A Possible Kilonova Powered by Magnetic Wind from a Newborn Black Hole

Ma, Shuai-Bing; Xie, Wei; Liao, Bin; Zhang, Bin-Bin; Lü, Hou-Jun; Liu, Yu; Lei, Wei‐Hua

doi:10.3847/1538-4357/abe71b

Cited by 9 publications

(7 citation statements)

References 62 publications

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“…1), which indicated that a post-merger NS also exists in this event. According to these observations, Ma et al (2021) suggested that the post-merger NS could collapse into a black hole and then the subsequent kilonova could be powered by the accretion onto the black hole. Nevertheless, alternatively, as suggested by Yu et al (2018), the steep decay after the internal plateau may not represent the collapse of the NS, but may simply be caused by the suppression of the mag-1 The reason for this judgement is that the neutrino emission from the remnant NS can suppress the synthesization of lanthanides in part of the merger ejecta and reduce its opacity.…”

Section: Introductionmentioning

confidence: 99%

Does a long-lived remnant neutron star exist after short gamma-ray burst GRB 160821B?

Zhu

2021

A&A

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Mergers of double neutron stars (DNSs) could lead to the formation of a long-lived massive remnant NS, which has been previously suggested to explain the AT 2017gfo kilonova emission in the famous GW170817 event. For an NS-affected kilonova, it is expected that a nonthermal emission component can be contributed by a pulsar wind nebula (PWN), which results from the interaction of the wind from the remnant NS with the preceding merger ejecta. Therefore, the discovery of such a nonthermal PWN emission would provide evidence for the existence of the remnant NS. Similar to GRB 170817A, GRB 160821B is also one of the nearest short gamma-ray bursts (SGRBs). A candidate kilonova is widely believed to appear in the ultraviolet–optical–infrared afterglows of GRB 160821B. Here, by modeling the afterglow light curves and spectra of GRB 160821B, we find that invoking nonthermal PWN emission can indeed be highly consistent with the observational data. This may indicate that the formation of a stable massive NS is not uncommon in DNS merger events, and therefore that the equation of state of the post-merger NSs should be stiff enough.

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Section: Introductionmentioning

confidence: 99%

Does a long-lived remnant neutron star exist after short gamma-ray burst GRB 160821B?

Zhu

2021

A&A

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“…To date, except for AT2017gfo, other kilonova candidates were all detected in superposition with decaying sGRB afterglows (e.g., Berger et al 2013;Tanvir et al 2013;Fan et al 2013;Gao et al 2015Gao et al , 2017Jin et al 2015Jin et al , 2016Jin et al , 2020Yang et al 2015;Gompertz et al 2018;Ascenzi et al 2019;Rossi et al 2020;Ma et al 2021;Fong et al 2021;Wu et al 2021;Yuan et al 2021). One possible reason is that most BNS and NSBH mergers are far away from us.…”

Section: Introductionmentioning

confidence: 99%

Kilonova and Optical Afterglow from Binary Neutron Star Mergers. II. Optimal Search Strategy for Serendipitous Observations and Target-of-opportunity Observations of Gravitational-wave Triggers

Zhu¹,

Wu²,

Yang³

et al. 2021

Preprint

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In the second work of this series, we explore the optimal search strategy for serendipitous and gravitational-wave-triggered target-of-opportunity observations of kilonovae and optical short-duration gamma-ray burst (sGRB) afterglows from binary neutron star (BNS) mergers, assuming that cosmological kilonovae are AT2017gfo-like (but with viewing-angle dependence) and that the properties of afterglows are consistent with those of cosmological sGRB afterglows. A one-day cadence serendipitous search strategy with an exposure time of ∼ 30 s can always achieve an optimal search strategy of kilonovae and afterglows for various survey projects. We show that the optimal detection rates of the kilonova-dominated (afterglow-dominated) events are ∼ 0.2/0.5/0.8/20 yr −1 (∼ 500/300/600/3000 yr −1 ) for ZTF/Mephisto/WFST/LSST, respectively. A better search strategy for SiTian is to increase the exposure time. SiTian can find ∼ 5(6000) yr −1 kilonova-dominated (afterglow-dominated) events. We predict abundant off-axis orphan afterglows may be recorded in the survey database although not been identified. For target-of-opportunity observations, we simulate the maximum BNS gravitational-wave (GW) detection rates, which are ∼ 27/210/1800/2.0 × 10 5 yr −1 , in the networks of 2nd/2.5th/3rd(Voyager)/3rd(ET&CE)-generation GW detectors. In the upcoming 2nd-generation networks, follow-up observations with a limiting magnitude of m limit 22 − 23 mag can discover all EM signals from BNS GW events. Among these detected GW events, ∼ 60% events (∼ 16 yr −1 ) can detect clear kilonova signals, while afterglow-dominated events would account for the other ∼ 40% events (∼ 11 yr −1 ). In the 2.5th-and 3rd(Voyager)-generation era, the critical magnitudes for the detection of EM emissions from all BNS GW events would be ∼ 23.5 mag and ∼ 25 mag, respectively. Foreseeable optical survey projects cannot detect all EM signals of GW events detected during the ET&CE era.

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“…Despite many efforts for followup observations, no confirmed kilonova or afterglow candidate was identified (e.g., Coughlin et al 2020a;Anand et al 2021), which may suggest that the two NSBH merger events were plunging events without tidal disruption of the NSs (Zhu et al 2021d(Zhu et al , 2022Abbott et al 2021;Gompertz et al 2022). In addition to AT2017gfo, some kilonova candidates have been claimed to be superposed on the decaying sGRB afterglows in the past few years (e.g., Berger et al 2013;Fan et al 2013;Tanvir et al 2013;Gao et al 2015Gao et al , 2017Jin et al 2015Jin et al , 2016Jin et al , 2020Yang et al 2015;Lamb et al 2019b;Troja et al 2019;Fong et al 2021;Ma et al 2021;Wu et al 2021;Yuan et al 2021). Two main criteria were used to identify the kilonova candidates: 1. a significant excess in optical flux with respect to the sGRB optical afterglow light curve, and 2. the existence of a color evolution of the kilonova emission as compared with the nonevolving color of the sGRB afterglow emission.…”

Section: Introductionmentioning

confidence: 99%

Kilonova and Optical Afterglow from Binary Neutron Star Mergers. I. Luminosity Function and Color Evolution

Zhu

Yang

Zhang

et al. 2022

ApJ

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In the first work of this series, we adopt a GW170817-like viewing-angle-dependent kilonova model and the standard afterglow model with a light-curve distribution based on the properties of cosmological short gamma-ray burst afterglows to simulate the luminosity functions and color evolution of both kilonovae and optical afterglow emissions from binary neutron star (BNS) mergers. We find that ∼10% of the nearly-on-axis afterglows are brighter than the associated kilonovae at the peak time. These kilonovae would be significantly polluted by the associated afterglow emission. Only at large viewing angles with sin θ v ≳ 0.20 , the electromagnetic signals of most BNS mergers would be kilonova-dominated and some off-axis afterglows may emerge at ∼5–10 days after the mergers. At a brightness dimmer than ∼23–24 mag, according to their luminosity functions, the number of afterglows is much larger than that of kilonovae. Because the search depth of the present survey projects is <22 mag, the number of afterglow events that are detected via serendipitous observations would be much higher than that of kilonova events, consistent with the current observations. For the foreseeable survey projects (e.g., Mephisto, WFST, and LSST), whose search depths can reach ≳23–24 mag, the detection rate of kilonovae could have the same order of magnitude as afterglows. We also find that it may be difficult to use the fading rate in a single band to directly identify kilonovae and afterglows among various fast-evolving transients by serendipitous surveys. However, the color evolution between the optical and infrared bands can identify them because the color evolution patterns of these phenomena are unique compared with those of other fast-evolving transients.

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A Possible Kilonova Powered by Magnetic Wind from a Newborn Black Hole

Cited by 9 publications

References 62 publications

Does a long-lived remnant neutron star exist after short gamma-ray burst GRB 160821B?

Does a long-lived remnant neutron star exist after short gamma-ray burst GRB 160821B?

Kilonova and Optical Afterglow from Binary Neutron Star Mergers. II. Optimal Search Strategy for Serendipitous Observations and Target-of-opportunity Observations of Gravitational-wave Triggers

Kilonova and Optical Afterglow from Binary Neutron Star Mergers. I. Luminosity Function and Color Evolution

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