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arXiv 1004.0836astro-ph.EP
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系外行星WASP-1b和WASP-2b的热辐射

The thermal emission of the exoplanets WASP-1b and WASP-2b

Peter J. Wheatley, Andrew Collier Cameron, Joseph Harrington, Jonathan J. Fortney, James M. Simpson, David R. Anderson, Alexis M. S. Smith, Suzanne Aigrain, Wil… 展开作者

Peter J. Wheatley, Andrew Collier Cameron, Joseph Harrington, Jonathan J. Fortney, James M. Simpson, David R. Anderson, Alexis M. S. Smith, Suzanne Aigrain, William I. Clarkson, Michael Gillon, Carole A. Haswell, Leslie Hebb, Guillaume Hébrard, Coel Hellier, Simon T. Hodgkin, Keith D. Horne, Stephen R. Kane, Pierre F. L. Maxted, Andrew J. Norton, Don L. Pollacco, Frederic Pont, Ian Skillen, Barry Smalley, Rachel A. Street, Stephane Udry, Richard G. West, David M. Wilson

摘要:

我们提出了一个凌日系外行星WASP-1b和WASP-2b使用斯皮策太空望远镜的热辐射的比较研究。这两颗行星的质量非常相似,但受到的辐射水平不同,预计它们将落在有和没有热平流层的行星之间急剧过渡的两侧。WASP-1b是迄今为止研究过的辐射最高的行星之一。我们测量了两颗行星(3.6- 8.0 μ m)在所有四个IRAC波段的行星/恒星对比度,我们的结果表明WASP-1b的大气中存在强烈的温度反演,特别是在8 μ m处,而WASP-2b没有反演。在这两种情况下,测得的日食深度有利于入射能量不能有效地从地球的昼侧重新分配到夜侧的模型。我们拟合斯皮策光变曲线,同时与最好的径向速度曲线和过境测光,以提供最新的测量系统参数。我们在这两颗行星的轨道上都没有发现明显的偏心率,这表明WASP-1b膨胀的半径不太可能是潮汐加热的结果。最后,通过绘制所有已知行星在8 μ m和4.5 μ m处的次食深度与辐照度的比值,我们发现了在2 x 10^9 erg/s/cm ^2的辐照水平下,热彗星发射光谱急剧跃迁的证据。我们认为,这种转变可能是由于TiO的存在下,在最强烈的辐射热的超导体的上层大气中。

英文摘要:

We present a comparative study of the thermal emission of the transiting exoplanets WASP-1b and WASP-2b using the Spitzer Space Telescope. The two planets have very similar masses but suffer different levels of irradiation and are predicted to fall either side of a sharp transition between planets with and without hot stratospheres. WASP-1b is one of the most highly irradiated planets studied to date. We measure planet/star contrast ratios in all four of the IRAC bands for both planets (3.6-8.0um), and our results indicate the presence of a strong temperature inversion in the atmosphere of WASP-1b, particularly apparent at 8um, and no inversion in WASP-2b. In both cases the measured eclipse depths favor models in which incident energy is not redistributed efficiently from the day side to the night side of the planet. We fit the Spitzer light curves simultaneously with the best available radial velocity curves and transit photometry in order to provide updated measurements of system parameters. We do not find significant eccentricity in the orbit of either planet, suggesting that the inflated radius of WASP-1b is unlikely to be the result of tidal heating. Finally, by plotting ratios of secondary eclipse depths at 8um and 4.5um against irradiation for all available planets, we find evidence for a sharp transition in the emission spectra of hot Jupiters at an irradiation level of 2 x 10^9 erg/s/cm^2. We suggest this transition may be due to the presence of TiO in the upper atmospheres of the most strongly irradiated hot Jupiters.

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