotropic environment. This is unlikely to be realized in any astrophysical setting, and may thus be ruled out (Ghisellini et al 1998, Böttcher et al 1999. We therefore find that inhomogeneous media with significant density enhancement outside our line of sight toward the GRB source are required (e.g., Lazzati et al 1999, Böttcher 2000.…”

Section: General Constraints From Emission Line Featuresmentioning

confidence: 73%

“…Time-dependent X-ray absorption features had been studied for generic, quasi-homogeneous environments by Böttcher et al (1999) and Ghisellini et al (1999), and for more general cases, including radial gradients, by and Lazzati & Perna (2002). For given values of the depth τ edge of an absorption edge and the time scale t edge within which it is disappearing, one can directly infer a characteristic radius (by setting t ion = t edge ).…”

Section: Model Implications Of the Transient Absorption Featurementioning

confidence: 99%

“…Atomic X-ray absorption features in GRB afterglows are rather common. However, in order to distinguish such features from foreground absorption and to associate them physically with the GRB, one needs to find evidence for variability of those absorption features on the GRB / early afterglow time scale (Perna & Loeb 1998, Böttcher et al 1999. Until now, only one such case has been observed: GRB 990705 (Amati et al 2000).…”

Section: The Transient Absorption Feature In Grb 990705mentioning

confidence: 99%

“…In principle, inferring constraints on parameters of the circumburster material from observed GRB properties is an easier task than inferring them from emission lines, because in the case of absorption features the continuum responsible for photoionization is identical to the observed GRB and afterglow continuum. Time-dependent X-ray absorption features had been studied for generic, quasi-homogeneous environments by Böttcher et al (1999) and Ghisellini et al (1999), and for more general cases, including radial gradients, by Lazzati et al (2001) and Lazzati & Perna (2002). For given values of the depth τ edge of an absorption edge and the time scale t edge within which it is disappearing, one can directly infer a characteristic radius (by setting t ion = t edge ).…”

Section: Model Implications Of the Transient Absorption Featurementioning

confidence: 99%

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X-ray lines and absorption edges in GRBS and their afterglows

Böttcher

2004

Advances in Space Research

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Absorption and Reprocessing of Gamma-ray burst radiation in the environment of cosmological GRBs can be used as a powerful probe of the elusive nature of their progenitors. In particular, transient X-ray emission line and absorption features in the prompt and early afterglows of GRBs are sensitive to details of the location and density structure of the reprocessing and/or absorbing material. To date, there have been only rather few detections of such features, and the significance is marginal in most individual cases. However, transient X-ray emission lines in GRB afterglows have now been found by four different X-ray satellites, which may justify a more detailed theoretical investigation of their origin. In this paper, I will first present a brief review of the status of observations of transient X-ray emission line and absorption features. I will then discuss general physics constraints which those results impose on isotropy, homogeneity, and location of the reprocessing material with respect to the GRB source, and review the various currently discussed, specific models of GRBs and their environments in which the required conditions could arise. SUMMARY OF OBSERVED X-RAY LINES AND ABSORPTION FEATURESThe precise localization of gamma-ray bursts (GRBs) by the BeppoSAX satellite, launched in 1996, has facilitated the subsequent discovery of X-ray and optical GRB afterglows, the measurement of redshifts of GRBs and the firm establishment of their cosmological distance scale (at least for long GRBs with durations t 90 > ∼ 2 s) beyond any reasonable doubt. The physics of the radio through X-ray continuum afterglow emission are now believed to be rather well understood in terms of the external synchrotron shock model (for a recent review see, e.g., Mészáros 2002 or Dermer 2002). However, in spite of these significant advances, the ultimate source of GRBs is still a matter of vital debate. This is mainly due to the fact that the continuum GRB afterglows are the "smoking gun" of the GRB explosion, revealing only very little information about the initial energy source.However, even without a direct observation of the central engines of GRBs, it might be possible to infer their nature indirectly if detailed probes of the structure and composition of their immediate vicinity can be found. A promising candidate for such a probe is high-quality, time resolved X-ray spectroscopy of GRB afterglows, which is now becoming available with the new generation of X-ray telescopes like Chandra and XMM-Newton, and the planned Swift mission, scheduled for launch in September 2003. Previous and currently operating X-ray telescopes have so far (status: November 2002) revealed marginal evidence for X-ray emission lines (mostly consistent with Fe Kα fluorescence lines) or radiative recombination edges in 5 GRBs, and one case of a transient X-ray absorption feature at an energy consistent with an iron K absorption edge.In the remainder of this section, I will give a brief review of the observed X-ray spectral features in GRBs, befor...

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Gamma-Ray Bursts: The Underlying Model

Waxman

2003

Supernovae and Gamma-Ray Bursters

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A pedagogical derivation is presented of the ``fireball'' model of gamma-ray bursts, according to which the observable effects are due to the dissipation of the kinetic energy of a relativistically expanding wind, a ``fireball.'' The main open questions are emphasized, and key afterglow observations, that provide support for this model, are briefly discussed. The relativistic outflow is, most likely, driven by the accretion of a fraction of a solar mass onto a newly born (few) solar mass black hole. The observed radiation is produced once the plasma has expanded to a scale much larger than that of the underlying ``engine,'' and is therefore largely independent of the details of the progenitor, whose gravitational collapse leads to fireball formation. Several progenitor scenarios, and the prospects for discrimination among them using future observations, are discussed. The production in gamma- ray burst fireballs of high energy protons and neutrinos, and the implications of burst neutrino detection by kilometer-scale telescopes under construction, are briefly discussed.Comment: In "Supernovae and Gamma Ray Bursters", ed. K. W. Weiler, Lecture Notes in Physics, Springer-Verlag (in press); 26 pages, 2 figure

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Time-dependent photoionization and fluorescence line emission in gamma-ray burst environments

Cited by 10 publications

References 17 publications

Discovery of a Transient Absorption Edge in the X-ray Spectrum of GRB 990705

Discovery of a Transient Absorption Edge in the X-ray Spectrum of GRB 990705

X-ray lines and absorption edges in GRBS and their afterglows

Gamma-Ray Bursts: The Underlying Model

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