Near-UV Absorption, Chromospheric Activity, and Star-Planet Interactions in the WASP-12 system
Near-UV Absorption, Chromospheric Activity, and Star-Planet Interactions in the WASP-12 system
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DOI：
10.1088/0004-637x/760/1/79
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发表时间：
2013-01
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通讯作者：
C. Haswell;L. Fossati;T. Ayres;K. France;C. Froning;S. Holmes;U. Kolb;R. Busuttil;R. Street;L. Hebb;A. Cameron;B. Enoch;V. Burwitz;J. Rodriguez;R. West;D. Pollacco;P. Wheatley;A. Carter
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作者：
C. Haswell;L. Fossati;T. Ayres;K. France;C. Froning;S. Holmes;U. Kolb;R. Busuttil;R. Street;L. Hebb;A. Cameron;B. Enoch;V. Burwitz;J. Rodriguez;R. West;D. Pollacco;P. Wheatley;A. Carter
我们用HST观测了极近热木星系统WASP-12。WASP-12 b的近紫外线传输比光学传输深三倍，显示出广泛的扩散气体，远远超出了罗氏瓣。吸收气体的分布在不同的访问之间变化。最深的NUV凌日是在具有强烈光球吸收的波长范围内，这意味着吸收气体可能具有与恒星光球相似的温度和成分。我们的光谱显示，在两次HST访问中的每一次访问中，在约200个波长处的吸收显著增强（低于中值大于3 \sigma）;其中65个波长在两次访问之间是一致的，使用严格的速度匹配标准，该标准排除了速度变化超过约20 km/s的匹配。多余的过境深度稳健检测整个内翼的MgII共振线独立的两个HST访问。我们在FeII 2586 A中检测到吸收，这是在系外行星过境中检测到的最重的物种。MgII线核的通量为零，其他观测到的年龄和光谱类型相似的星星的发射核明显缺失。WASP-12可能产生正常的MgII配置文件，但这些强共振线的内部部分可能受到外来吸收的影响。所需的Mg+柱比ISM预期的大一个数量级，尽管我们不能完全排除这种可能性。一个更合理的吸收来源是WASP-12 b损失的气体。我们表明，行星质量损失可以产生所需的列。我们的第二次访问NUV光变曲线显示了恒星耀斑的证据。我们表明，一些可能的过境检测稀有元素的共振线可能是由于在共同的物种，而不是非共振跃迁。我们提出了光学观测和更新的过境星历。
We observed the extreme close-in hot Jupiter system WASP-12 with HST. Near-UV transits up to three times deeper than the optical transit of WASP-12b reveal extensive diffuse gas, extending well beyond the Roche lobe. The distribution of absorbing gas varies between visits. The deepest NUV transits are at wavelength ranges with strong photospheric absorption, implying the absorbing gas may have temperature and composition similar to the stellar photosphere. Our spectra reveal significantly enhanced absorption (greater than 3 \sigma below the median) at ~200 wavelengths on each of two HST visits; 65 of these wavelengths are consistent between the two visits, using a strict criterion for velocity matching which excludes matches with velocity shifts exceeding ~20 km/s. Excess transit depths are robustly detected throughout the inner wings of the MgII resonance lines independently on both HST visits. We detected absorption in FeII 2586A, the heaviest species yet detected in an exoplanet transit. The MgII line cores have zero flux, emission cores exhibited by every other observed star of similar age and spectral type are conspicuously absent. WASP-12 probably produces normal MgII profiles, but the inner portions of these strong resonance lines are likely affected by extrinsic absorption. The required Mg+ column is an order of magnitude greater than expected from the ISM, though we cannot completely dismiss that possibility. A more plausible source of absorption is gas lost by WASP-12b. We show that planetary mass loss can produce the required column. Our Visit 2 NUV light curves show evidence for a stellar flare. We show that some of the possible transit detections in resonance lines of rare elements may be due instead to non-resonant transitions in common species. We present optical observations and update the transit ephemeris.