Evidence for a Canonical GRB Afterglow Light Curve in the Swift/XRT Data

Nousek, J. A.; Mangano, V.; O’Brien, P. T.; Giommi, P.; Godet, O.; Barthelmy, S. D.; Goad, M. R.; Campana, S.; Cusumano, G.; Osborne, J.; Beardmore, A. P.; Falcone, A.; Granot, Jonathan; Tagliaferri, G.; Capalbi, M.; Burrows, D. N.; Romano, P.; Hurkett, C.; Kennea, J. A.; Chincarini, G.; Grupe, D.; Ramírez-Ruiz, E.; Patel, Sandy K.; Page, K. L.; Wells, A.; Kouveliotou, C.; Moretti, A.; Gehrels, N.

doi:10.2172/878781

Cited by 53 publications

(94 citation statements)

References 46 publications

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“…Here we report on Swift observations of GRB050126 and GRB050219A (see also Tagliaferri et al 2005;Nousek et al 2005;, for a discussion of the average early X-ray light-curve behaviour of a sample of Swift detected GRBs), two bursts for which we have early observations (within ∼100 s) in the XRT and which show similar behaviour in their prompt X-ray light-curves. In Sect.…”

Section: Introductionmentioning

confidence: 92%

Swift observations of the prompt X-ray emission and afterglow from GRB050126 and GRB050219A

Goad¹,

Tagliaferri

Page³

et al. 2006

A&A

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We report on the temporal and spectral characteristics of the early X-ray emission from the Gamma Ray Bursts GRB050126 and GRB050219A as observed by Swift. The X-ray light-curves of these 2 bursts both show remarkably steep early decays (F(t) ∝ t −3 ), breaking to flatter slopes on timescales of a few hundred seconds. For GRB050126 the burst shows no evidence of spectral evolution in the 20-150 keV band, and the spectral index of the γ-ray and X-ray afterglows are significantly different suggesting a separate origin. By contrast the BAT spectrum of GRB050219A displays significant spectral evolution, becoming softer at later times, with Γ evolving toward the XRT photon index seen in the early X-ray afterglow phase. For both bursts, the 0.2-10 keV spectral index pre-and post-break in the X-ray decay light-curve are consistent with no spectral evolution. We suggest that the steep early decline in the X-ray decay light-curve is either the curvature tail of the prompt emission; X-ray flaring activity; or external forward shock emission from a jet with high density regions of small angular size (>Γ −1 ). The late slope we associate with the forward external shock.

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Section: Introductionmentioning

confidence: 92%

Swift observations of the prompt X-ray emission and afterglow from GRB050126 and GRB050219A

Goad¹,

Tagliaferri

Page³

et al. 2006

A&A

Self Cite

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“…1 in Nousek et al, 2005) (at about 3000s, there is a steep decay). However, GRB 050315 (Vaughan et al, 2005) can be classified into the case that "normal" afterglow exceed the shallow tail emission before the tail emission breaks to steep phase.…”

Section: Shallow Decay Of Early X-ray Afterglowmentioning

confidence: 97%

“…Considering the zero point effect of time, the light curves can be steeper during a short period (Nousek et al, 2005;Zhang et al, 2005;Wu et al, 2006). Nousek et al (2005) and Zhang et al (2005) have also shown that a shallow decay with index of about −1/2 follows the steep decay for most X-ray afterglows. For the Xray afterglow of short burst GRB 050709, there is an unexpected high-flux point followed by a very steep decay (Fox et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Tail Emission from a Ring-like Jet: Its Application to Shallow Decays of Early Afterglows and GRB 050709

Zou

Dai

2006

Chin. J. Astron. Astrophys.

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Similar to the pulsar, the magnetic axis and the spin axis of the gamma-ray burst source may not lie on the same line. This may cause a ring-like jet due to collimation of the precessing magnetic axis. We analyze the tail emission from such a jet, and find that it has a shallow decay phase with temporal index equal to −1/2 if the Lorentz factor of the ejecta is not very high. This phase is consistent with the shallow decay phase of some early X-ray afterglow detected by swift. The ring-like jet has a tail cusp with sharp rising and very sharp decay. This effect can provide an explanation for the re-brightening and sharp decay of the X-ray afterglow of GRB 050709.

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“…A systematic analysis of their light curves has evidenced several common features (Nousek et al, 2005;Chincarini et al, 2005). During the first few hundred seconds, a steep decay is often observed (α ≈ 3-5; Tagliaferri et al, 2005a), usually interpreted as the tail emission from the prompt GRB (e.g.…”

Section: The X-ray Light Curvementioning

confidence: 98%

“…During the first year of operation, Swift has observed some 75 GRB afterglows, already doubling the pre-Swift sample. This rich dataset has allowed to study in detail the X-ray light curves, both at early and late times, leading to the discovery of a complex behaviour (e.g Tagliaferri et al, 2005a;Nousek et al, 2005;Chincarini et al, 2005;Cusumano et al, 2005a). Coupled with optical data, either from UVOT (e.g.…”

Section: Introductionmentioning

confidence: 99%

Swift and XMM observations of the dark GRB 050326

Moretti¹,

Luca²,

Malesani³

et al. 2006

AIP Conference Proceedings

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Abstract. We present Swift and XMM-Newton observations of the bright gamma-ray burst GRB 050326, detected by the Swift Burst Alert Telescope. The Swift X-Ray Telescope (XRT) and XMM-Newton discovered and the X-ray afterglow beginning 54 min and 8.5 hr after the burst, respectively. The prompt GRB 050326 fluence was (7.7 ± 0.9) × 10 −6 erg cm −2 (20-150 keV), and its spectrum was hard, with a power law photon index Γ = 1.25 ± 0.03. The X-ray afterglow was quite bright, with a flux of 7 × 10 −11 erg cm −2 s −1 (0.3-8 keV), 1 hr after the burst. Its light curve did not show any break nor flares between ∼ 1 hr and ∼ 6 d after the burst, and decayed with a slope α = 1.70 ± 0.05. The afterglow spectrum is well fitted by a powerlaw model, suffering absorption both in the Milky Way and in the host galaxy. The rest-frame Hydrogen column density is significant, N H,z > ∼ 4 × 10 21 cm −2 , and the redshift of the absorber was constrained to be z > 1.5. There was good agreement between the spatial, temporal, and spectral parameters as derived by Swift-XRT and XMM-Newton. By comparing the prompt and afterglow fluxes, we found that an early break probably occurred before the beginning of the XRT observation, similarly to many other cases observed by Swift. However, the properties of the GRB 050326 afterglow are well described by a spherical fireball expanding in a uniform external medium, so a further steepening is expected at later times. The lack of such a break allowed us to constrain the jet half-opening angle ϑ j > ∼ 7• . Using the redshift constraints provided by the X-ray analysis, we also estimated that the beaming-corrected gamma-ray energy was larger than 3 × 10 51 erg, at the high end of GRB energies. Despite the brightness in X rays, only deep limits could be placed by Swift-UVOT at optical and ultraviolet wavelengths. Thus, this GRB was a "truly dark" event, with the optical-to-X-ray spectrum violating the synchrotron limit. The optical and X-ray observations are therefore consistent either with an absorbed event or with a high-redshift one. To obey the Ghirlanda relation, a moderate/large redshift z > ∼ 4.5 is required.

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Evidence for a Canonical GRB Afterglow Light Curve in the Swift/XRT Data

Cited by 53 publications

References 46 publications

Swift observations of the prompt X-ray emission and afterglow from GRB050126 and GRB050219A

Swift observations of the prompt X-ray emission and afterglow from GRB050126 and GRB050219A

Tail Emission from a Ring-like Jet: Its Application to Shallow Decays of Early Afterglows and GRB 050709

Swift and XMM observations of the dark GRB 050326

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