J/A+A/587/A67 WASP-49b FORS2 multi-epoch spectra (Lendl+, 2016)
FORS2 observes a multi-epoch transmission spectrum of the hot Saturn-mass
exoplanet WASP-49b.
Lendl M., Delrez L., Gillon M., Madhusudhan N., Jehin E., Queloz D.,
Anderson D.R., Demory B.-O., Hellier C.
<Astron. Astrophys. 587, A67 (2016)>
=2016A&A...587A..67L 2016A&A...587A..67L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Planets ; Photometry
Keywords: techniques: spectroscopic - planets and satellites: atmospheres -
stars: individual: WASP-49 - planets and satellites: gaseous planets
Abstract:
Transmission spectroscopy has proven to be a useful tool for the study
of exoplanet atmospheres, because the absorption and scattering
signatures of the atmosphere manifest themselves as variations in the
planetary transit depth. Several planets have been studied with this
technique, leading to the detection of a small number of elements and
molecules (Na, K, H2O), but also revealing that many planets show
flat transmission spectra consistent with the presence of opaque
high-altitude clouds.
We apply this technique to the Mp=0.40 Mjup, Rp=1.20Rjup, P=2.78d
planet WASP-49b, aiming to characterize its transmission spectrum
between 0.73 and 1um and search for the features of K and H2O. Owing
to its density and temperature, the planet is predicted to possess an
extended atmosphere and is thus a good target for transmission
spectroscopy.
Three transits of WASP-49b have been observed with the FORS2
instrument installed at the VLT/UT1 telescope at the ESO Paranal site.
We used FORS2 in MXU mode with grism GRIS_600z, producing simultaneous
multiwavelength transit light curves throughout the i' and z' bands.
We combined these data with independent broadband photometry from the
Euler and TRAPPIST telescopes to obtain a good measurement of the
transit shape. Strong correlated noise structures are present in the
FORS2 light curves, which are due to rotating flat-field structures
that are introduced by inhomogeneities of the linear atmospheric
dispersion corrector's transparency. We accounted for these structures
by constructing common noise models from the residuals of light curves
bearing the same noise structures and used them together with simple
parametric models to infer the transmission spectrum.
We present three independent transmission spectra of WASP-49b between
0.73 and 1.02um, as well as a transmission spectrum between 0.65 and
1.02um from the combined analysis of FORS2 and broadband data. The
results obtained from the three individual epochs agree well. The
transmission spectrum of WASP-49b is best fit by atmospheric models
containing a cloud deck at pressure levels of 1mbar or lower.
Description:
We present spectro-photometric time-series obtained with FORS2, and
the broadband data observed with EulerCam and TRAPPIST. All data were
obtained during transits of WASP-49b.
Objects:
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RA (2000) DE Designation(s)
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06 04 21.46 -16 57 55.06 WASP-49 = 2MASS J06042146-1657550
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
broadb.dat 78 4789 Broadband photometry
fors2_01.dat 58 839 FORS2 738-748nm spectrophotometry
fors2_02.dat 58 839 FORS2 748-758nm spectrophotometry
fors2_03.dat 58 839 FORS2 758-768nm spectrophotometry
fors2_04.dat 58 839 FORS2 768-778nm spectrophotometry
fors2_05.dat 58 839 FORS2 778-788nm spectrophotometry
fors2_06.dat 58 839 FORS2 765-773nm spectrophotometry
fors2_07.dat 58 778 FORS2 788-798nm spectrophotometry
fors2_08.dat 58 778 FORS2 798-808nm spectrophotometry
fors2_09.dat 58 778 FORS2 808-818nm spectrophotometry
fors2_10.dat 58 778 FORS2 818-828nm spectrophotometry
fors2_11.dat 58 778 FORS2 828-838nm spectrophotometry
fors2_12.dat 58 778 FORS2 838-848nm spectrophotometry
fors2_13.dat 58 778 FORS2 848-858nm spectrophotometry
fors2_14.dat 58 778 FORS2 858-868nm spectrophotometry
fors2_15.dat 58 778 FORS2 868-878nm spectrophotometry
fors2_16.dat 58 778 FORS2 878-888nm spectrophotometry
fors2_17.dat 58 778 FORS2 888-898nm spectrophotometry
fors2_18.dat 58 837 FORS2 898-908nm spectrophotometry
fors2_19.dat 58 837 FORS2 908-918nm spectrophotometry
fors2_20.dat 58 837 FORS2 918-928nm spectrophotometry
fors2_21.dat 58 837 FORS2 928-938nm spectrophotometry
fors2_22.dat 58 837 FORS2 938-948nm spectrophotometry
fors2_23.dat 58 837 FORS2 948-958nm spectrophotometry
fors2_24.dat 58 837 FORS2 958-968nm spectrophotometry
fors2_25.dat 58 837 FORS2 968-978nm spectrophotometry
fors2_26.dat 58 837 FORS2 978-988nm spectrophotometry
fors2_27.dat 58 837 FORS2 988-1000nm spectrophotometry
fors2_28.dat 58 837 FORS2 1000-1020nm spectrophotometry
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See also:
J/A+A/544/A72 : WASP-42 and WASP-49 photometry and velocities (Lendl+, 2012)
Byte-by-byte Description of file: broadb.dat
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Bytes Format Units Label Explanations
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1- 11 F11.6 d HJD Heliocentric Julian Date (HJD-2450000)
12- 20 F9.6 --- Flux Normalized Flux
21- 29 F9.6 --- e_Flux Normalized Flux error
30- 36 F7.2 pix xshift Pixel shift in x-direction
37- 43 F7.2 pix yshift Pixel shift in y-direction
44- 49 F6.2 pix FWHM Stellar full width at half maximum
50- 56 F7.2 --- Sky Sky level (Flux)
57- 61 F5.2 --- AM Airmass
62- 66 F5.1 s ExpTime Exposure time
67- 69 A3 --- Filt Filter
70- 78 A9 --- Inst Instrument
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Byte-by-byte Description of file: fors2_*.dat
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Bytes Format Units Label Explanations
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1- 11 F11.6 d HJD Heliocentric Julian Date (HJD-2450000)
12- 20 F9.6 --- Flux Normalized Flux
21- 29 F9.6 --- e_Flux Normalized Flux error
30- 34 F5.2 pix FWHM Spectrum full width at half maximum
35- 41 F7.2 deg Par Parallactic angle
42- 48 F7.2 --- Sky Sky level (Flux)
49- 53 F5.2 --- AM Airmass
54- 58 F5.1 s ExpTime Exposure time
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Acknowledgements:
Monika Lendl, monika.lendl(at)oeaw.ac.at
(End) Patricia Vannier [CDS] 13-Jan-2016