重评双简并LP400-22

The Way To a Double Degenerate: $\sim15-20$ per cent of $1M_{\odot} \le M \le 8M_{\odot}$ Stars have a $M>1M_{\odot}$ Companion

We find that $\sim 15-20$ per cent of A-type stars or red giants are bound with a massive companion ($M_{\rm secondary} > 1M_{\odot}$) in an intermediate wide orbit ($0.5<P<5000\mbox{ yr}$). These massive binaries are expected to form wide-orbit, double-degenerate systems (WODDs) within $\lesssim10\mbox{ Gyr}$ implying that $\sim10$ per cent of white dwarfs (WDs) are expected to be part of a WODD with a lighter WD companion. These findings are based on an analysis of previous adaptive optics observations of A-type stars and radial velocity measurements of red giants and shed light on the claim…

The double-degenerate, super-Chandrasekhar nucleus of the planetary nebula Henize 2-428

The planetary nebula (PN) stage is the ultimate fate of stars with mass 1 to 8 solar masses (M$_\odot$). The origin of their complex morphologies is poorly understood, although several mechanisms involving binary interaction have been proposed. In close binary systems, the orbital separation is short enough for the primary star to overfill its Roche lobe as it expands during the Asymptotic Giant Branch (AGB) phase. The excess material ends up forming a common-envelope (CE) surrounding both stars. Drag forces would then result in the envelope being ejected into a bipolar PN whose equator is coi…

作为超软X射线源的双简并Ia型超新星前身星--用SeBa进行的布居合成分析

On double-degenerate type Ia supernova progenitors as supersoft X-ray sources - A population synthesis analysis using SeBa

背景：Ia型超新星（SN）祖先的性质仍然不清楚。虽然通常认为单简并祖系统将是发光的超软X射线源（SSS），但最近提出双简并祖系统也可能经历SSS阶段。目的：我们的目标是研究双退化祖系统SSSs的可能性，并将严格的上限上的最大可能的持续时间的任何SSS阶段和预期数量的这些系统在银河系人口。方法：我们采用二进制人口合成代码SeBa检查的质量传递特性的一个可能的SSS阶段的双退化Ia型SN祖系统1）标准SeBa的假设，和2）一个乐观的最佳情况下的情况。后一种情况建立了严格的上限的超软源双退化Ia型SN祖系统的可能人口。结果如下：我们的研究结果表明，不同于预期的单简并祖系统，绝大多数的材料吸积的纯风质量转移或风和RLOF质量转移的组合是氦，而不是氢。即使对质量传递和保留效率有非常乐观的假设，最终成为双简并Ia型SNe的系统所吸积的平均质量也很小。因此，即使在最佳条件下，这些系统成为SSS的时间也很短，而且银河系中此类系统的预期数量可以忽略不计。结论：作为SSS的双简并Ia型SN祖先的数量至少比预期为SSS的单简并祖先的数量小一个数量级，并且双简并系统的超软X射线行为通常在SN爆炸之前很久就停止了。

恒星形成历史对薄盘中近双星简并引力波信号的影响

The influence of star formation history on the gravitational wave signal from close double degenerates in the thin disc

利用蒙特卡罗模拟计算了薄银盘中双简并体（DDs）产生的预期引力波（GW）信号。年轻的关闭DD的数量，将有助于可观察的离散信号的频率范围$1.58 - 15.8$兆赫估计与建议GW观测站的灵敏度比较。目前的DD人口检查作为银河系恒星形成历史的函数。它表明，频率分布，特别是，是一个敏感的函数的银河系恒星形成的历史，并可以用来衡量的时间，因为最后一个主要的恒星形成时代。

双简并星并合的引人入胜的结果

The intriguing outcomes of double degenerate mergers

本综述探讨白矮星并合的多种结果，指出并非所有双简并星并合都产生超新星，可能形成更重白矮星、部分爆炸残骸或坍缩为中子星/磁星，并可能作为长伽马射线暴和快速射电暴的前身。

The Gravitational Wave Emission of Double White Dwarf Coalescences

Type Ia Supernovae (SNe Ia) are widely used as standard candles to probe the Universe. However, how these fierce explosions are produced itself is still a highly debated issue. There are mainly two popular models for SNe Ia, i.e. the double-degenerate scenario and the single-degenerate scenario. The double-degenerate scenario suggests that SNe Ia are produced by the coalescence of two degenerate white dwarfs, while the single-degenerate scenario suggests that the continuous accretion of a single degenerate white dwarf from its normal stellar companion will finally lead to a disastrous explosio…

Future prospects for ground-based gravitational wave detectors $-$ The Galactic double neutron star merger rate revisited

We present the Galactic merger rate for double neutron star (DNS) binaries using the observed sample of eight DNS systems merging within a Hubble time. This sample includes the recently discovered, highly relativistic DNS systems J1757$-$1854 and J1946+2052, and is approximately three times the sample size used in previous estimates of the Galactic merger rate by Kim et al. Using this sample, we calculate the vertical scale height for DNS systems in the Galaxy to be $z_0 = 0.4 \pm 0.1$ kpc. We calculate a Galactic DNS merger rate of $\mathcal{R}_{\rm MW} = 42^{+30}_{-14}$ Myr$^{-1}$ at the 90%…

用LISA检测Ia型SNe双简并祖细胞

Detecting Double Degenerate Progenitors of SNe Ia with LISA

银河系的白矮星双星有望为激光干涉仪空间天线（LISA）等低频探测器提供最多的引力波源。目前的数据分析技术已经证明了从两年的观测中分辨出$10^4$白矮星双星的能力。分辨出的二进制要么是高频率的，要么是大振幅的。这样的系统更有可能是高质量的双星，其中的一个子集将是超新星Ia在双简并情况下的祖先。我们报告的研究结果的解决二进制使用人口合成模型的银河系白矮星二进制和LISA数据分析算法使用模拟LISA数据挑战工具的属性。

3D Hydrodynamical Simulations of Helium-Ignited Double-degenerate White Dwarf Mergers

The origins of type Ia supernovae (SNe Ia) are still debated. Some of the leading scenarios involve a double detonation in double white dwarf (WD) systems. In these scenarios, helium shell detonation occurs on top of a carbon-oxygen (CO) WD, which then drives the detonation of the CO-core, producing a SN Ia. Extensive studies have been done on the possibility of a double helium detonation, following a dynamical helium mass-transfer phase onto a CO-WD. However, 3D self-consistent modeling of the double-WD system, the mass transfer, and the helium shell detonation have been little studied. Here …

Sub-Chandrasekhar-mass white dwarf detonations revisited

The detonation of a sub-Chandrasekhar-mass white dwarf (WD) has emerged as one of the most promising Type Ia supernova (SN Ia) progenitor scenarios. Recent studies have suggested that the rapid transfer of a very small amount of helium from one WD to another is sufficient to ignite a helium shell detonation that subsequently triggers a carbon core detonation, yielding a "dynamically-driven double degenerate double detonation" SN Ia. Because the helium shell that surrounds the core explosion is so minimal, this scenario approaches the limiting case of a bare C/O WD detonation. Motivated by disc…

Double neutron stars: merger rates revisited

We revisit double neutron star (DNS) formation in the classical binary evolution scenario in light of the recent LIGO/Virgo DNS detection (GW170817). The observationally estimated Galactic DNS merger rate of $R_{\rm MW}=21^{+28}_{-14}$ Myr$^{-1}$, based on 3 Galactic DNS systems, fully supports our standard input physics model with $R_{\rm MW} =24$ Myr$^{-1}$. This estimate for the Galaxy translates in a non-trivial way (due to cosmological evolution of progenitor stars in chemically evolving Universe) into a local ($z\approx0$) DNS merger rate density of $R_{\rm local}=48$ Gpc$^{-3}$yr$^{-1}$…