Magnetic Wind From a Massive White Dwarf Merger: Summary and Discussion
by Magnetosphere: Maintaining Habitability on EarthMay 15th, 2024
Too Long; Didn't Read
This paper explores the observation properties of massive white dwarf merger remnants with a strong magnetic field, a fast spin, and intense mass loss.
This paper is available on arxiv under CC 4.0 license.
Authors:
(1) Yici Zhong, Department of Physics, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan;
(2) Kazumi Kashiyama, Research Center for the Early Universe, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan and Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU,WPI), The University of Tokyo, Chiba 277-8582, Japan;
(3) Shinsuke Takasao, Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan;
(4) Toshikazu Shigeyama, Research Center for the Early Universe (RESCEU), School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan and Department of Astronomy, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan;
(5) Kotaro Fujisawa, Research Center for the Early Universe (RESCEU), School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan and Department of Liberal Arts, Tokyo University of Technology, Ota-ku, Tokyo 144-0051, Japan.
Table of Links
Appendix
C. Change of the Mass Loss Rate in MHD Regime
4. SUMMARY AND DISCUSSION
Hence, even if the currently observed wind of WD J005311 is a rotating magnetic one and continues to blow for a Kelvin-Helmholtz timescale of the central WD, which is ∼ 1, 000-10, 000, yr, the spin-down will be negligible. When the carbon burning in the near-surface region ceases, the mass loss rate will significantly decrease, which increases the dimensionless parameter σ. The rotating magnetic wind will then become relativistic and eventually enter the force-free regime without significantly spinning down the WD. In this case, the remnant WD may serve as a non-thermal radiation source, or or the so-called WD pulsar (e.g., Kashiyama et al. 2011).
Finally, we address some caveats in our numerical simulations. We have implemented a simple prescription for the near-surface carbon burning region as source terms (Eqs. 13 and 14), referred to as the wind launching region. However, the actual near-surface carbon burning region should be convective, and can be affected by the strong magnetic field. The structure of the convective region, the resulting wind launch, and its chemical composition would also be influenced by the radiative transfer. For accurate multi-wavelength spectrum calculations, it is desirable to conduct a comprehensive radiative MHD simulation that covers from the carbon burning layer to the photosphere radius. Also, we only investigate the aligned rotating dipole magnetic fields in this paper, while a more complicated field configuration such as oblique or off-centered dipole may be realized for the remnant WD system. Finally, the deformation of the central WD due to its rapid rotation and anisotropic carbon burning can alter the observed properties as well. We save the investigations into the above topics for our future work.
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