The unusual X-ray emission of the short Swift GRB 090515: evidence for the formation of a magnetar?

Rowlinson, A.; O’Brien, P. T.; Tanvir, N. R.; Zhang, Bing; Evans, P. A.; Lyons, N.; Levan, A. J.; Willingale, R.; Page, K. L.; Önal, Ö.; Burrows, D. N.; Beardmore, A. P.; Ukwatta, T. N.; Berger, E.; Hjorth, J.; Fruchter, A. S.; Tunnicliffe, Rachel; Fox, D. B.; Cucchiara, Antonino

doi:10.1111/j.1365-2966.2010.17354.x

Cited by 225 publications

(256 citation statements)

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“…Using a large sample of X-ray afterglow light curves, Lü et al (2015) came to the similar conclusion that NS mergers likely result in supramassive NSs. If the total energy constraints from our observations were uniformly more stringent, 10 52 erg, the collapse to a BH should be relatively abrupt (i.e., during the plateau phase itself), and we would expect more events with dramatic drops in their X-ray light curves, similar to GRB 090515 (Rowlinson et al 2010a).…”

Section: Discussionmentioning

confidence: 99%

“…Several studies have fit magnetar models to short GRBs with extended emission (Gompertz et al 2013), X-ray and optical plateaus (Rowlinson et al 2010aGompertz et al 2015;Lü et al 2015), and late-time excess emission (Fan et al 2013;Fong et al 2014), resulting in inferred spin periods of ≈1-10 ms and large magnetic fields of ≈(2-40)×10 15 G. As an alternative to the magnetar model, other energy sources remain energetically viable: most notably, late-time "fall-back" accretion onto the remnant black hole (Rosswog 2007;Kumar et al 2008;Cannizzo et al 2011). In order to substantiate the magnetar scenario for this subset of short GRBs, and also provide crucial insight on the NS EOS, it is necessary to test additional predictions of the magnetar model.…”

Section: Introductionmentioning

confidence: 99%

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Radio Constraints on Long-Lived Magnetar Remnants in Short Gamma-Ray Bursts

Fong

Metzger

Berger

et al. 2016

ApJ

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The merger of a neutron star (NS) binary may result in the formation of a rapidly spinning magnetar. The magnetar can potentially survive for seconds or longer as a supramassive NS before collapsing to a black hole if, indeed, it collapses at all. During this process, a fraction of the magnetar's rotational energy of ∼10 53 erg is transferred via magnetic spin-down to the surrounding ejecta. The resulting interaction between the ejecta and the surrounding circumburst medium powers a year-long or greater synchrotron radio transient. We present a search for radio emission with the Very Large Array following nine short-duration gamma-ray bursts (GRBs) at rest-frame times of ≈1.3-7.6 yr after the bursts, focusing on those events that exhibit early-time excess X-ray emission that may signify the presence of magnetars. We place upper limits of 18-32 μJy on the 6.0 GHz radio emission, corresponding to spectral luminosities of (0.05-8.3)×10 39 erg s −1 . Comparing these limits to the predicted radio emission from a long-lived remnant and incorporating measurements of the circumburst densities from broadband modeling of short GRB afterglows, we rule out a stable magnetar with an energy of 10 53 erg for half of the events in our sample. A supramassive remnant that injects a lower rotational energy of 10 52 erg is ruled out for a single event, GRB 050724A. This study represents the deepest and most extensive search for long-term radio emission following short GRBs to date, and thus the most stringent limits placed on the physical properties of magnetars associated with short GRBs from radio observations.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Radio Constraints on Long-Lived Magnetar Remnants in Short Gamma-Ray Bursts

Fong

Metzger

Berger

et al. 2016

ApJ

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“…With the discovery of the X-ray plateau (Rowlinson et al 2010(Rowlinson et al , 2013 and extended emission, the double neutron star merger is of particular interest because it provides the possibility to inject additional energy (Dai & Lu 1998a,b;Zhang & Mészáros 2001) to the ejecta under the assumption that the merger remnant is a magnetar that avoids collapse for an astrophysically interesting period (Dai et al 2006;Zhang 2013). …”

Section: Introductionmentioning

confidence: 99%

Reverse shock emission driven by post-merger millisecond magnetar winds: Effects of the magnetization parameter

Liu

Wang

Dai

2016

A&A

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The study of short-duration gamma-ray bursts provides growing evidence that a good fraction of double neutron star mergers lead to the formation of stable millisecond magnetars. The launch of Poynting flux by the millisecond magnetars could leave distinct electromagnetic signatures that reveal the energy dissipation processes in the magnetar wind. In previous studies, we assume that the magnetar wind becomes completely lepton-dominated so that electrons/positrons in the magnetar wind are accelerated by a diffusive shock. However, theoretical modeling of pulsar wind nebulae shows that in many cases the magnetic field energy in the pulsar wind may be strong enough to suppress diffusive shock acceleration. In this paper, we investigate the reverse shock emission and the forward shock emission with an arbitrary magnetization parameter σ of a magnetar wind. We find that the reverse shock emission strongly depends on σ, and in particular that σ ∼ 0.3 leads to the strongest reverse shock emission. Future observations would be helpful to diagnose the composition of the magnetar wind.

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“…These two sets of observational facts strongly suggest that supramassive magnetars are likely the remnants of a good fraction of double neutron star mergers. The internal energy dissipation of the Poynting-flux dominated outflow launched by the newly-formed millisecond magnetar before its collapse may power a high energy transient which accounts for the peculiar X-ray emission (i.e., unexpected in the external forward shock model) following short bursts [14], in particular the X-ray plateau last-ing ∼ 100 s followed by an abrupt cease [18].…”

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confidence: 99%

Signature of gravitational wave radiation in afterglows of short gamma-ray bursts?

Fan

Wei

2013

Phys. Rev. D

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Short Gamma-Ray Bursts (GRBs), brief intense emission of γ−rays characterized by a duration shorter than 2 seconds that are plausibly powered by the coalescence of binary neutron stars, are believed to be strong gravitational wave radiation (GWR) sources. The test of such a speculation has been thought to be impossible until the performance of the detectors like advanced LIGO. Recently there has been growing evidence for the formation of highly-magnetized neutron star (i.e., magnetar) in the double neutron star mergers. In this work we re-examine the interpretation of the X-ray plateau followed by an abrupt decline detected in some short GRB afterglows within the supramassive magnetar model and find that the maximum gravitational mass of the non-rotating neutron stars is ∼ 2.3M⊙ and the observed duration of some X-ray plateaus are significantly shorter than that expected in the magnetic dipole radiation scenario, suggesting that the collapse of the supramassive magnetars has been considerably enhanced by the energy loss via GWR. Such a result demonstrates that the signature of GWR may have already existed in current electromagnetic data of short GRBs.PACS numbers: 98.70. Rz, Thanks to the successful performance of the Swift satellite, our understanding of short GRBs, a kind of γ−ray outbursts with a duration less than two seconds [1], has been revolutionized [2]. At least for some short GRBs, the binary-neutron-star merger model [3] has been supported by their host galaxy properties and by the non-association with bright supernovae [4,5]. The coalescence of double neutron stars inevitably produces an energetic burst of gravitational radiation, which is expected to be one of the most promising targets for current and the proposed future gravitational wave detectors [6]. Moreover gravitational wave detection, in principle, is able to pin down the nature of the remnant of the merger, either a stellar mass black hole or a neutron star. Though the prospects are promising, so far direct detection of gravitational wave radiation (GWR) is not obtained yet and people are looking forward to the performance of detectors like advanced LIGO. However, we'll show in this short work that identifying GWR signature in current electromagnetic data of short GRBs is already possible.In the relativistic simulations of double neutron star merger with a total gravitational mass M tot ∼ 2.6 − 2.8 M ⊙ , initially a differentially-rotating heavy neutron star is formed [7][8][9][10]. The magnetic braking and viscosity combine to drive the star to uniform rotation within a time t diff ∼ 0.1 − 1 s if the surface magnetic field strength of the star reaches 10 14 − 10 15 G [11] and the magnetic activity of the initial differentiallyrotating neutron star is likely able to drive brief energetic γ−ray outburst and thus account for the short GRB [9]. The uniform rotation period of the heavy neutron star is P 0 ∼ 1 ms ([10], following [12] one can also show analytically that it is the case). The rapid rotation can enhance the maximum gravitational ...

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The unusual X-ray emission of the short Swift GRB 090515: evidence for the formation of a magnetar?

Cited by 225 publications

References 73 publications

Radio Constraints on Long-Lived Magnetar Remnants in Short Gamma-Ray Bursts

Radio Constraints on Long-Lived Magnetar Remnants in Short Gamma-Ray Bursts

Reverse shock emission driven by post-merger millisecond magnetar winds: Effects of the magnetization parameter

Signature of gravitational wave radiation in afterglows of short gamma-ray bursts?

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