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The GTC exoplanet transit spectroscopy survey X. Stellar spots versus Rayleigh scattering: the case of HAT-P-11b
Murgas, F.1,2; Chen, G.1,2,3; Palle, E.1,2; Nortmann, L.1,2; Nowak, G.1,2
2019-02-19
Source PublicationASTRONOMY & ASTROPHYSICS
ISSN1432-0746
Volume622Pages:12
Corresponding AuthorMurgas, F.(fmurgas@iac.es)
AbstractContext. Rayleigh scattering in a hydrogen-dominated exoplanet atmosphere can be detected using ground-or space-based telescopes. However, stellar activity in the form of spots can mimic Rayleigh scattering in the observed transmission spectrum. Quantifying this phenomena is key to our correct interpretation of exoplanet atmospheric properties. Aims. We use the ten-meter Gran Telescopio Canarias (GTC) telescope to carry out a ground-based transmission spectra survey of extrasolar planets to characterize their atmospheres. In this paper we investigate the exoplanet HAT-P-11b, a Neptune-sized planet orbiting an active K-type star. Methods. We obtained long-slit optical spectroscopy of two transits of HAT-P-11b with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) on August 30, 2016 and September 25, 2017. We integrated the spectrum of HAT-P-11 and one reference star in several spectroscopic channels across the lambda similar to 400-785 nm region, creating numerous light curves of the transits. We fit analytic transit curves to the data taking into account the systematic effects and red noise present in the time series in an effort to measure the change of the planet-to-star radius ratio (R-p/R-s) across wavelength. Results. By fitting both transits together, we find a slope in the transmission spectrum showing an increase of the planetary radius towards blue wavelengths. Closer inspection of the transmission spectrum of the individual data sets reveals that the first transit presents this slope while the transmission spectrum of the second data set is flat. Additionally, we detect hints of Na absorption on the first night, but not on the second. We conclude that the transmission spectrum slope and Na absorption excess found in the first transit observation are caused by unocculted stellar spots. Modeling the contribution of unocculted spots to reproduce the results of the first night we find a spot filling factor of delta = 0.62(-0.17)(+0.20) and a spot-to-photosphere temperature difference of Delta T = 429(-299)(+184) K.
Keywordplanets and satellites: individual: HAT-P-11b planets and satellites: atmospheres techniques: spectroscopic
DOI10.1051/0004-6361/201834063
WOS KeywordTRANSMISSION SPECTRUM ; HD 189733B ; MODEL ATMOSPHERES ; ABSORPTION ; EFFICIENT ; HUBBLE ; SODIUM ; NOISE ; ORBIT ; STAR
Indexed BySCI
Language英语
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000458945800001
PublisherEDP SCIENCES S A
Citation statistics
Document Type期刊论文
Identifierhttp://libir.pmo.ac.cn/handle/332002/18661
Collection中国科学院紫金山天文台
Corresponding AuthorMurgas, F.
Affiliation1.IAC, Tenerife 38205, Spain
2.ULL, Dept Astrofis, Tenerife 38206, Spain
3.Chinese Acad Sci, Key Lab Planetary Sci, Purple Mt Observ, Nanjing 210008, Jiangsu, Peoples R China
Recommended Citation
GB/T 7714
Murgas, F.,Chen, G.,Palle, E.,et al. The GTC exoplanet transit spectroscopy survey X. Stellar spots versus Rayleigh scattering: the case of HAT-P-11b[J]. ASTRONOMY & ASTROPHYSICS,2019,622:12.
APA Murgas, F.,Chen, G.,Palle, E.,Nortmann, L.,&Nowak, G..(2019).The GTC exoplanet transit spectroscopy survey X. Stellar spots versus Rayleigh scattering: the case of HAT-P-11b.ASTRONOMY & ASTROPHYSICS,622,12.
MLA Murgas, F.,et al."The GTC exoplanet transit spectroscopy survey X. Stellar spots versus Rayleigh scattering: the case of HAT-P-11b".ASTRONOMY & ASTROPHYSICS 622(2019):12.
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