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arXiv 0905.0120astro-ph.SRastro-ph.IM
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共生星天鹅座CH中非径向脉动和微弱伴星的探测

Detection of non-radial pulsation and faint companion in the symbiotic star CH Cyg

E. Pedretti, J. D. Monnier, S. Lacour, W. A. Traub, W. C. Danchi, P. G. Tuthill, N. D. Thureau, R. Millan-Gabet, J-P. Berger, M. G. Lacasse, P. A. Schuller, F. … 展开作者

E. Pedretti, J. D. Monnier, S. Lacour, W. A. Traub, W. C. Danchi, P. G. Tuthill, N. D. Thureau, R. Millan-Gabet, J-P. Berger, M. G. Lacasse, P. A. Schuller, F. P. Schloerb, N. P. Carleton

摘要:

在IOTA干涉仪上,我们通过使用IONIC光束组合器测量精密闭合相位,检测到了共生星CH Cyg中的不对称性。不对称的位置随时间而变化,并与该恒星径向速度测量中发现的2.1年周期的相位相关。我们可以将时间相关的不对称性建模为围绕M巨星的低质量伴星的轨道,或者是M巨星上亮度变化20%的不对称性。在3年的监测期内,我们没有发现恒星大小的变化,无论是时间还是波长。我们发现在M巨星周围有一个发射尺寸为2.2+/-0.1 D* FWHM的球形尘埃壳层。恒星与尘埃的流量比估计为11.63+/-0.3。虽然最可能的解释是20%的亮度变化是非径向脉动,我们认为,一个低质量的同伴在近轨道可能是脉动的物理原因。脉动和低质量伴星的综合效应可以解释径向速度曲线和闭合相数据中检测到的随时间变化的不对称性所揭示的行为。如果天鹅座CH是一个典型的长次级周期变星,那么这些变化可以用主星上低质量伴星的轨道效应来解释。

英文摘要:

We have detected asymmetry in the symbiotic star CH Cyg through the measurement of precision closure-phase with the IONIC beam combiner, at the IOTA interferometer. The position of the asymmetry changes with time and is correlated with the phase of the 2.1-yr period found in the radial velocity measurements for this star. We can model the time-dependent asymmetry either as the orbit of a low-mass companion around the M giant or as an asymmetric, 20% change in brightness across the M giant. We do not detect a change in the size of the star during a 3 year monitoring period neither with respect to time nor with respect to wavelength. We find a spherical dust-shell with an emission size of 2.2+/-0.1 D* FWHM around the M giant star. The star to dust flux ratio is estimated to be 11.63+/-0.3. While the most likely explanation for the 20% change in brightness is non-radial pulsation we argue that a low-mass companion in close orbit could be the physical cause of the pulsation. The combined effect of pulsation and low-mass companion could explain the behaviour revealed by the radial-velocity curves and the time-dependent asymmetry detected in the closure-phase data. If CH Cyg is a typical long secondary period variable then these variations could be explained by the effect of an orbiting low-mass companion on the primary star.

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