J/A+A/658/A133ivo://CDS.VizieR/J/A+A/658/A133doi:10.26093/cds/vizier.36580133CDSGressier A.Mori M.Changeat Q.Edwards B.Beaulieu J.P.Marcq E.,Charnay B.2022-05-18T12:48:46Z2022-02-10T08:33:33ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frmultiple-starsexoplanetsThe TRAPPIST-1 planetary system is favorable for transmission spectroscopy and offers the unique opportunity to study rocky-planets with possibly non-primary envelopes. We present here the transmission spectrum of the seventh planet of the TRAPPIST-1 system, TRAPPIST-1 h (R_P_=0.752R_{Earth}_, Teq=173K) using Hubble Space Telescope (HST), Wide Field Camera 3 Grism 141 (WFC3/G141) data. Our purpose is to reduce the HST observations of the seventh planet of TRAPPIST-1 system and by testing simple atmospheric hypothesis put new constraint on the composition and the nature of the planet. First we extracted and corrected the raw data to obtain a transmission spectrum in the Near-IR band (1.1-1.7um). TRAPPIST-1 is a cold M-dwarf and its activity could affect the transmission spectrum. We correct for stellar modulations using three different stellar contamination models, while some fit better the data, they are statistically not significant and the conclusion remains unchanged concerning the presence or not of an atmosphere. Finally, using a Bayesian atmospheric retrieval code we put new constraints on the atmosphere composition of TRAPPIST-1h. According to the retrieval analysis, there is no evidence of molecular absorption in the Near-InfraRed (NIR) spectrum. This suggests the presence of a high cloud deck or a layer of photochemical hazes in a primary atmosphere or a secondary atmosphere dominated by heavy species like nitrogen. This result could even be the consequence of the lack of an atmosphere as the spectrum is better fitted using a flat-line. Variations of transit depth around 1.3um are likely due to remaining scattering noise and results are not improved while changing the spectral resolution. TRAPPIST-1 h has probably lost its atmosphere or possesses a layer of clouds and hazes blocking the NIR signal. We can not distinguish yet between a primary cloudy or a secondary clear envelope using HST/WFC3 data but we can reject, in most cases with more than 3{sigma} confidence, the hypothesis of a clear atmosphere dominated by hydrogen and helium. By testing forced secondary atmospheric scenario, we find that a CO-rich atmosphere (i.e with a volume mixing ratio of 0.2) is one of the best fit to the spectrum with a Bayes Factor of 1.01 corresponding to a 2.1{sigma} detection.2022A&A...658A.133Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/658/A133CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/AJ/156/178 : NIR transmission spectra of TRAPPIST-1 planets (Zhang+, 2018)J/AJ/156/218 : Transit light curves of TRAPPIST-1 planets (Ducrot+, 2018)J/A+A/640/A112 : TRAPPIST-1 transit timings (Ducrot+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/658/A133https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/658/A133http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/658/A133https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/658/A133https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/658/A133http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/658/A133GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/658/A133/lc1Lightcurves of observations 1 taken in July 2017recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTime of exposure, BJD (TBD)dtime.epochdoublePhasePhase of transittime.phasedoubleFluxRawRaw flux (total count)phot.countintFluxNormNormalised corrected flux (detrended)phot.flux;arith.ratiodoubleResNormalised residuals between detrended and model (residuals)stat.fit.residualdoubleJ/A+A/658/A133/lc2Lightcurves of observations 2 taken in September 2019recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTime of exposure, BJD (TBD)dtime.epochdoublePhasePhase of transittime.phasedoubleFluxRawRaw flux (total count)phot.countintFluxNormNormalised corrected flux (detrended)phot.flux;arith.ratiodoubleResNormalised residuals between detrended and model (residuals)stat.fit.residualdoubleJ/A+A/658/A133/lc3Lightcurves of observations 3 taken in July 2020PhasePhase of transittime.phasedoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTime of exposure, BJD (TBD)dtime.epochdoubleFluxRawRaw flux (total count)phot.countintFluxNormNormalised corrected flux (detrended)phot.flux;arith.ratiodoubleResNormalised residuals between detrended and model (residuals)stat.fit.residualdouble