An iron absorption model of gamma-ray burst spectra

Liang, Edison; Kargatis, Vincent E.

doi:10.1086/187524

Cited by 8 publications

(7 citation statements)

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“…They therefore concluded that this scenario may be ruled out. Using our detailed photoionization calculations, we have re-investigated this idea under more realistic assumptions, and basically confirm the previous results of Liang & Kargatis (1994).…”

Section: Introductionsupporting

confidence: 83%

“…We investigated whether photoelectric absorption of the intrinsic γ-ray burst spectrum in the vicinity of the GRB could be responsible for the hard low-energy spectra of GRBs and their temporal evolution. This process has first been studied in the context of the low-energy spectra of γ-ray bursts by Liang & Kargatis (1994). Considering the photoelectric absorption of an unbroken power-law spectrum by pure neutral iron along the line of sight to a GRB, they found that an absorption depth at the iron K edge of several hundred is necessary to account for the steep γ-ray burst spectra if the intrinsic spectrum is an unbroken power-law with the spectral index observed above the break.…”

Section: Introductionmentioning

confidence: 99%

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

Böttcher

Dermer

Liang

1999

Astron. Astrophys. Suppl. Ser.

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Abstract. If γ-ray bursts (GRBs) are associated with dense star-forming regions, photoelectric absorption by the circumburster material (CBM) will occur. As the burst evolves, the surrounding material is photoionized, leading to fluorescence line emission and reduced photoelectric absorption opacity. We have numerically simulated this problem, accounting for all relevant microscopic processes. We find that if GRBs are hosted in a quasi-isotropic surrounding medium, photoionization of the CBM leads to a constant but weak level of delayed fluorescence line emission on timescales of weeks to months after the GRB. A temporally evolving Fe K edge absorption feature can serve as diagnostic tool for redshift measurements.

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Section: Introductionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

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

Böttcher

Dermer

Liang

1999

Astron. Astrophys. Suppl. Ser.

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“…In the case of the gamma-ray burst the photon flux is so intense that all of the atoms are stripped of their electrons before the burst photons completely pass a given point in space. Liang & Kargatis (1994) noted this effect. The other point is that the cross section of the atomic electrons decreases rapidly with increasing energy resulting in the removal of the electrons from the outside of the atom toward the inside which reduces the intensity of fluorescent K photons by about a factor of twenty.…”

Section: Observational Strategymentioning

confidence: 84%

Gamma-ray burst afterglow observations using AXAF and ACIS

Garmire

1999

Astron. Astrophys. Suppl. Ser.

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Abstract. With the successful launch of AXAF next summer, it will be possible to observe the X-ray afterglow from gamma-ray bursts with much improved positional accuracy (∼ 1 arcsec) and sensitivity (2 − 10 keV, 1.5 10 −14 ergs/cm 2 /s in 10 ksec). A typical burst afterglow should be observable within about 10 hours after the position has been determined by BeppoSAX or any other satellite capable of determining the position to within about 5 arcmin and provide about 1000 counts in a 10 ksec integration using the ACIS on AXAF. To constrain the decrease of intensity with time, using existing data from BeppoSAX and ASCA, the burst should produce a measurable flux for up to about 4 months after the gamma-ray event for an observing time of about 40 ksec, if a simple extrapolation of the observed fall-off with time is assumed. Depending upon a number of assumptions, there is a slight possibility of observing iron lines from the gas immediately surrounding the gamma-ray burst source using a long exposure (> 100 ksec).

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“…A separate problem with the synchrotron shock model is that it violates the observed spectral evolution seen in many bursts (Crider et al 1997, Preece et al 1998. A terrace can in principle be produced also by the Compton attenuation of a power law spectrum by cold intervening material (Brainerd et al 1998, Brainerd 1994, Liang & Kargatis 1994. However, the extremely high column density (N H > 10 25 cm −2 ) required, even for sub-solar abundances of metals, would have completely absorbed the < 10 keV X-rays, contrary to the BeppoSAX results.…”

Section: Data Analysis and Interpretationmentioning

confidence: 89%

GRB 990123: The Case for Saturated Comptonization

Liang¹,

Crider²,

Boettcher³

et al. 1999

The Astrophysical Journal

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We find that the optical magnitudes of GRB990123 observed by ROTSE correlates with the magnitudes extrapolated from the simultaneous BATSE spectra, strongly suggesting that the optical, X-ray and gamma-ray photons originate from a single source. We then show that the broadband optical-gamma-ray spectra can be naturally fit by the saturated Compton model. We also derive the parameters of the Compton emitting shell from first principles.

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An iron absorption model of gamma-ray burst spectra

Cited by 8 publications

References 0 publications

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

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

Gamma-ray burst afterglow observations using AXAF and ACIS

GRB 990123: The Case for Saturated Comptonization

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