Shock Breakout Driven by the Remnant of a Neutron Star Binary Merger: An X-Ray Precursor of Mergernova Emission

Li, Shao-Ze; Yu, Yun-Wei

doi:10.3847/0004-637x/819/2/120

Cited by 30 publications

(29 citation statements)

References 70 publications

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“…Combining Eqs. (1), (2), (5), (7), (10), and (11) and taking into account the tilt angle evolution in the second stage, we can determine the LCs (evolution of L th ) of magnetar-powered SLSNe. In all calculations below, typical values M ej = 5M ⊙ and κ = 0.2 cm 2 g −1 are taken for the ejecta mass and opacity, respectively [4,41].…”

Section: Resultsmentioning

confidence: 99%

Probing the physics of newly born magnetars through observation of superluminous supernovae

Cheng

Zhang

et al. 2018

Phys. Rev. D

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The central engines of some superluminous supernovae (SLSNe) are generally suggested to be newly born fast rotating magnetars, which spin down mainly through magnetic dipole radiation and gravitational wave emission. We calculate the magnetar-powered SLSNe light curves (LCs) with the tilt angle evolution of newly born magnetars involved. We show that, depending on the internal toroidal magnetic fieldsB t , the initial spin periods P i , and the radii R DU of direct Urca (DU) cores of newly born magnetars, as well as the critical temperature T c for 3 P 2 neutron superfluidity, bumps could appear in the SLSNe LCs after the maximum lights when the tilt angles grow to π/2. The value of T c determines the arising time and the relative amplitude of a bump. The quantity R DU can affect the arising time and the luminosity of a bump, as well as the peak luminosity of a LC. For newly born magnetars with dipole magnetic fields B d = 5 × 10 14 G,B t = 4.6 × 10 16 G, and P i = 1 ms, there are no bumps in the LCs if T c = 2 × 10 9 K, or R DU = 1.5 × 10 5 cm. Moreover, it is interesting that a stronger B t will lead to both a brighter peak and a brighter bump in a LC. While keeping other quantities unchanged, the bump in the LC disappears for the magnetar with smaller P i . We suggest that, once the SLSNe LCs with such kinds of bumps are observed, by fitting these LCs with our model, not only B d and P i of newly born magnetars but also the crucial physical quantitiesB t , R DU , and T c could be determined. Nonobservation of SLSNe LCs with such kinds of bumps hitherto may already put some (though very rough) constraints onB t , P i , R DU , and T c . Therefore, observation of SLSNe LCs may provide a new approach to probe the physics of newly born magnetars.PACS numbers:

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Section: Resultsmentioning

confidence: 99%

Probing the physics of newly born magnetars through observation of superluminous supernovae

Cheng

Zhang

et al. 2018

Phys. Rev. D

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“…Due to the high mass and high density of the ECM torus, the velocity of the FS relative to the unshocked torus cannot be much higher than the torus velocity, i.e., the escaping velocity. The timescale of the FS breaking out from the torus can be estimated by (Li & Yu 2016), which is shorter than t ev and t orb . Therefore, the energy accumulated by the FS is very limited.…”

Section: The Interaction Of a Pw With A Companionmentioning

confidence: 99%

“…Basically, PW emission could be mainly determined by the collisions of the PW with the AIC ejecta and, in 5 Due to the collision, a small amount of material can be stripped from the companion star, which is somewhat heated by a shock. Because of the high density of the companion, the shock velocity would not be much higher than the escaping velocity (Li & Yu 2016) and thus the heating effect may not be as effective as considered in Piro & Thompson (2014). particular, with the companion star.…”

Section: Introductionmentioning

confidence: 99%

X-Ray Transients from the Accretion-induced Collapse of White Dwarfs

Chen

2019

ApJL

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The accretion-induced collapse (AIC) of a white dwarf in a binary with a nondegenerate companion can sometimes lead to the formation of a rapidly rotating and highly magnetized neutron star (NS). The spin-down of this NS can drive a powerful pulsar wind (PW) and bring out some detectable multi-wavelength emissions. On the one hand, the PW can evaporate the companion in a few days to form a torus surrounding the NS. Then, due to the blockage of the PW by the torus, a reverse shock can be formed in the wind to generate intense hard X-rays. This emission component disappears in a few weeks' time, after the torus is broken down at its inner boundary and scoured into a very thin disk. On the other hand, the interaction between the PW with an AIC ejecta can lead to a termination shock of the wind, which can produce a long-lasting soft X-ray emission component. In any case, the high-energy emissions from deep inside the system can be detected only after the AIC ejecta becomes transparent for X-rays. Meanwhile, by absorbing the X-rays, the AIC ejecta can be heated effectively and generate a fast-evolving and luminous ultraviolet (UV)/optical transient. Therefore, the predicted hard and soft X-ray emissions, associated by an UV/optical transient, provide a clear observational signature for identifying AIC events in current and future observations (e.g., AT 2018cow).

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“…Besides contributing internal afterglow emission and energizing an SGRB external shock at the axial direction, the PW from a post-merger NS can also heat the nearly-isotropic merger ejecta with a high efficiency, because the merger ejecta is opaque at early times and can absorb the wind emission. Therefore, the thermal emission of the merger ejecta could be enhanced significantly Metzger & Piro 2014;Li & Yu 2016), while this emission was previously predicted to be mainly powered by the radioactive decays of r-process elements (Li & Paczyski 1998;Metzger et al 2010). Here the r-process elements can be efficiently synthesized in the merger ejecta because of the high neutron fraction.…”

Section: Short-duration Gamma-ray Bursts and Mergernovaementioning

confidence: 93%

“…The bolometric (dotted) and chromatic light curves of a mergernova emission driven by the spin-down of a post-merger NS(Li & Yu 2016). …”

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Studying newborn neutron stars by the transient emission after stellar collapses and compact binary mergers

Chen

Dai

et al. 2019

AIP Conference Proceedings

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The formation of neutron stars (NSs), both from collapses of massive stars and mergers of compact objects, can be usually indicated by bright transients emitted from explosively-ejected material. In particular, if the newborn NSs can rotate at a millisecond period and have a sufficiently high magnetic field, then the spin-down of the NSs would provide a remarkable amount of energy to the emitting material. As a result, super-luminous supernovae could be produced in the massive stellar collapse cases, while some unusual fast evolving and luminous optical transients could arise from the cases of NS mergers and accretion-induced collapses of white dwarfs. In all cases, if the dipolar magnetic fields of the newborn NSs can be amplified to be as high as 10 15 G, a relativistic jet could be launched and then a gamma-ray burst can be produced as the jet successfully breaks out from the surrounding nearly-isotropic ejected material. Neutron Stars and Transient PhenomenaFrom the pioneering work by Baade & Zwicky (1934), it has been widely considered that neutron stars (NSs) can be born from the core collapse of massive stars, accompanied by a luminous supernova emission. On the one hand, so far, thousands of NSs have been identified from our Galaxy through observations of pulsars, X-ray sources, etc. However, these Galactic NSs are generally older than a few thousand years. On the other hand, we can in principle explore newborn NSs by observing supernova emission and, meanwhile, thousands of supernovae have been detected from other galaxies beyond the Milky Way. Here, the problem is that the newborn NSs are always hid in a thick and dense supernova ejecta and usually have no impact on the supernova emission. The supernova emission is generally determined by the synthesization of nickels, the recombination of hydrogen and helium, and the interaction of the supernova ejecta with circum stellar medium (CSM). Therefore, in any case, our knowledge of NSs at their birth is actually very poor.Fortunately, this difficult situation might have being changed by the discovery of some unusual transient phenomena that are driven by the spin-down of a rapidly rotating and usually highly-magnetized NS. Such transient phenomena include super-luminous supernovae (SLSNe), gamma-ray bursts (GRBs), and mysterious fast evolving and luminous optical transients (FLTs). Therefore, it is definitely interesting and necessary to uncover how the newborn NSs can influence these transient emission and, simultaneously, to dig into the nature of these NSs by analyzing the transient observations. Super-luminous SupernovaeSLSNe are an unusual type of supernovae about 10 − 100 times brighter than the normal ones (Gal-Yam et al. 2012). If the total radiated energy of a typical SLSN of 10 51 erg is provided by radioactive decays of 56 Ni as usual, then the mass of the nickels should be about several to several tens of solar masses, which is nearly impossible for normal supernova

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Shock Breakout Driven by the Remnant of a Neutron Star Binary Merger: An X-Ray Precursor of Mergernova Emission

Cited by 30 publications

References 70 publications

Probing the physics of newly born magnetars through observation of superluminous supernovae

Probing the physics of newly born magnetars through observation of superluminous supernovae

X-Ray Transients from the Accretion-induced Collapse of White Dwarfs

Studying newborn neutron stars by the transient emission after stellar collapses and compact binary mergers

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