标题： 来自裸奇异星的电磁信号 显示英文标题

标题： Electromagnetic signals from bare strange stars

摘要： 晶体色超导相被认为是在奇夸克质量足够大的情况下，禁闭夸克物质的基态。 该相具有比任何已知材料都更坚硬的显著特性。 因此，它可以承受大的剪切应力，支持大振幅的扭转振荡。 如果奇异星具有晶体色超导外壳，那么扭转振荡可能导致可观察到的电磁信号。 确实，考虑到一个简单的奇异星模型，其裸露的夸克物质表面，结果表明正电荷被局域在一个约十费米厚的狭窄壳层下。 用于中和夸克正电荷的电子会溢出到恒星外部，形成数百费米厚的电磁束缚大气层。 当激发扭转振荡时，例如通过恒星跳变，对于厚度为$1$千米的外壳，正电荷以典型的千赫兹频率振荡，而对于厚度为$9$千米的外壳，振荡频率可降至几百赫兹。 如果恒星外壳的厚度约为几厘米，可以达到几千赫兹的高频。 我们考虑了由振荡磁偶极子发射的情况，估计其发射功率可能相当大，约为$10^{51}$erg/s。 相关的弛豫时间非常不确定，对于厚度为$1$千米的外壳，弛豫时间在毫秒量级，而对于厚度为$9$千米的外壳，弛豫时间可达分钟量级。 辐射的光子部分会被电子大气层吸收，但其中相当一部分应该会从恒星发出。 显示英文摘要

摘要： The crystalline color superconducting phase is believed to be the ground state of deconfined quark matter for sufficiently large values of the strange quark mass. This phase has the remarkable property of being more rigid than any known material. It can therefore sustain large shear stresses, supporting torsional oscillations of large amplitude. The torsional oscillations could lead to observable electromagnetic signals if strange stars have a crystalline color superconducting crust. Indeed, considering a simple model of strange star with a bare quark matter surface, it turns out that a positive charge is localized in a narrow shell about ten Fermi thick beneath the star surface. The electrons needed to neutralize the positive charge of quarks spill in the star exterior forming an electromagnetically bounded atmosphere hundreds of Fermi thick. When a torsional oscillation is excited, for example by a stellar glitch, the positive charge oscillates with typical kHz frequencies, for a $1$ km thick crust, to hundreds of Hz, for a $9$ km thick crust. Higher frequencies, of the order of few GHz, can be reached if the star crust is of the order of few centimeters thick. We estimate the emitted power considering emission by an oscillating magnetic dipole, finding that it can be quite large, of the order of $10^{51}$ erg/s. The associated relaxation times are very uncertain, with values ranging between milliseconds, for a $1$ km thick crust, to minutes, for a $9$ km crust. The radiated photons will be in part absorbed by the electronic atmosphere, but a sizable fraction of them should be emitted by the star.