Photometric modelling of starspots – I. A Barnes–Evans‐like surface brightness–colour relation using (Ic−K)
Photometric modelling of starspots – I. A Barnes–Evans‐like surface brightness–colour relation using (Ic−K)
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星黑子的光度建模 – I. 使用 (Ic−K) 的类似 Barnes-Evans 的表面亮度-颜色关系
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发表时间：
1999
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影响因子：
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通讯作者：
P. Byrne
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作者：
P. Amado;C. J. Butler;P. Byrne
在这项工作的第一部分，恒星表面亮度FV与（Ic−K）宽带颜色的经验相关性进行了研究，通过使用比太阳冷的恒星样本。发现一个双线性相关可以很好地代表G、K和M巨星的亮度。斜率的变化发生在（Ic−K）= 2.1或大约从K到M光谱类型的过渡处。同样的关系也被调查的矮星，发现是明显不同的巨星。矮星星的相关性平均相差-0.4 in（Ic−K），最大值相差-0.1 in FV，低于巨星，在我们的样本中，两种趋势都倾向于较热恒星的收敛。由FV−（Ic-K）关系导出的巨星的流量分布，以及由FV−（V-K）关系和黑体流量分布导出的流量分布，计算了冷斑星的合成光V和色（V-R）c、（V-I）c和（V-K）曲线。我们调查的曲线振幅的影响，通过使用这些FV-颜色的关系，并通过假设的斑点的有效重力低于重力的unspotted光球。我们发现，使用FV−（Ic−K）关系产生的振幅大于其他两个亮度相关性产生的振幅，这意味着更小和/或更温暖的斑点。
In the first part of this work, the empirical correlation of stellar surface brightness FV with (Ic−K) broad-band colour is investigated by using a sample of stars cooler than the Sun. A bilinear correlation is found to represent well the brightness of G, K and M giant stars. The change in slope occurs at (Ic−K)∼2.1 or at about the transition from K to M spectral types. The same relationship is also investigated for dwarf stars and found to be distinctly different from that of the giants. The dwarf star correlation differs by an average of −0.4 in (Ic−K) or by a maximum in FV of ∼−0.1, positioning it below that of the giants, with both trends tending towards convergence for the hotter stars in our sample. The flux distribution derived from the FV−(Ic−K) relationship for the giant stars, together with that derived from an FV−(V−K) relationship and the blackbody flux distribution, is then utilized to compute synthetic light V and colour (V−R)c, (V−I)c and (V−K) curves of cool spotted stars. We investigate the effects on the amplitudes of the curves by using these FV–colour relations and by assuming the effective gravity of the spots to be lower than the gravity of the unspotted photosphere. We find that the amplitudes produced by using the FV−(Ic−K) relationship are larger than those produced by the other two brightness correlations, meaning smaller and/or warmer spots.