arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2211.04765astro-ph.SRastro-ph.EP
收藏

贝壳状恒星的磁场能捕获尘埃吗?

Can scallop-shell stars trap dust in their magnetic fields?

Hannah Sanderson, Moira Jardine, Andrew Collier Cameron, Julien Morin, Jean-Francois Donati

摘要:

开普勒和TESS任务中出现的一个难题是,在年轻的疏散星团和恒星形成区中,一小部分快速旋转的M矮星的光变曲线存在无法解释的下降。我们提出了一个可能的解释的理论调查-这是由尘埃云被困在恒星磁场。观测到的下沉的深度和持续时间使我们能够直接估计尘埃云的线性范围及其与旋转轴的距离。发现下降在0.4- 4.8%之间。我们发现,它们的距离是接近的共同旋转半径:典型的位置稳定点,带电粒子可以被困在恒星磁层。我们估计的电荷获得的尘埃粒子由于碰撞与日冕气体,从而确定的最大晶粒尺寸,可以磁支持,停止距离由于气体阻力和时间尺度上的尘埃粒子可以扩散出一个稳定的点。利用观测到的活动M矮星V374 Peg的磁场,我们模拟了这些尘埃云的分布,并产生了合成光变曲线。我们发现,对于1微米的尘埃颗粒,光变曲线有1% - 3%的下降,可以支持$10^{12}$ kg数量级的质量。我们的结论是,磁性捕获的尘埃云(可能来自残留的盘吸积或潮汐破坏的小行星或彗星体)能够解释开普勒和TESS数据中的周期性下降。

英文摘要:

One of the puzzles to have emerged from the Kepler and TESS missions is the existence of unexplained dips in the lightcurves of a small fraction of rapidly-rotating M dwarfs in young open clusters and star-forming regions. We present a theoretical investigation of one possible explanation - that these are caused by dust clouds trapped in the stellar magnetic fields. The depth and duration of the observed dips allow us to estimate directly the linear extent of the dust clouds and their distances from the rotation axis. The dips are found to be between 0.4-4.8%. We find that their distance is close to the co-rotation radius: the typical location for stable points where charged particles can be trapped in a stellar magnetosphere. We estimate the charge acquired by a dust particle due to collisions with the coronal gas and hence determine the maximum grain size that can be magnetically supported, the stopping distance due to gas drag and the timescale on which dust particles can diffuse out of a stable point. Using the observationally-derived magnetic field of the active M dwarf V374 Peg, we model the distribution of these dust clouds and produce synthetic light curves. We find that for 1 micron dust grains, the light curves have dips of 1% - 3% and can support masses of order of $10^{12}$kg. We conclude that magnetically-trapped dust clouds (potentially from residual disc accretion or tidally-disrupted planetesimal or cometary bodies) are capable of explaining the periodic dips in the Kepler and TESS data.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑