The GTC exoplanet transit spectroscopy survey X. Stellar spots versus Rayleigh scattering: the case of HAT-P-11b

doi:10.1051/0004-6361/201834063

	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
刊名	ASTRONOMY & ASTROPHYSICS
	2019-02-19
卷号	622 页码:12
关键词	planets and satellites: individual: HAT-P-11b planets and satellites: atmospheres techniques: spectroscopic
ISSN号	1432-0746
DOI	10.1051/0004-6361/201834063
通讯作者	Murgas, F.(fmurgas@iac.es)
英文摘要	Context. 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.
WOS关键词	TRANSMISSION SPECTRUM ; HD 189733B ; MODEL ATMOSPHERES ; ABSORPTION ; EFFICIENT ; HUBBLE ; SODIUM ; NOISE ; ORBIT ; STAR
WOS研究方向	Astronomy & Astrophysics
语种	英语
出版者	EDP SCIENCES S A
WOS记录号	WOS:000458945800001
内容类型	期刊论文
源URL	[http://libir.pmo.ac.cn/handle/332002/18660]
专题	中国科学院紫金山天文台
通讯作者	Murgas, F.
作者单位	1.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
推荐引用方式 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.