J/A+A/616/A151 MASCARA-2b NaI & Ha absorption lines (Casasayas-Barris+, 2018)
Na I and Hα absorption features in the atmosphere of MASCARA-2b/KELT-20b.
Casasayas-Barris N., Palle E., Yan F., Chen G., Albrecht S., Nortmann L.,
Van Eylen V., Snellen I., Talens G.J.J., Gonzalez Hernandez J.I.,
Rebolo R., Otten G.P.P.L.
<Astron. Astrophys. 616, A151 (2018)>
=2018A&A...616A.151C 2018A&A...616A.151C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Spectroscopy
Keywords: planetary systems - techniques: spectroscopic -
planets and satellites: atmospheres - methods: observational -
planets and satellites: individual: MASCARA-2b -
planets and satellites: individual: KELT-20b
Abstract:
We used the HARPS-North high resolution spectrograph (R=115000) 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 (NaI) doublet and the Hα 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 centred on the NaI doublet position
with an averaged absorption depth of 0.17±0.03% for a 0.75Å
bandwidth with line contrasts of 0.44±0.11% (D2) and 0.37±0.08%
(D1). The NaI TLC have also been computed, showing a large
Rossiter-McLaughlin (RM) effect, which has a 0.20±0.05% NaI transit
absorption for a 0.75Å passband that is consistent with the
absorption depth value measured from the final transmission spectrum.
We observe a second feature centred on the Hα line with
0.6±0.1% contrast and an absorption depth of 0.59±0.08% for a
0.75Å passband that has consistent absorptions in its TLC, which
corresponds to an effective radius of R'/Rp=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 (Teq=2260±50K)
are needed to explain the lines contrast. Particularly, we find that
the NaI lines core require a temperature of T=4210±180K and that
Hα requires a temperature of T=4330±520K. 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 Hα 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 Hβ and Hγ lines, but they are not
statistically significant.More transit observations are needed to
confirm our findings in NaI and Hα and to build up enough S/N to
explore the presence of Hβ and Hγ planetary absorptions.
Description:
The transmission spectra and transmission light curves of MASCARA-2b
around the Na and Hα are presented. The transmission light
curves are calculated for 0.75, 1.5, 3.0 and 5Å bandwidths for NaI,
and 3, 5, 10, and 20Å bandwidths for the Hα line. Only one
transit of MASCARA-2b with HARPS-North at TNG telescope were retrieved
to obtain these results.
Objects:
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RA (2000) DE Designation(s)
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19 38 38.74 +31 13 09.2 MASCARA-2b = KELT-20b
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tsm2bna.dat 36 1901 Transmission spectrum around Na
tsm2bha.dat 36 7002 Transmission spectrum around Hα
lcm2bna.dat 90 90 Transmission light curves around Na
lcm2bha.dat 90 90 Transmission light curves around Hα
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See also:
J/A+A/612/A57 : MASCARA-2 b (HD185603) light curves and spectra (Talens+, 2018)
Byte-by-byte Description of file: tsm2bha.dat tsm2bna.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm lambda Wavelength in Angstroem
9- 22 E14.13 % Flux Relative Flux in % (1)
24- 36 E13.12 % e_Flux Error in relative flux
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Note (1): The final transmission spectrum (F) is the result of a ratio between
spectra. We present the data in % with the continuum in the 0 level by
applying (F-1.0)*100. [%].
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Byte-by-byte Description of file: lcm2bna.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.7 --- Phase Orbital phase
12- 20 F9.7 --- Flux075 Relative Flux in a 0.75 Angstroem passband (1)
22- 30 F9.7 --- e_Flux075 Errors for a 0.75A passband
32- 40 F9.7 --- Flux150 Relative Flux in a 1.50 Angstroem passband (1)
42- 50 F9.7 --- e_Flux150 Errors for a 1.50A passband
52- 60 F9.7 --- Flux300 Relative Flux in a 3.0 Angstroem passband (1)
62- 70 F9.7 --- e_Flux300 Errors for a 3.0A passband
72- 80 F9.7 --- Flux500 Relative Flux in a 5.0 Angstroem passband (1)
82- 90 F9.7 --- e_Flux500 Errors for a 5.0A passband
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Note (1): The flux values are the result of ratios between spectra.
The presented values are normalised to 1.
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Byte-by-byte Description of file: lcm2bha.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.7 --- Phase Orbital phase
12- 20 F9.7 --- Flux300 Relative Flux in a 3.00 Angstrom passband (1)
22- 30 F9.7 --- e_Flux300 Errors for a 3.00A passband
32- 40 F9.7 --- Flux500 Relative Flux in a 5.00 Angstrom passband (1)
42- 50 F9.7 --- e_Flux500 Errors for a 5.00A passband
52- 60 F9.7 --- Flux1000 Relative Flux in a 10.0 Angstrom passband (1)
62- 70 F9.7 --- e_Flux1000 Errors for a 10.0A passband
72- 80 F9.7 --- Flux2000 Relative Flux in a 20.0 Angstrom passband (1)
82- 90 F9.7 --- e_Flux2000 Errors for a 20.0A passband
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Note (1): The flux values are the result of ratios between spectra.
The presented values are normalised to 1.
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Acknowledgements:
Nuria Casasayas-Barris, nuriacb(at)iac.es
(End) Nuria Casasayas-Barris [IAC, Spain], Patricia Vannier [CDS] 27-Jul-2018