Can the Bump Be Observed in the Early Afterglow of Gamma‐Ray Bursts with X‐Ray Line Emission Features?

Abstract

Extremely powerful emission lines are observed in the X-ray afterglow of several gamma-ray bursts (GRBs). The energy contained in the illuminatingcontinuum that is responsible for the line production exceeds 10 51 ergs, much higher than that of the collimated GRBs, constraining the models that might explain the production of X-ray emission lines. In this paper, we argue that this energy can come from a continuous postburst outflow. Focusing on a central engine of highly magnetized millisecond pulsar or magnetar, we find that the afterglow can be affected by the illuminating continuum, and therefore a distinct achromatic bump can be observed in the early afterglow light curves. With the luminosity of the continuous outflow that produces the line emission, we define the upper limit of the time when the bump feature appears. We argue that the reason why the achromatic bumps have not been detected so far is that the bumps appear at too early a time to be observed.

X-ray Emission Lines in GRB Afterglows: Evidence for a Two-component Jet Model

“…For GRB 011211 the energy for illuminating the reprocessing material obtained from the X-ray lines is higher than 5×10 50 ergs (Gao and Wei 2004;Ghisellini et al 2002), which is higher than that of the γ-ray bursts. In this case, the wide component will dominate the afterglow, a bump will appear in the lightcurve of the afterglow.…”

“…Later emission lines were also detected in the X-ray afterglows of GRB 970828 (Yoshida et al 2001) with ASCA; GRB 991216 (Piro et al 2000) and GRB020813 (Butler et al 2003) with Chandra; GRB 011211 (Reeves et al 2002), GRB 001025A (Watson et al 2002) and GRB 030227 (Watson et al 2003) with XMM-Newton; GRB 000214 (Antonelli et al 2000) with BeppoSAX. The detailed properties of the X-ray emission features can be found in several papers ( Lazzati 2002;Böttcher 2003;Gao & Wei 2004 ). The locations of the emission lines found in the X-ray afterglows of GRB 970508, GRB 970828, GRB 991216 and GRB 000214 are roughly consistent with Fe K α at the redshift of the hosts, while the emission lines were identified as blueshifted light elements lines of S, Si, Ar, Mg, and Ca in the afterglow of GRB 011211, GRB 020813 and GRB 030227.…”

“…In ED models, the lines are created by reprocessing material very close to the explosion site(R∼ 10 13 cm). The ionizing continuum is believed to be provided by a post-burst energy injection (Rees & Mészáros 2000;Mészáros & Rees 2001;Gao & Wei 2004, 2005. The duration of the lines emission is determined by the time interval of the post-burst energy injection.…”

A New Model for Iron Emission Lines and Rebursts in Gamma‐Ray Burst X‐Ray Afterglows

“…Later emission lines were also detected in the X-ray afterglows of GRB 970828 (Yoshida et al 2001) with ASCA; GRB 991216 (Piro et al 2000) and GRB 020813 (Butler et al 2003) with Chandra; GRB 011211 (Reeves et al 2002), GRB 001025A ( Watson et al 2002), and GRB 030227 ( Watson et al 2003) with XMM-Newton; and GRB 000214 (Antonelli et al 2000) with BeppoSAX. The detailed properties of the X-ray emission features can be found in several papers (Lazzati 2002;Böttcher 2003;Gao & Wei 2004). The energy of the emission line found in the X-ray afterglows of GRB 970508, GRB 970828, GRB 991216, and GRB 000214 is roughly consistent with Fe K at the redshift of the hosts.…”

“…The energy contained in the illuminating continuum that is responsible for the line production is much higher than that of the collimated GRBs Ghisellini et al 2002;Gao & Wei 2004). In this letter we consider the illuminating continuum which produces the emission line comes from the delayed injection energy , which illuminates the fallback disk and produces the emission lines.…”