Na I and H alpha absorption features in the atmosphere of MASCARA-2b/KELT-20b
Casasayas-Barris, N.1,2; Palle, E.1,2; Yan, F.3; Chen, G.1,2,4; Albrecht, S.5; Nortmann, L.1,2; Van Eylen, V.6; Snellen, I.6; Talens, G. J. J.6; Gonzalez Hernandez, J. I.1,2; Rebolo, R.1,2,7; Otten, G. P. P. L.6
Corresponding AuthorCasasayas-Barris, N.(
AbstractWe used the HARPS-North high resolution spectrograph (R = 115 000) at Telescopio Nazionale Galileo (TNG) to observe one transit of the highly irradiated planet MASCARA-2b/KELT-20b. Using only one transit observation, we are able to clearly resolve the spectral features of the atomic sodium (Na I) doublet and the H alpha line in its atmosphere, which are corroborated with the transmission calculated from their respective transmission light curves (TLC). In particular, we resolve two spectral features centered on the Na I doublet position with an averaged absorption depth of 0.17 +/- 0.03% for a 0.75 angstrom bandwidth with line contrasts of 0.44 +/- 0.11% (D-2) and 0.37 +/- 0.08% (D-1). The Na I TLC have also been computed, showing a large Rossiter-McLaughlin (RM) effect, which has a 0.20 +/- 0.05% Na I transit absorption for a 0.75 angstrom passband that is consistent with the absorption depth value measured from the final transmission spectrum. We observe a second feature centered on the H alpha line with 0.6 +/- 0.1% contrast and an absorption depth of 0.59 +/- 0.08% for a 0.75 angstrom passband that has consistent absorptions in its TLC, which corresponds to an effective radius of R-lambda/R-P = 1.20 +/- 0.04. While the signal-to-noise ratio (S/N) of the final transmission spectrum is not sufficient to adjust different temperature profiles to the lines, we find that higher temperatures than the equilibrium (T-eq = 2260 +/- 50K) are needed to explain the lines contrast. Particularly, we find that the Na I lines core require a temperature of T = 4210 +/- 180K and that H alpha requires a temperature of T = 4330 +/- 520 K. MASCARA-2b, like other planets orbiting A-type stars, receives a large amount of UV energy from its host star. This energy excites the atomic hydrogen and produces H alpha absorption, leading to the expansion and abrasion of the atmosphere. The study of other Balmer lines in the transmission spectrum would allow the determination of the atmospheric temperature profile and the calculation of the lifetime of the atmosphere with escape rate measurements. In the case of MASCARA-2b, residual features are observed in the H beta and H gamma lines, but they are not statistically significant. More transit observations are needed to confirm our findings in Na I and H alpha and to build up enough S/N to explore the presence of H beta and H gamma planetary absorptions.
Keywordplanetary systems techniques: spectroscopic planets and satellites: atmospheres methods: observational planets and satellites: individual: MASCARA-2b planets and satellites: individual: KELT-20b
Indexed BySCI
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000444016100001
Citation statistics
Cited Times:11[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Corresponding AuthorCasasayas-Barris, N.
Affiliation1.Inst Astrofis Canarias, Via Lactea S-N, Tenerife 38205, Spain
2.Univ La Laguna, Dept Astrofis, San Cristobal la Laguna, Spain
3.Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany
4.Chinese Acad Sci, Key Lab Planetary Sci, Purple Mt Observ, Nanjing 210008, Peoples R China
5.Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
6.Leiden Univ, Leiden Observ, Postbus 9513, NL-2300 RA Leiden, Netherlands
7.CSIC, Madrid, Spain
Recommended Citation
GB/T 7714
Casasayas-Barris, N.,Palle, E.,Yan, F.,et al. Na I and H alpha absorption features in the atmosphere of MASCARA-2b/KELT-20b[J]. ASTRONOMY & ASTROPHYSICS,2018,616:14.
APA Casasayas-Barris, N..,Palle, E..,Yan, F..,Chen, G..,Albrecht, S..,...&Otten, G. P. P. L..(2018).Na I and H alpha absorption features in the atmosphere of MASCARA-2b/KELT-20b.ASTRONOMY & ASTROPHYSICS,616,14.
MLA Casasayas-Barris, N.,et al."Na I and H alpha absorption features in the atmosphere of MASCARA-2b/KELT-20b".ASTRONOMY & ASTROPHYSICS 616(2018):14.
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