Unified Model of Outbursts in Dwarf Novae

矮新星爆发的统一模型

基本信息

批准号：
04640267
负责人：
OSAKI Yoji
金额：
$ 1.41万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04640267/
关键词：
Cataclysmic Variables Accretion Disk Dwarf Novae SU Ursa Majoris Stars WZ Sagittae Stars Stability Superoutburst 流体シミュレーション固有振動モード

项目摘要

Dwarf novae are eruptive variables showing repetitive outbursts of amplitudes of 2-6 magnitude. There are three sub-classes in dwarf novae : the U Gem-type showing only the ordinary outbursts, the Z Cam-type showing occasional standstill, and the SU UMa-type showing superoutbursts. The main purpose of this research is to examine whether or not we can explain rich variety of outburst phenomena in dwarf novae by a unified paradigm : the so-called disk instability model. To this end, we have made detailed numerical simulations of the superoutburst phenomenon of SU UMa stars by the combined mechanism of the thermal and tidal instabilities of accretion disks. It has been found that the superoutburst cycle of SU UMa stars can be successfully reproduced by this model. We have formulated the tidal eccentric instability of an accretion disk as an eigenvalue problem of the oscillation of the one-armed mode in the accretion disk and we have examined the eigenvalue and eigenfunction of this mode both numerically and analytically. The disk instability model for SU UMa-type dwarf novae is examined in relation to the WZ Sge-type dwarf novae which exhibit only superoutbursts but apparently no normal outburst. A particular case of the most extreme star of WZ Sge itself is discussed and it is suggested as an extreme case of very low viscosity in quiescence and of rather low mass transfer rate from the secondary.

矮新星是爆发性变量，显示出 2-6 级振幅的重复爆发。矮新星分为三个子类：仅显示普通爆发的 U Gem 型、显示偶尔静止的 Z Cam 型和显示超级爆发的 SU UMa 型。这项研究的主要目的是检验我们是否可以通过一个统一的范式来解释矮新星中丰富多样的爆发现象：所谓的盘不稳定模型。为此，我们利用吸积盘热不稳定性和潮汐不稳定性的组合机制对SU UMa星的超爆发现象进行了详细的数值模拟。研究发现，该模型可以成功再现SU UMa星的超爆发周期。我们将吸积盘的潮汐偏心不稳定性表述为吸积盘中单臂模态振荡的特征值问题，并从数值和解析方面研究了该模态的特征值和特征函数。 SU UMa 型矮新星的盘不稳定性模型与 WZ Sge 型矮新星的关系进行了检验，WZ Sge 型矮新星仅表现出超级爆发，但显然没有正常爆发。讨论了 WZ Sge 本身最极端的恒星的一个特殊情况，并建议将其视为静止时粘度非常低和来自次级的传质率相当低的极端情况。