Determining the Efficiency of Converting Magnetar Spindown Energy into Gamma-Ray Burst X-Ray Afterglow Emission and Its Possible Implications

Xiao, Di; Dai, Z. G.

doi:10.3847/1538-4357/ab12da

Cited by 38 publications

(30 citation statements)

References 58 publications

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“…In this work, we have focussed on the simple case of a precessing dipole. A more thorough analysis would include additional terms in (2) from neutrino-driven mass losses (Thompson, Chang & Quataert 2004), gravitational radiation (Lasky & Glampedakis 2016), multipolar magnetic fields (Mastrano, Suvorov & Melatos 2015), and possible fall-back accretion (Melatos & Priymak 2014), all of which would modify the braking index n of the neutron star and help explain the inferred values 3 n 5 for various GRB remnants (Xiao & Dai 2019;Lü, Lan & Liang 2019). In a plasma-filled magnetosphere, the braking index reads n ≈ 3 + 2 sin 2 α cos 2 α 1 + sin 2 α −2 (Arzamasskiy, Philippov & Tchekhovskoy 2015), which is generally greater than 3 though fluctuates as α wobbles in a precessing model.…”

Section: Discussionmentioning

confidence: 99%

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Evidence for Magnetar Precession in X-Ray Afterglows of Gamma-Ray Bursts

Suvorov

Kokkotas

2020

ApJL

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Many gamma-ray bursts are followed by periods of extended emission. At least in some cases, the burst afterglow may be powered by a rapidly rotating, highly-magnetised neutron star, which spins down due to electromagnetic and gravitational wave emission. Such a remnant is likely to strongly precess in the early stages of its life, which would lead to modulations in the X-ray luminosity as the triaxiality of the system evolves over time. Using a radiation profile appropriate for a precessing, oblique rotator, we find that Swift-XRT data of a long (080602) and a short (090510) burst matches the model with significantly higher accuracy (mean-square residuals dropping by 200% in the early stages of the extended emission) than for an orthogonal rotator. We interpret this as evidence for precession in newborn magnetars.

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Section: Discussionmentioning

confidence: 99%

“…where η ≤ 1 is an efficiency parameter accounting for imperfect conversion [see e.g. Xiao & Dai (2019)]. If the newborn star is an oblique rotator with millisecond period and strong ( 10 15 G) magnetic field, the dominant term within L may be sourced by electromagnetic braking.…”

Section: Millisecond Magnetar Engines For Grbsmentioning

confidence: 99%

Evidence for Magnetar Precession in X-Ray Afterglows of Gamma-Ray Bursts

Suvorov

Kokkotas

2020

ApJL

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“…We place a set of initial values to minimize the function with the iminuit interface and the migrad optimizer. We assume a fallback mass of M fb = 0.8 M e (Metzger et al 2018) and η x = 0.1 (Bernardini et al 2013;Xiao & Dai 2019). We report the best-fit values of the magnetic field, spin period, and fallback timescale in Table 7.…”

Section: Modeling the Multiwavelength Light Curvesmentioning

confidence: 99%

On the Origin of the Multi-GeV Photons from the Closest Burst with Intermediate Luminosity: GRB 190829A

Fraija

Vereš

Beniamini

et al. 2021

ApJ

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Very high energy (VHE) emission is usually interpreted in the synchrotron self-Compton scenario and expected from the low-redshift and high-luminosity gamma-ray bursts (GRBs), such as GRB 180720B and GRB 190114C. Recently, the H.E.S.S. telescopes reported VHE emission from one of the closest bursts, GRB 190829A, which was associated with the supernova 2019oyw. In this paper, we present a temporal and spectral analysis from optical bands to the Fermi-LAT energy range over multiple observational periods beginning after the trigger time and extending for almost 3 months. We show that the X-ray and optical observations are consistent with synchrotron forward-shock emission evolving between the characteristic and cooling spectral breaks during the early and late afterglow in a uniform-density medium. Modeling the light curves together with the spectral energy distribution, we show that the outflow expanded with an initial bulk Lorentz factor of Γ ∼ 30, which is high for low-luminosity GRBs and low for high-luminosity GRBs. The values of the initial bulk Lorentz factor and the isotropic-equivalent energy suggest that GRB 190829A is an intermediate-luminosity burst; consequently, it becomes the first burst of this class to be detected in the VHE gamma-ray band by an imaging atmospheric Cherenkov telescope and, in turn, the first event to not be simultaneously observed by the Fermi-LAT instrument. Analyzing the intermediateluminosity bursts with z  0.2, such as GRB 130702A, we show that bursts with intermediate luminosities are potential candidates to be detected in VHEs.

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“…The alignment and magnetic dipole moment decline of a newborn magnetar in the early stage may result in the braking index evolution, and its value can be greater than 3 (S ¸aşmaz Muş et al 2019). The n value may also be slightly greater than 3 when the radiation efficiency decreases with time (Xiao & Dai 2019). Alternately, Metzger et al (2018) suggested that the fall-back accretion may lead to n < 3.…”

Section: Braking Indexmentioning

confidence: 99%

“…The radiation efficiency is quite uncertain. Xiao & Dai (2019) showed η as a function of L k for different bulk saturation Lorentz factors (Γ sat ) of the DR wind. The efficiency dramatically increases with the decrease of the Γ sat value.…”

Section: Initial Spin Period and Magnetic Field Strengthmentioning

confidence: 99%

Comparison of the Characteristics of Magnetars Born in Death of Massive Stars and Merger of Compact Objects With {\em Swift} Gamma-Ray Burst Data

Zou,

Liang,

Zhong

et al. 2021

Preprint

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Assuming that the shallow-decaying phase in the early X-ray lightcurves of gamma-ray bursts (GRBs) is attributed to the dipole radiations (DRs) of a newborn magnetar, we present a comparative analysis for the magnetars born in death of massive stars and merger of compact binaries with long and short GRB (lGRB and sGRB) data observed with the Swift mission. We show that the typical braking index (n) of the magnetars is ∼ 3 in the sGRB sample, and it is ∼ 4 for the magnetars in the lGRB sample. Selecting a sub-sample of the magnetars whose spin-down is dominated by DRs (n 3) and adopting a universal radiation efficiency of 0.3, we find that the typical magnetic field strength (B p ) is 10 16 G vs. 10 15 G and the typical initial period (P 0 ) is ∼ 20 ms vs. 2 ms for the magnetars in the sGRBs vs. lGRBs. They follow the same relation between P 0 and the isotropic GRB energy as P 0 ∝ E −0.4 jet . We also extend our comparison analysis to superluminous supernovae (SLSNe) and stable pulsars. Our results show that a magnetar born in merger of compact stars tends to have a stronger B p and a longer P 0 by about one order of magnitude than that born in collapse of massive stars. Its spin-down is dominated by the magnetic DRs as old pulsars, being due to its strong magnetic field strength, whereas the early spin-down of magnetars born in massive star collapse is governed by both the DRs and gravitational wave (GW) emission. A magnetar with a faster rotation speed should power a more energetic jet, being independent of its formation approach.

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Determining the Efficiency of Converting Magnetar Spindown Energy into Gamma-Ray Burst X-Ray Afterglow Emission and Its Possible Implications

Cited by 38 publications

References 58 publications

Evidence for Magnetar Precession in X-Ray Afterglows of Gamma-Ray Bursts

Evidence for Magnetar Precession in X-Ray Afterglows of Gamma-Ray Bursts

On the Origin of the Multi-GeV Photons from the Closest Burst with Intermediate Luminosity: GRB 190829A

Comparison of the Characteristics of Magnetars Born in Death of Massive Stars and Merger of Compact Objects With {\em Swift} Gamma-Ray Burst Data

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