We investigate the direct contribution of the magnetic field to the gravitational wave generation. To do so, we study the post-Newtonian energy-momentum tensor of the magnetized fluid and the post-Newtonian expansion of the gravitational potential in the wave zone. We show that the magnetic field appears even in the first post-Newtonian order of the multipole moment tensor. Then, we find an explicit relativistic correction containing the magnetic field contribution to the well-known quadrupole formula. As an application of this derivation, we find that the B-field part of the gravitational waves released in the early stages of a millisecond magnetar's life can be as much as one-hundredth of the signals due to the deformed rotating neutron stars. We show that although the event rate of this system is small, the signal would lie in the sensitivity range of the next generation of detectors.
The spin-down energy of millisecond magnetars has been invoked to explain X-ray afterglow observations of a significant fraction of short and long gamma-ray bursts. Here, we extend models previously introduced in the literature, incorporating radiative losses with the spin down of a magnetar central engine through an arbitrary braking index. Combining this with a model for the tail of the prompt emission, we show that our model can better explain the data than millisecond-magnetar models without radiative losses or those that invoke spin down solely through vacuum dipole radiation. We find tha…
Two classes of X-ray/$γ$-ray sources, the Soft Gamma Repeaters and the Anomalous X-ray Pulsars have been identified with isolated, slowly spinning magnetars, neutron stars whose emission draws energy from their extremely strong magnetic field ($\sim 10^{15}-10^{16}$ G). Magnetars are believed to form with millisecond spin period and to represent an important fraction of the whole population of young neutron stars. Newborn magnetars can convert very quickly their rotational energy into electromagnetic and/or gravitational waves, by virtue of their strong magnetic fields and fast spins. This cha…
Reverse Shock Emission Driven By Post-Merger Millisecond Magnetar Winds: Effects of the Magnetization Parameter
对短持续时间伽马射线暴的研究提供了越来越多的证据，证明很大一部分双中子星合并导致了稳定的毫秒磁星的形成。毫秒磁星发射的坡印廷通量可以留下独特的电磁特征，揭示磁星风中的能量耗散过程。在以前的研究中（Wang & Dai 2013 b; Wang et al. 2015），我们假设磁星风完全由轻子主导，因此磁星风中的电子/正电子被扩散激波加速。然而，对脉冲星风星云的理论模拟表明，在许多情况下，脉冲星风中的磁场能量可能足够强，足以抑制扩散激波加速。本文研究了磁星风在任意磁化参数$σ$下的反向激波发射和正向激波发射。我们发现，反向冲击辐射强烈地依赖于$σ$，特别是，$σ\sim 0.3$导致最强的反向冲击辐射。未来的观测将有助于诊断磁星风的组成。
Magnetic-distortion-induced ellipticity and gravitational wave radiation of neutron stars: millisecond magnetars in short GRBs, Galactic pulsars, and magnetars
中子星由于磁畸变而可能产生非轴对称形变，是地基干涉测量探测器的连续引力波（GW）源。经过几十年的搜索，使用现有的GW探测器，没有证据表明GW信号来自任何脉冲星。椭圆率的上限越来越严格地限制在银河系的恒星上。在这项工作中，我们使用的椭圆率推断从假定的毫秒磁星在短伽马射线暴（SGRB），以估计其可探测性目前和未来的GW探测器。对于从SGRB数据推断的$\sim 1$ ms磁星，高级LIGO（aLIGO）和爱因斯坦望远镜（ET）的探测视界分别为$\sim 30$ Mpc和$\sim 600$ Mpc。利用SGRB毫秒磁星的椭圆率作为刻度，在假设椭圆率是磁畸变引起的情况下，我们估算了银河系中的毫秒磁星和磁星的椭圆率和引力波应变。我们发现，该结果与aLIGO O 1对银河系恒星和磁星的零探测结果是一致的。我们进一步预测，GW信号从这些恒星/磁星可能无法检测到目前设计的aLIGO探测器。ET检测器可能能够检测来自这些天线中的一些天线的一些相对低频的信号（$<50$ Hz）。受其设计灵敏度的限制，eLISA探测器似乎不适合探测来自银河系恒星和磁星的信号。
Millisecond magnetars are often invoked as the central engine of some gamma-ray bursts (GRBs), specifically the ones showing a plateau phase. We argue that an apparent plateau phase may not be realized if the magnetic field of the nascent magnetar is in a transient rapid decay stage. Some GRBs that lack a clear plateau phase may also be hosting millisecond magnetars. We present an approximate analytical solution of the coupled set of equations describing the evolution of the angular velocity and the inclination angle between rotation and magnetic axis of a neutron star in the presence of a co-…
Relativistic jets from millisecond proto-magnetars
University of Greifswald（格赖夫斯瓦尔德大学）；Perimeter Institute for Theoretical Physics（基础物理研究所）；University of Guelph（圭尔夫大学）；Columbia University（哥伦比亚大学）；Flatiron Institute（平顿研究所）
In this paper, we revisit the scenario that an internal gradual magnetic dissipation takes place within the wind from a newborn millisecond magnetar can be responsible for gamma-ray burst production. We show that a combination of two emission components in this model, i.e., the photospheric emission from the wind and the synchrotron radiation within the magnetic reconnection region, can give a reasonable fit to the observed spectrum of the prompt emission phase of GRB 160804A. We obtain the physical parameters through a Monte Carlo procedure and deduce the initial spin period and magnetic fiel…
The afterglow emission of some gamma-ray bursts (GRBs) show a shallow decay (plateau) phase implying continuous injection of energy. The source of this energy is very commonly attributed to the spin-down power of a nascent millisecond magnetar. The magnetic dipole radiation torque is considered to be the mechanism causing the spin-down of the neutron star. This torque has a component working for the alignment of the angle between rotation and magnetic axis, i.e., inclination angle, which has been neglected in modelling GRB afterglow light curves. Here, we demonstrate the evolution of the incli…
Two accretion columns have been argued to form over the surface of a newborn millisecond magnetar for an extremely high accretion rate $\gtrsim1.8\times10^{-2}M_\odot\ {\rm s^{-1}}$ that may occur in the core-collapse of a massive star. In this paper, we investigate the characteristics of these accretion columns and their gravitational wave (GW) radiation. For a typical millisecond magnetar (surface magnetic field strength $B\sim10^{15}$ G and initial spin period $P\sim1$ ms), we find (1) its accretion columns are cooled via neutrinos and can reach a height $\sim1$ km over the stellar surface;…
The origin of the X-ray afterglows of gamma-ray bursts has regularly been debated. We fit both the fireball-shock and millisecond-magnetar models of gamma-ray bursts to the X-ray data of GRB 130603B and 140903A. We use Bayesian model selection to answer the question of which model best explains the data. This is dependent on the maximum allowed non-rotating neutron star mass $M_{\textrm{TOV}}$, which depends solely on the unknown nuclear equation of state. We show that the data for GRB140903A favours the millisecond-magnetar model for all possible equations of state, while the data for GRB1306…
In this paper we study the spin-evolution and gravitational-wave luminosity of a newly born millisecond magnetar, formed either after the collapse of a massive star or after the merger of two neutron stars. In both cases we consider the effect of fallback accretion, and consider the evolution of the system due to the different torques acting on the star, namely the spin up torque due to accretion and spin-down torques due to magnetic dipole radiation, neutrino emission, and gravitational wave emission linked to the formation of a `mountain' on the accretion poles. Initially the spin period is …
Ejector and propeller spin-down: How might a superluminous supernova millisecond magnetar become the 6.67 hr pulsar in RCW103
超新星遗迹RCW 103中的X射线源1 E 161348-5055最近表现出磁星的典型X射线活动，即磁场> 10 ^14 - 10 ^15 G的中子星。然而，1 E 161348-5055的观测周期为6.67小时，而磁星的自旋周期为秒。在这里，我们描述了一个简单的模型，它可以解释1 E 161348-5055的自旋演化，以及其他磁星，从一个初始的毫秒，将需要发电机产生的磁场强度磁场。我们认为，1 E 161348-5055与其他磁星的关键区别在于其残留盘的总质量较小。这个圆盘导致1 E 161348-5055在其生命中经历了喷射器和螺旋桨阶段，在此期间，强大的扭矩导致其自旋周期迅速增加。通过匹配观测到的自旋周期和1-3 kyr的年龄，我们发现1 E 161348-5055在所有已知的磁星中具有（略）最高的磁场，B~ 5 × 10^15 G，其盘的质量约为10^24 g，与小行星谷神星相当。
The binary neutron star merger GW170817/GRB170817A confirmed that at least some neutron star mergers are the progenitors of short gamma-ray bursts. Many short gamma-ray bursts have long-term x-ray afterglows that have been interpreted in terms of post-merger millisecond magnetars---rapidly rotating, highly magnetised, massive neutron stars. We review our current understanding of millisecond magnetars born in short gamma-ray bursts, focusing particularly three main topics. First, whether millisecond magnetars really do provide the most plausible explain for the x-ray plateau. Second, determinin…
Probing millisecond magnetar formation in binary neutron star mergers through X-ray follow-up of gravitational wave alerts
Université Paris-Saclay（巴黎萨克雷大学）；Université Paris Cité（巴黎西岱大学）；CEA（法国原子能和替代能源委员会）；CNRS（法国国家科学研究中心）；Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））；CNRS/IN2P3, IJCLab（法国国家科学研究中心/法国国家核物理与粒子物理研究所，IJCLab实验室）；Institut d’Astrophysique de Paris（巴黎天文物理研究所）；Sorbonne Université（索邦大学）；Università di Torino（都灵大学）
Comparison of gravitational waves from central engines of gamma-ray bursts: neutrino-dominated accretion flows, Blandford-Znajek mechanisms, and millisecond magnetars
Some neutron stars may be born spinning fast and with strong magnetic fields---the so-called \emph{millisecond magnetars}. It is important to understand how a star's magnetic axis moves with respect to the spin axis in the star's early life, as this effects both electromagnetic and gravitational wave emission. Previous studies have highlighted the importance of viscous dissipation within the star in this process. We advance this program by additionally considering the effect of the electromagnetic torque. We find an interesting interplay between the viscous dissipation, which makes the magneti…
In the last 25 years, a new generation of X-ray satellites imparted a significant leap forward in our knowledge of X-ray pulsars. The discovery of accreting and transitional millisecond pulsars proved that disk accretion can spin up a neutron star to a very high rotation speed. The detection of MeV-GeV pulsed emission from a few hundreds of rotation-powered pulsars probed particle acceleration in the outer magnetosphere, or even beyond. Also, a population of two dozens of magnetars has emerged. INTEGRAL played a central role to achieve these results by providing instruments with high temporal …
A rapidly rotating and highly magnetized neutron star (NS) could be formed from the explosive phenomena such as superluminous supernovae and gamma-ray bursts. This newborn NS can substantially influence the emission of these explosive transients through its spin-down. The spin-down evolution of the NS can sometimes be affected by fallback accretion, although it is usually regulated by the magnetic dipole radiation and gravitational wave radiation of the NS. Under appropriate conditions, the accreting material can be firstly ejected and subsequently recycled back, so that the accretion disk can…
Magnetars are highly magnetized young neutron stars that occasionally produce enormous bursts and flares of X-rays and gamma-rays. Of the approximately thirty magnetars currently known in our Galaxy and Magellanic Clouds, five have exhibited transient radio pulsations. Fast radio bursts (FRBs) are millisecond-duration bursts of radio waves arriving from cosmological distances. Some have been seen to repeat. A leading model for repeating FRBs is that they are extragalactic magnetars, powered by their intense magnetic fields. However, a challenge to this model has been that FRBs must have radio …
Magnetars, a population of isolated neutron stars with ultra-strong magnetic fields of $\sim 10^{14}-10^{15}$ G, have been increasingly accepted to explain a variety of astrophysical transients. A nascent millisecond-period magnetar can release its spin-down energy and power bright sources such as Gamma-ray Bursts (GRBs) and their subsequent X-ray plateaus, Super Luminous Supernovae (SLSNe), and the fast X-ray transients such as CDF-S XT-2. Magnetars with ages of $10^3-10^4$ years have been observed within the Milky Way Galaxy, which are found to power diverse transients with the expense of th…
Since their discovery in 2007, much effort has been devoted to uncovering the sources of the extragalactic, millisecond-duration fast radio bursts (FRBs). A class of neutron star known as magnetars is a leading candidate source of FRBs. Magnetars have surface magnetic fields in excess of $10^{14}$ G, the decay of which powers a range of high-energy phenomena. Here we present the discovery of a millisecond-duration radio burst from the Galactic magnetar SGR 1935+2154, with a fluence of $1.5\pm 0.3$ Mega-Jansky milliseconds. This event, termed ST 200428A(=FRB 200428), was detected on 28 April 20…
Superluminous supernovae (SLSNe) are massive star explosions too luminous to be powered by traditional energy sources, such as radioactive 56Ni. These transients may instead be powered by a central engine, such as a millisecond pulsar or magnetar, whose relativistic wind inflates a nebula of high energy particles and radiation behind the expanding ejecta. We present 3D Monte Carlo radiative transfer calculations which follow the production and thermalization of high energy radiation from the nebula into optical radiation and, conversely, determine the gamma-ray emission that escapes the ejecta…
`Internal plateau' followed by a sharp decay is commonly seen in short gamma-ray burst (GRB) light curves. The plateau component is usually interpreted as the dipole emission from a supra-massive magnetar, and the sharp decay may imply the collapse of the magnetar to a black hole (BH). Fall-back accretion onto the new-born BH could produce long-lasting activities via the Blandford-Znajek (BZ) process. The magnetic flux accumulated near the BH would be confined by the accretion disks for a period of time. As the accretion rate decreases, the magnetic flux is strong enough to obstruct gas infall…
Energy Loss of Newborn Magnetars by Schwinger Process
Institute for Basic Science（基础科学研究所）；Gwangju Institute of Science and Technology（光州科学技术院）；Kunsan National University（群山国立大学）；ICRANet（国际相对论天体物理中心网络）；Sapienza Università di Roma（罗马智慧大学）；INAF（意大利国家天体物理研究所）
Extremely bright coherent radio bursts with millisecond duration, reminiscent of cosmological fast radio bursts (FRBs), were co-detected with anomalously-hard X-ray bursts from a Galactic magnetar SGR 1935$+$2154. We investigate the possibility that the event was triggered by the magnetic energy injection inside the magnetosphere, thereby producing magnetically-trapped fireball (FB) and relativistic outflows simultaneously. The thermal component of the X-ray burst is consistent with a trapped FB with an average temperature of $\sim200$-$300$ keV and size of $\sim10^5$ cm. Meanwhile, the non-th…
The radiation-loud and radiation-quiet anti-glitches in magnetar 1E 2259+586 are discussed together. It is shown that the 2019 radiation-quiet anti-glitch in 1E 2259+586 is not constraining, because its amplitude is 2.5 smaller than the previous radiation-loud anti-glitch. We note that magnetars with high X-ray luminosity and low rotational energy loss rate are more likely to show anti-glitches. Anti-glitchers and radio-emitters of magnetars occupy opposite corner on the luminosity vs. rotational energy loss rate diagram. By introducing the X-ray luminosity parameter and the activity parameter…
Weak and continuous gravitational-wave (GW) radiation can be produced by newborn magnetars with deformed structure and is expected to be detected by the Einstein telescope in the near future. In this work we assume that the deformed structure of a nascent magnetar is not caused by a single mechanism but by multiple time-varying quadrupole moments such as those present in magnetically induced deformation, starquake-induced ellipticity, and accretion column-induced deformation. The magnetar loses its angular momentum through accretion, magnetic dipole radiation, and GW radiation. Within this sce…
