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arXiv 1805.04547astro-ph.SR
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2013-2017年从空间和地面观测到的TW ~Hya从秒到年的光度变化

Photometric variability of TW~Hya from seconds to years as seen from space and the ground in 2013-2017

M. Siwak, W. Ogloza, A. F. J. Moffat, J. M. Matthews, S. M. Rucinski, T. Kallinger, R. Kuschnig, C. Cameron, W. W. Weiss, J. F. Rowe, D. B. Guenther, D. Sasselov

摘要:

这是基于MOST卫星观测的TW Hya的最后一次光度研究。在2014年和2017年期间,光变曲线分别显示出稳定的3.75和3.69 d准周期振荡。这两个值似乎都与恒星自转周期密切相关,因为它们可能是通过改变指向观测者的磁极附近形成的热点的可见度而产生的。这些主要的光变化叠加在由不稳定吸积产生的热点引起的混乱的耀斑型活动上-这种情况让人想起2011年,当时TW Hya显示出中等稳定吸积状态的迹象。在2015年,只观测到了漂移的准周期,与2008-2009年的数据相似,并且是在强烈不稳定状态下吸积的磁化恒星的典型特征。在2013-2017年期间获得了一组丰富的多色数据,其主要目的是表征TW Hya神秘掩星的基本光谱特性。虽然确定了几个可能的类似掩星的事件,但它们的定义不如2011年MOST数据中的定义明确。新的地面和MOST数据显示了十几个以前未被注意到的耀斑,以及与“吸积爆发”相关的小振幅,11分钟至3小时的亮度变化。不排除最短的11-15分钟的变化也可能是由吸积激波中的热不稳定振荡引起的。

英文摘要:

This is the final photometric study of TW Hya based on new MOST satellite observations. During 2014 and 2017 the light curves showed stable 3.75 and 3.69 d quasi-periodic oscillations, respectively. Both values appear to be closely related with the stellar rotation period, as they might be created by changing visibility of a hot-spot formed near the magnetic pole directed towards the observer. These major light variations were superimposed on a chaotic, flaring-type activity caused by hot-spots resulting from unstable accretion - a situation reminiscent of that in 2011, when TW Hya showed signs of a moderately stable accretion state. In 2015 only drifting quasi-periods were observed, similar to those present in 2008-2009 data and typical for magnetised stars accreting in a strongly unstable regime. A rich set of multi-colour data was obtained during 2013-2017 with the primary aim to characterize the basic spectral properties of the mysterious occultations in TW Hya. Although several possible occultation-like events were identified, they are not as well defined as in the 2011 MOST data. The new ground-based and MOST data show a dozen previously unnoticed flares, as well as small-amplitude, 11 min - 3 hr brightness variations, associated with 'accretion bursts'. It is not excluded that the shortest 11-15 min variations could also be caused by thermal instability oscillations in an accretion shock.

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。

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