Brightening X-Ray/Optical/Radio Emission of GW170817/SGRB 170817A: Evidence for an Electron–Positron Wind from the Central Engine?

Geng, Jin-Jun; Dai, Z. G.; Huang, Yun‐Feng; Wu, Xue-Feng; Li, Longbiao; Li, Bing; Meng, Yan-Zhi

doi:10.3847/2041-8213/aab7f9

Cited by 37 publications

(35 citation statements)

References 130 publications

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“…We show that the multiband light curves of AT2017gfo can well be reproduced by such an engine-driven mergernova model, where both the opacity κ and the ejected mass values for both the blue and red components fall into the reasonable ranges of known numerical simulations. This enhances the suggestion (Yu et al 2018) of a long-lived NS as the merger remnant of GW170817 (see also Ai et al 2018;Geng et al 2018).…”

Section: Discussionsupporting

confidence: 70%

What Powered the Optical Transient AT2017gfo Associated with GW170817?

Liu

et al. 2018

ApJL

105

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The groundbreaking discovery of the optical transient AT2017gfo associated with GW170817 opens a unique opportunity to study the physics of double neutron star (NS) mergers. We argue that the standard interpretation of AT2017gfo as being powered by radioactive decays of r-process elements faces the challenge of simultaneously accounting for the peak luminosity and peak time of the event, as it is not easy to achieve the required high mass, and especially the low opacity of the ejecta required to fit the data. A plausible solution would be to invoke an additional energy source, which is probably provided by the merger product. We consider energy injection from two types of the merger products: (1) a post-merger black hole powered by fallback accretion; and (2) a long-lived NS remnant. The former case can only account for the early emission of AT2017gfo, with the late emission still powered by radioactive decay. In the latter case, both early-and late-emission components can be well interpreted as due to energy injection from a spinning-down NS, with the required mass and opacity of the ejecta components well consistent with known numerical simulation results. We suggest that there is a strong indication that the merger product of GW170817 is a long-lived (supramassive or even permanently stable), low magnetic field NS. The result provides a stringent constraint on the equations of state of NSs.

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Section: Discussionsupporting

confidence: 70%

What Powered the Optical Transient AT2017gfo Associated with GW170817?

Liu

et al. 2018

ApJL

105

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“…Such a NS has become more expectable since the discovery of two binary NS systems with total gravitational masses as low as ∼ 2.5M ⊙ (Martinez et al 2017;Stovall et al 2018). Following this argument, Geng et al (2018) fitted the late-time broadband afterglow of GW170817 very well.…”

Section: Analysis and Fittingmentioning

confidence: 86%

A Long-lived Remnant Neutron Star after GW170817 Inferred from Its Associated Kilonova

Liu

Dai

2018

ApJ

Self Cite

145

149

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The successful joint observation of the gravitational wave event GW170817 and its multi-wavelength electromagnetic counterparts first enables human to witness a definite merger event of two neutron stars (NSs). This historical event confirms the origin of short-duration gamma-ray bursts (GRBs), and in particular, identifies the theoretically-predicted kilonova phenomenon that is powered by radioactive decays of r-process heavy elements. However, whether a long-lived remnant NS could be formed during this merger event remains unknown, although such a central engine has been suggested by afterglow observations of some short-duration GRBs. By invoking this long-lived remnant NS, we here propose a model of hybrid energy sources for the kilonova AT2017gfo associated with GW 170817. While the early emission of AT2017gfo is still powered radioactively as usually suggested, its late emission is primarily caused by delayed energy injection from the remnant NS. In our model, only one single opacity is required and an intermediate value of κ ≃ 0.97 cm 2 g −1 is revealed, which could be naturally provided by lanthanide-rich ejecta that is deeply ionized by the emission from a wind of the NS. These self-consistent results indicate that a long-lived remnant NS, which must own a very stiff equation of state, had been formed during the merger event of GW170817. This provides a very stringent constraint on the strong interaction in nuclear-quark matter. It is further implied that such GW events could provide a probe of the early spin and magnetic evolutions of NSs, e.g., the burying of surface magnetic fields.

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“…From the EM observational side, circumstantial evidence points toward a short-lived hypermassive NS (Granot et al 2017(Granot et al , 2018Kasen et al 2017;Matsumoto et al 2018;Pooley et al 2018); though several authors (Ai et al 2018;Geng et al 2018;Li et al 2018;Yu et al 2018) have considered continued energy injection from a long-lived remnant NS. Given this inconclusive observational situation, we agnostically consider the possibility of GW emission from a long-lived remnant NS and seek here to constrain it from the LIGO data.…”

Section: Astrophysical Background and Waveform Modelmentioning

confidence: 99%

Search for Gravitational Waves from a Long-lived Remnant of the Binary Neutron Star Merger GW170817

Abbott

et al. 2019

ApJ

129

100

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One unanswered question about the binary neutron star coalescence GW170817 is the nature of its post-merger remnant. A previous search for post-merger gravitational waves targeted high-frequency signals from a possible neutron star remnant with a maximum signal duration of 500 s. Here, we revisit the neutron star remnant scenario and focus on longer signal durations, up until the end of the second Advanced LIGO-Virgo observing run, which was 8.5 days after the coalescence of GW170817. The main physical scenario for this emission is the power-law spindown of a massive magnetar-like remnant. We use four independent search algorithms with varying degrees of restrictiveness on the signal waveform and different ways of dealing with noise artefacts. In agreement with theoretical estimates, we find no significant signal candidates. Through simulated signals, we quantify that with the current detector sensitivity, nowhere in the studied parameter space are we sensitive to a signal from more than 168 Deceased, 2018 February. 169 Deceased, 2017 November.1 Mpc away, compared to the actual distance of 40 Mpc. However, this study serves as a prototype for post-merger analyses in future observing runs with expected higher sensitivity.

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Brightening X-Ray/Optical/Radio Emission of GW170817/SGRB 170817A: Evidence for an Electron–Positron Wind from the Central Engine?

Cited by 37 publications

References 130 publications

What Powered the Optical Transient AT2017gfo Associated with GW170817?

What Powered the Optical Transient AT2017gfo Associated with GW170817?

A Long-lived Remnant Neutron Star after GW170817 Inferred from Its Associated Kilonova

Search for Gravitational Waves from a Long-lived Remnant of the Binary Neutron Star Merger GW170817

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