We introduce a classification scheme of the post-merger dynamics and gravitational-wave emission in binary neutron star mergers, after identifying a new mechanism by which a secondary peak in the gravitational-wave spectrum is produced. It is caused by a spiral deformation, the pattern of which rotates slower with respect to the double-core structure in center of the remnant. This secondary peak is typically well separated in frequency from the secondary peak produced by a nonlinear interaction between a quadrupole and a quasi-radial oscillation. The new mechanism allows for an explanation of low-frequency modulations seen in a number of physical characteristics of the remnant, such as the central lapse function, the maximum density and the separation between the two cores. We find empirical relations for both types of secondary peaks between their gravitational-wave frequency and the compactness of nonrotating individual neutron stars, that exist for fixed total binary masses. These findings are derived for equal-mass binaries without intrinsic neutron-star spin analyzing hydrodynamical simulations without magnetic field effects. Our classification scheme may form the basis for the construction of detailed gravitational-wave templates of the post-merger phase. We find that the quasi-radial oscillation frequency of the remnant decreases with the total binary mass. For a given merger event our classification scheme may allow to determine the proximity of the measured total binary mass to the threshold mass for prompt black hole formation, which can, in turn, yield an estimate of the maximum neutron-star mass.
Reproducing the observed abundances in RCB and HdC stars with post-double degenerate merger models - constraints on merger and post-merger simulations and physics processes
The Post-Merger Magnetized Evolution of White Dwarf Binaries: The Double-Degenerate Channel of Sub-Chandrasekhar Type Ia Supernovae and the Formation of Magnetized White Dwarfs
Pulsations driven by the $ε$-mechanism in post-merger remnants: first results
富氦次矮星是热次矮星中一个罕见的子类，它们组成了一个小而不均匀的群体，显示出不同程度的氦富集。只有一颗恒星LS IV $^\circ$ 14 116被发现显示出多周期的光度变化。LS IV $^\circ$ 14 116的变异性已经被解释为非径向g模式振荡的结果，其激发在标准$κ$机制驱动sdBV恒星脉动的框架内是难以理解的。在最近的一项研究中，我们提出，LS IV $^\circ$ 14 116的脉动可能是通过$ε$ -机制作用于恒星内部不稳定的氦燃烧区，出现在静止的氦燃烧阶段之前。少数几个被接受的富氦次矮星形成的场景之一是两个氦核白矮星的合并。作为该项目的一部分，我们提出了一个研究的$ε$机制合并后的残余物，并讨论了结果的光LS IV $^\circ$ 14 116所表现出的脉动。
Post-merger rotational evolution of magnetised single hot subdwarfs results in slow rotation due to magnetic braking
Instituto de Astrofísica de La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)（拉普拉塔天文物理研究所）；Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata (UNLP)（拉普拉塔国立大学天文与地球物理学院）；Heidelberger Institut für Theoretische Studien (HITS)（海德堡理论研究所）；London Centre for Stellar Astrophysics（伦敦恒星天体物理学中心）
