arXiv 2109.061582021-09astro-ph.SRastro-ph.HEhep-ph

中微子发射率对白矮星内部磁场的探测

Neutrino Emissivities as a Probe of the Internal Magnetic Fields of White Dwarfs

Marco Drewes, Jamie McDonald, Loïc Sablon, Edoardo Vitagliano

备注：: 21 pages, 6 figures. Matches published version
发表信息：: Astrophys. J. 934, 99 (2022)
DOI：: 10.3847/1538-4357/ac7874

摘要：

白矮星（WD）的演化主要取决于热过程。它们核心的等离子体可以产生从恒星逃逸的中微子，从而导致能量损失。虽然在没有磁场的情况下，主要的冷却机制是高温下的等离子体衰变和低温下的光子表面发射，但是即使是普通WD，也隐藏在表面下方的芯中的大磁场，并且分光偏振测量无法检测到，可能会在冷却中留下印记。在本文中，我们重新审视的贡献WD冷却源于中微子对同步辐射和磁场对等离子体衰变的影响。我们的关键发现是，即使观测限制了恒星表面的磁场强度，WD内部的磁场-无论是否有表面磁场-都可以强大到足以修改冷却速率，中微子对同步辐射是最重要的贡献。这种效应可能不仅与冷却异常的量化和解释相关，而且还表明WD的内部磁场应小于$\sim 6\times 10^{11}\,\rm G$，略微改善了来自稳定性要求的边界。虽然我们的WD结构的简化处理意味着需要进一步的研究，以减少系统的不确定性，比较的发射率的基础上的估计说明了潜在的中微子发射作为诊断工具，研究内部的WD。

英文摘要：

The evolution of white dwarfs (WDs) depends crucially on thermal processes. The plasma in their core can produce neutrinos which escape from the star, thus contributing to the energy loss. While in absence of a magnetic field the main cooling mechanism is plasmon decay at high temperature and photon surface emission at low temperature, a large magnetic field in the core hiding beneath the surface even of ordinary WDs, and undetectable to spectropolarimetric measurements, can potentially leave an imprint in the cooling. In this paper, we revisit the contribution to WD cooling stemming from neutrino pair synchrotron radiation and the effects of the magnetic field on plasmon decay. Our key finding is that even if observations limit the magnetic field strength at the stellar surface, magnetic fields in the interior of WDs -- with or without a surface magnetic field -- can be strong enough to modify the cooling rate, with neutrino pair synchrotron emission being the most important contribution. This effect may not only be relevant for the quantification and interpretation of cooling anomalies, but also suggests that the internal magnetic fields of WDs should be smaller than $\sim 6\times 10^{11}\,\rm G$, slightly improving bounds coming from a stability requirement. While our simplified treatment of the WD structure implies that further studies are needed to reduce the systematic uncertainties, the estimates based on comparing the emissivities illustrate the potential of neutrino emission as a diagnostic tool to study the interior of WDs.

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