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arXiv 0812.1799astro-ph
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一个冷的恒星点或第二个过境行星在TrES-1系统?

A cool starspot or a second transiting planet in the TrES-1 system?

M. Rabus, R. Alonso, J. A. Belmonte, H. J. Deeg, R. L. Gilliland, J. M. Almenara Villa, T. M. Brown, D. Charbonneau, G. Mandushev

摘要:

我们调查的起源,发现在过境的TrES-1,观察与HST的通量增加。HST光变曲线中的这一特征不能归因于噪声,而是被认为是主恒星表面的一个黑暗区域,在其过境期间被TrES-1所遮蔽。我们调查了其起源的两种可能假设的可能性:星点或第二颗凌日行星。我们利用了几个过境观测TrES-1从空间与HST和从地面与IAC-80望远镜。在这些观测的基础上,我们对每个观测事件中的通量变化进行了统计研究,以调查数据集的其他部分是否存在类似的通量增加。HST观测在凌日期间呈现出单一的明显通量上升,而地面观测导致检测到两个这样的事件,但意义不大。在HST数据中观察到一个恒星黑子的情况下,假设该黑子与TrES-1之间发生中心碰撞,我们将获得42000 km的黑子半径下限。对于这个半径,点的温度将是4690 K,比5250 K的恒星表面低560 K。对于假定的第二颗凌日行星,我们可以将其半径的下限设为0.37 R $_J$,对于周期小于10.5天的行星,我们可以将其半径的上限设为0.72 R $_J$。假设一个传统的解释,那么这个HST观测构成了一个星点的检测。或者,这种通量上升也可能是由另一颗过境行星引起的。如果通量上升的波长依赖性可以以更高的确定性显示或丢弃,则可以揭示起源的真实性质。此外,第二颗行星的存在也可以通过径向速度测量来检测。

英文摘要:

We investigate the origin of a flux increase found during a transit of TrES-1, observed with the HST. This feature in the HST light curve cannot be attributed to noise and is supposedly a dark area on the stellar surface of the host star eclipsed by TrES-1 during its transit. We investigate the likeliness of two possible hypothesis for its origin: A starspot or a second transiting planet. We made use of several transit observations of TrES-1 from space with the HST and from ground with the IAC-80 telescope. On the basis of these observations we did a statistical study of flux variations in each of the observed events, to investigate if similar flux increases are present in other parts of the data set. The HST observation presents a single clear flux rise during a transit whereas the ground observations led to the detection of two such events but with low significance. In the case of having observed a starspot in the HST data, assuming a central impact between the spot and TrES-1, we would obtain a lower limit for the spot radius of 42000 km. For this radius the spot temperature would be 4690 K, 560 K lower then the stellar surface of 5250 K. For a putative second transiting planet we can set a lower limit for its radius at 0.37 R$_J$ and for periods of less than 10.5 days, we can set an upper limit at 0.72 R$_J$. Assuming a conventional interpretation, then this HST observation constitutes the detection of a starspot. Alternatively, this flux rise might also be caused by an additional transiting planet. The true nature of the origin can be revealed if a wavelength dependency of the flux rise can be shown or discarded with a higher certainty. Additionally, the presence of a second planet can also be detected by radial velocity measurements.

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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