Statistical Study of the Swift X-Ray Flash and X-Ray Rich Gamma-Ray Bursts

ABSTRACT The spin-down energy of millisecond magnetars has been invoked to explain X-ray afterglow observations of a significant fraction of short and long gamma-ray bursts. Here, we extend models previously introduced in the literature, incorporating radiative losses with the spin-down of a magnetar central engine through an arbitrary braking index. Combining this with a model for the tail of the prompt emission, we show that our model can better explain the data than millisecond-magnetar models without radiative losses or those that invoke spin-down solely through vacuum dipole radiation. We find that our model predicts a subset of X-ray flares seen in some gamma-ray bursts. We can further explain the diversity of X-ray plateaus by altering the radiative efficiency and measure the braking index of newly born millisecond magnetars. We measure the braking index of GRB061121 as $n=4.85^{+0.11}_{-0.15}$ suggesting the millisecond-magnetar born in this gamma-ray burst spins down predominantly through gravitational-wave emission.

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Spectral Characteristics of X-Ray Flashes Compared to Gamma-Ray Bursts

10.1063/1.1579349 ◽

2003 ◽

Cited By ~ 19

Author(s):

R. M. Kippen

Keyword(s):

Gamma Ray ◽

Spectral Characteristics ◽

Gamma Ray Bursts ◽

X Ray

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Search for X-ray afterglows from gamma-ray bursts in the RASS

10.1063/1.1361566 ◽

2000 ◽

Author(s):

J. Greiner

Keyword(s):

Gamma Ray ◽

Gamma Ray Bursts ◽

X Ray

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Diverse Features of the Multiwavelength Afterglows of Gamma-Ray Bursts: Natural or Special?

Advances in Astronomy ◽

10.1155/2016/1592148 ◽

2016 ◽

Vol 2016 ◽

pp. 1-10 ◽

Cited By ~ 4

Author(s):

J. J. Geng ◽

Y. F. Huang

Keyword(s):

Black Holes ◽

Numerical Method ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

Shock Model ◽

Reverse Shock ◽

X Ray ◽

Electron Positron ◽

Forward Shock ◽

Electron Positron Pair

The detection of optical rebrightenings and X-ray plateaus in the afterglows of gamma-ray bursts (GRBs) challenges the generic external shock model. Recently, we have developed a numerical method to calculate the dynamics of the system consisting of a forward shock and a reverse shock. Here, we briefly review the applications of this method in the afterglow theory. By relating these diverse features to the central engines of GRBs, we find that the steep optical rebrightenings would be caused by the fall-back accretion of black holes, while the shallow optical rebrightenings are the consequence of the injection of the electron-positron-pair wind from the central magnetar. These studies provide useful ways to probe the characteristics of GRB central engines.

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X-ray afterglows of Gamma-Ray bursts

10.1063/1.1434643 ◽

2001 ◽

Cited By ~ 1

Author(s):

Luigi Piro

Keyword(s):

Gamma Ray ◽

Gamma Ray Bursts ◽

X Ray

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Swift observations of gamma-ray bursts

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2006.1975 ◽

2007 ◽

Vol 365 (1854) ◽

pp. 1119-1128 ◽

Cited By ~ 2

Author(s):

Neil Gehrels

Keyword(s):

Gamma Ray ◽

High Redshift ◽

Gamma Ray Bursts ◽

Optical Observations ◽

Nearby Galaxy ◽

X Ray ◽

Star Forming ◽

Star Forming Regions ◽

Other Information ◽

Short Grbs

Since its launch on 20 November 2004, the Swift mission has been detecting approximately 100 gamma-ray bursts (GRBs) each year, and immediately (within approx. 90 s) starting simultaneous X-ray and UV/optical observations of the afterglow. It has already collected an impressive database, including prompt emission to higher sensitivities than BATSE, uniform monitoring of afterglows and a rapid follow-up by other observatories notified through the GCN. Advances in our understanding of short GRBs have been spectacular. The detection of X-ray afterglows has led to accurate localizations and the conclusion that short GRBs can occur in non-star-forming galaxies or regions, whereas long GRBs are strongly concentrated within the star-forming regions. This is consistent with the NS merger model. Swift has greatly increased the redshift range of GRB detection. The highest redshift GRBs, at z ∼5–6, are approaching the era of reionization. Ground-based deep optical spectroscopy of high redshift bursts is giving metallicity measurements and other information on the source environment to a much greater distance than other techniques. The localization of GRB 060218 to a nearby galaxy, and the association with SN 2006aj, added a valuable member to the class of GRBs with detected supernova.

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