We show that the period clustering of anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), their X-ray luminosities, ages and statistics can be explained with fallback disks with large initial specific angular momentum. The disk evolution models are developed by comparison to self-similar analytical models. The initial disk mass and angular momentum set the viscous timescale. An efficient torque, with (1 - w^2) dependence on the fastness parameter w leads to period clustering in the observed AXP-SGR period range under a wide range of initial conditions. The timescale t_0 for the early evolution of the fallback disk, and the final stages of fallback disk evolution, when the disk becomes passive, are the crucial determinants of the evolution. The disk becomes passive at temperatures around 100 K, which provides a natural cutoff for the X-ray luminosity and defines the end of evolution in the observable AXP and SGR phase. This low value for the minimum temperature for active disk turbulence indicates that the fallback disks are active up to a large radius greater than ~10^{12} cm. We find that transient AXPs and SGRs are likely to be older than their persistent cousins. A fallback disk with mass transfer rates corresponding to the low quiescent X-ray luminosities of the transient sources in early evolutionary phases would have a relatively lower initial mass, such that the mass-flow rate in the disk is not sufficient for the inner disk to penetrate into the light cylinder of the young neutron star, making mass accretion onto the neutron star impossible. The transient AXP phase therefore must start later. The model results imply that the transient AXP/SGRs, although older, are likely to be similar in number to persistent sources (abridged).
For about half a century the radio pulsar population was observed to spin in the ~0.002-12s range, with different pulsar classes having a spin-period evolution that differs substantially depending on their magnetic fields or past accretion history. The recent detection of several slowly rotating pulsars has re-opened the long-standing question of the exact physics, and observational biases, driving the upper bound of the period range of the pulsar population. In this work, we perform a parameter study of the spin-period evolution of pulsars interacting with supernova fallback matter and specif…
We explore the impact of pulsar electromagnetic dipole and fallback accretion emission on the luminosity of a suite of kilonova models. The pulsar models are varied over pulsar magnetic field strength, pulsar lifetime, ejecta mass, and elemental abundances; the fallback models are varied over fallback accretion rate and ejecta mass. For the abundances, we use Fe and Nd as representatives of the wind and dynamical ejecta, respectively. We simulate radiative transfer in the ejecta in either 1D spherical or 2D cylindrical spatial geometry. For the grid of 1D simulations, the mass fraction of Nd i…
The central compact object 1E 161348$-$5055 in the supernova remnant RCW 103 has a spin period $\sim 6.67$ hr, making it the slowest isolated pulsar. It is believed that a supernova fallback disk is required to spin down the neutron star to the current spin period within a few $10^3$ yr. The mass of the fallback disk around newborn neutron stars can provide useful information on the supernova processes and the possible detection limit with optical/infrared observations. However, it is controversial how massive the disk is in the case of 1E 161348$-$5055. In this work we simulate the spin evolu…
The NuSTAR experiment detected a hard X-ray emission (10-70 keV) with a period of 8.68917 s and a pulse-phase modulation at 55 ks, or half this value, from the anomalous X-ray pulsar (AXP) 4U 0142+61. It is shown here that this evidence is naturally explained by the precession of a Keplerian supernova fallback disc surrounding this AXP. It is also found that the precession of discs formed around young neutron stars at distances larger than those considered in the past, may constitute almost neglected sources of gravitational waves with frequencies belonging to the sensitivity bands of the futu…
Recently, a 16-day periodicity in one fast radio burst is reported. We propose that this 16-day periodicity may be due to forced precession of the neutron star by a fallback disk. When the rotation axis is misaligned with the normal direction of the disk plane, the neutron star will precess. The eccentricity of the neutron star may be due to rotation or strong magnetic field etc. We found that the 16-day period may be understood using typical masses of the fallback disk. Polarization observations and information about the neutron star rotation period may help to discriminate different models. …
We explore the possibility that soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are powered by highly magnetized white dwarfs (B-WDs). We take a sample of SGRs and AXPs and provide the possible parameter space in mass, radius, and surface magnetic field based on their observed properties (period and its derivative) and the assumption that these sources obey the mass-radius relation derived for the B-WDs. The radius and magnetic field of B-WDs are adequate to explain energies in SGRs/AXPs as the rotationally powered energy. In addition, B-WDs also adequately explain the perpl…
The fallback disc model predicted that anomalous X-ray pulsars (AXPs) and soft-gamma repeaters (SGRs) will evolve to isolated long period pulsars before the discovery of the first two long-period pulsars (LPPs) this year. Unlike normal radio pulsars, LPPs show transient pulsed-radio epochs with unusual and variable pulse shapes, similar to the radio behaviour of the few radio emitting AXP/SGRs. We show that the present properties of the recently discovered second LPP, PSR J0901-4046 ($P \simeq 76$ s), are obtained as a result of evolution in interaction with a fallback disc, as we had already …
The detection of the unusually heavy binary neutron star merger GW190425 marked a stark contrast to the mass distribution from known Galactic pulsars in double neutron star binaries and gravitational-wave source GW170817. We suggest here a formation channel for heavy binary neutron stars and light black hole - neutron star binaries in which massive helium stars, which had their hydrogen envelope removed during a common envelope phase, remain compact and avoid mass transfer onto the neutron star companion, possibly avoiding pulsar recycling. We present three-dimensional simulations of the super…
Strong bursts from the anomalous X-ray pulsar 1E 1547.0-5408 observed with the INTEGRAL/SPI Anti-Coincidence Shield
2009年1月，不同的卫星从异常X射线脉冲星1 E 1547.0-5408的方向探测到多次短时间的软伽马射线爆发。在这里，我们报告的观测结果与INTEGRAL SPI-ACS探测器在最强的爆发活动期间。1月22日，在几个小时内探测到200多个能量超过80 keV的爆发。其中，两个非常明亮的事件显示出持续数秒的脉动尾部，并在1 E 1547.0-5408的2.1秒自旋周期进行调制。在这些爆发中，最亮的爆发释放的能量只有几个10^43尔格，假设距离为10千秒差距。这比从软伽马射线中继站观测到的三个巨型耀斑要小，但比从软伽马射线中继站和异常X射线中继站观测到的典型爆发要高。
Soft gamma repeaters (SGR) are identified as single neutron stars (NS) inside the Galaxy, or nearby galaxies, with sporadic transient gamma radiation. A total number of discovered SGR, including relative Anomalous X-ray pulsars (AXP), is few tens of objects. Many of them show periodic radiation, connected with NS rotation, with periods 2-12 s. The slow rotation is accompanied by small rate of loss of rotational energy, which is considerably smaller than the observed sporadic gamma ray luminosity, and is many orders less that the luminosity during giant bursts, observed in 4 SGR. Therefore the …
The Broad-band Noise Characteristics of Selected Anomalous X-Ray Pulsars and Soft Gamma-ray Repeaters
本文给出了2-60 keV能区反常X射线脉冲星（AXP）和软γ重复源（SGR）的宽带噪声结构。我们已经分析了罗西X射线定时探测器正比计数器阵列档案光曲线的四个AXP和一个SGR。我们检测到，这些源的持续发射显示在0.005-0.05 Hz的范围内的低频带限噪声变化从2.5%到70%的综合均方根时间的长时间的静止和以下爆发。我们在1 E 2259+586中发现了仅在2002年大爆发后$\sim$ 2年的限带红噪声。除此之外，系统没有显示出宽带噪声。虽然1 E 2259+586中的噪声上升发生在包括旋转毛刺的爆发之后，但其他毛刺AXP显示宽带噪声没有明显变化，因此该噪声似乎与毛刺无关。唯一显示出宽带噪声显著变化的源是1 E 1048.1-5937，其中噪声以每年$\sim$ 3.6%的速率逐渐上升1.95年。对于这个源的宽带噪声的增加是不相关的持续性和脉冲流量的大幅增加，或其两个短SGR样的爆发。这种噪声的上升确实是在一个长脉冲群之后开始的，但是考虑到该事件的稀疏性，以及类似脉冲群未被注意到的可能性，1 E 1048.1-5937中的噪声上升触发因素不像1 E 2259+586那样明确。其他三个源表明，相比之下，持续的低电平带限噪声。
The long-period ($P = 1091$ s) of the recently discovered pulsar GLEAM-X J162759.5-523504.3 can be attained by neutron stars evolving with fallback discs and magnetic dipole moments of a few $10^{30}$ G cm$^3$ at ages greater than $\sim 2 \times 10^5$ yr consistently with the observational upper limits to the period derivative, $\dot{P}$, and the X-ray luminosity, $L_X$, of the source. The current upper limits for $\dot{P}$ allow two alternative present states: (1) The disc is still active with ongoing accretion at a low rate such that the accretion luminosity is much less than the neutron sta…
Star quakes and internal phase transitions within anomalous x-ray pulsars (AXPs) and soft $γ$-ray repeaters (SGRs) can produce mini contractions and pulsar glitches. Shocks break out from their surface following such contractions produce thermal x/$γ$-ray bursts. Highly relativistic dipolar $e^+e^-$ bunches launched from the pulsar polar caps emit fast radio bursts (FRBs) of narrowly beamed coherent curvature radiation, visible if they point in the direction of Earth. Although these surface x/$γ$-ray bursts are isotropic and are many orders of magnitude more energetic than the FRBs, they are d…
Long-term spectral and timing properties of the soft gamma-ray repeater SGR 1833-0832 and detection of extended X-ray emission around the radio pulsar PSR B1830-08
The comparative analysis of parameters is carried out for two samples of radio pulsars. Objects of the first sample have periods P > 2 sec, the second is characterized by magnetic fields at the neutron star surface $Bs > 4.4\times10^{13}$ G. The main goal of this analysis is to find some differences between normal pulsars and anomalous X-ray pulsars (AXP) and soft gamma-ray repeaters (SGR) with the similar values of periods and magnetic fields. It is shown that the dependence of period derivatives on periods for pulsars with long periods is $dP/dt \propto P^{1.67}$. This means that we must sea…
AXPs and SGRs in the outer gap model: confronting Fermi observations
异常X射线源（AXP）和软伽马射线中继器（SGR）是磁星候选者，即，由强磁场提供能量的中子星。如果它们确实是磁星，它们将发射高能伽马射线，根据外隙模型，费米-LAT可以探测到。然而，没有显着的检测报告，在最近的费米-LAT观测所有已知的AXP和SGRs。考虑到理论与观测之间的差异，我们计算了所有AXP和SGR的理论谱，并给出了足够的观测参数。我们的结果表明，大多数AXP和SGR是高能γ射线发射体，如果他们真的是磁星。Fermi-LAT应检测到4个AXP 1 E 1547.0-5408、XTE J1810-197、1 E 1048.1-5937和4U 0142+61。在磁星的情况下，外能隙模型与费米观测之间存在矛盾。在磁星模型的可能解释进行了讨论。另一方面，如果AXP和SGR是回退磁盘系统，即，由于这些持续性辐射是由吸积提供动力的，因此它们中的大多数不是高能伽马射线发射体。未来对AXP和SGR的深Fermi-LAT观测将帮助我们弄清楚它们是磁星还是后备磁盘系统。
