Broadband transmission spectroscopy of HD 209458b with ESPRESSO: evidence for Na, TiO, or both

Abstract

Context. The detection and characterization of exoplanet atmospheres is currently one of the main drivers pushing the development of new observing facilities. In this context, high-resolution spectrographs are proving their potential and showing that high-resolution spectroscopy will be paramount in this field. Aims. We aim to make use of ESPRESSO high-resolution spectra, which cover two transits of HD 209458b, to probe the broadband transmission optical spectrum of the planet. Methods. We applied the chromatic Rossiter–McLaughin method to derive the transmission spectrum of HD 209458b. We compared the results with previous HST observations and with synthetic spectra. Results. We recover a transmission spectrum of HD 209458b similar to the one obtained with HST data. The models suggest that the observed signal can be explained by only Na, only TiO, or both Na and TiO, even though none is fully capable of explaining our observed transmission spectrum. Extra absorbers may be needed to explain the full dataset, though modeling approximations and observational errors can also be responsible for the observed mismatch. Conclusions. Using the chromatic Rossiter–McLaughlin technique, ESPRESSO is able to provide broadband transmission spectra of exoplanets from the ground, in conjunction with space-based facilities, opening good perspectives for similar studies of other planets.

Stellar obliquities in exoplanetary systems

“…It is also worth noting that in general, the v sin i value derived from line broadening is based on the disk-integrated stellar spectrum, whereas the value obtained by modeling the RM effect is more closely connected to the spectrum of the portion of the star hidden by the planet. Note-All data is taken from TEPCat (Southworth 2011) or the following references: 1 (Plavchan et al 2020), 2 (Hirano et al 2020a), 61 (Narita et al 2009b, 62 (Mann et al 2020), 63 (Liu et al 2018), 64 (Hébrard et al 2010), 65 (Crossfield et al 2017), 66 (Zhou et al 2018), 67 (Cegla et al 2016), 68 (Santos et al 2020), 69 (Rizzuto et al 2020), 70 (Heitzmann et al 2021), 71 (Mann et al 2016), 72 (Stefansson et al 2020), 73 (Santerne et al 2016), 74 (Hirano et al 2016), 75 (Korth et al 2019), 76 (Rice et al 2021), 77 (Brahm et al 2018), 78 (Wang et al 2021a), 79 (Hjorth et al 2019a), 80 (Siverd et al 2012), 81 (Damasso et al 2015a), 82 (Bieryla et al 2015), 83 (Gaudi et al 2017), 84 (Wyttenbach et al 2020), 85 (Zhou et al 2016b), 86 (Siverd et al 2018), 87 (Johnson et al 2018), 88 (Rodríguez Martínez et al 2020, 89 (Holman et al 2010), 90 (Wang et al 2018), 91 (Szabó et al 2011), 92 (Howarth & Morello 2017, 93 (Désert et al 2011…”

A Preponderance of Perpendicular Planets

“…(Albrecht et al 2012b), 9(Masuda 2015), 10(Lund et al 2014), 11(Béky et al 2014), 12(Winn et al 2010), 13 (Sanchis-Ojeda & Winn 2011), 14(Esposito et al 2017), 15(Mancini et al 2018), 16(Mancini et al 2015), 17 (Mohler-Fischer et al 2013, 18(Mann et al 2020), 19(Dai et al 2020), 20(Henry & Winn 2008), 21(Cegla et al 2016), 22 (Maxted et al 2015, 23(Santos et al 2020), 24(Stefansson et al 2020), 25(Santerne et al 2016), 26(Hjorth et al 2019), 27(Hjorth et al 2021), 28(Wyttenbach et al 2020), 29(Ahlers et al 2020), 30(Zhou et al 2016), 31(Wang et al 2018), 32(Howarth & Morello 2017), 33(Désert et al 2011), 34 (McQuillan et al 2013, 35(Albrecht et al 2013), 36 (Sanchis-Ojeda et al 2013, 37(Johnson et al 2017), 38(Dorval et al 2020), 39(Mislis et al 2015), 40(Covino et al 2013), 41(Dai et al 2017), 42(Bryan et al 2012), 43(Močnik et al 2017), 44(Hirano et al 2020b), 45 (Sanchis-Ojeda et al 2011), 46 (Triaud et al 2010, 47(Gillon et al 2009), 48 (Tregloan-Reed et al 2015, 49(Albrecht et al 2012a), 50(Bourrier et al 2017), 51 (Tregloan-Reed et al 2013, 52(Brothwell et al 2014), 53(Brown et al 2012), 54(Johnson et al 2015), 55(Southworth et al 2016), 56…”

A Spectral Survey of WASP-19b with ESPRESSO

“…A secondary channel through which an exoplanetary atmosphere could be probed from high resolution observations is the chromatic Rossiter-McLaughlin (CRM) measurement (e.g. Di Gloria et al 2015;Boldt et al 2020;Oshagh et al 2020;Palle et al 2020;Santos et al 2020). This approach involves the determination of exoplanetary apparent radius variations as a function of wavelength, analogous to low resolution studies.…”

“…The CCF's from all pairs of slices of each order were weight combined (85 spectral orders in total) of which 8 were discarded 11 due to large systematic noise attributed to the presence of very deep or saturated telluric lines. We firstly determined the minimum number of spectral orders that needed to be binned in order to produce reasonably precise RM curves, similar to the systematic study performed by Santos et al (2020), and was set to 5 spectral orders (10 slices). All these combined CCF's were fitted with a Gaussian function, using a Levenberg-Marquardt algorithm to solve the minimization relation, whose mean value is the RV and its estimated error is taken from the covariance matrix.…”

“…Finally, chromatic Rossiter-McLaughlin (CRM;Snellen 2004;Dreizler et al 2009) measurements can probe the atmosphere of a transiting exoplanet in a similar manner to spectrophotometric studies by measuring the planetary radius as a function of wavelength (e.g. Di Gloria et al 2015;Borsa et al 2016Borsa et al , 2021Boldt et al 2020;Oshagh et al 2020;Santos et al 2020). This final approach comes at no extra observational cost and allows to probe different atmospheric layers from the same set of observations.…”