Chromatic line-profile tomography to reveal exoplanetary atmospheres: application to HD 189733b

Borsa, F.; Rainer, M.; Poretti, E.

doi:10.1051/0004-6361/201628334

Cited by 14 publications

(14 citation statements)

References 33 publications

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“…Our result are in line with with these values. The measured angular rotation of the star (ω = 0.559±0.003 rad/day) is also consistent with the equatorial period of 11.94 ± 0.16 days presented in Fares et al (2010), and the resulting linear limb darkening coefficient ( = 0.876±0.011) is very similar to the one presented in Borsa et al (2016) calculated over the HARPS wavelength range (0.7962 ± 0.0013).…”

Section: The Rossiter-mclaughlin Effect Of Wasp-69bsupporting

confidence: 85%

Detection of sodium in the atmosphere of WASP-69b

Casasayas-Barris¹,

Πάλλη²,

Nowak³

et al. 2017

A&A

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Context. Transit spectroscopy is one of the most commonly used methods to characterize exoplanets' atmospheres. From the ground, these observations are very challenging due to the terrestrial atmosphere and its intrinsic variations, but high-spectral resolution observations overcome this difficulty by resolving the spectral lines and taking advantage of the different Doppler velocities of the Earth, the host star and the exoplanet. Aims. We analyze the transmission spectrum around the Na I doublet at 589 nm of the extrasolar planet WASP-69b, a hot Jupiter orbiting a K-type star with a period of 3.868 days, and compare the analysis to that of the well-know hot Jupiter HD 189733b. We also present the analysis of the Rossiter-McLaughlin effect for WASP-69b. Methods. We observed two transits of WASP-69b with the High Accuracy Radial velocity Planet Searcher (HARPS-North) spectrograph (R = 115 000) at the TNG telescope. We perform a telluric contamination subtraction based on the comparison between the observed spectra and a telluric water model. Then, the common steps of the differential spectroscopy are followed to extract the transmission spectrum. The method is tested with archival transit data of the extensively studied exoplanet HD 189733b, obtained with the HARPS-South spectrograph at ESO 3.6 m telescope, and then applied to WASP-69b data. Results. For HD 189733b, we spectrally resolve the Na I doublet and measure line contrasts of 0.72 ± 0.05 % (D2) and 0.51 ± 0.05 % (D1), and FWHMs of 0.64 ± 0.04 Å (D2) and 0.60 ± 0.06 Å (D1), in agreement with previously published results. For WASP-69b only the contrast of the D2 line can be measured (5.8 ± 0.3 %). This corresponds to a detection at the 5σ-level of excess absorption of 0.5±0.1 % in a passband of 1.5 Å. A net blueshift of ∼0.04 Å is measured for HD 189733b and no shift is obtained for WASP-69b. By measuring the Rossiter-McLaughlin (RM) effect, we get an angular rotation of 0.24 +0.02 −0.01 rad/day and a sky-projected angle between the stellar rotation axis and the normal of orbit plane (λ) of 0.4 +2.0 −1.9 o for WASP-69b. Similar results to those previously presented in the literature are obtained for the RM analysis of HD 189733b. Conclusions. Even if sodium features are clearly detected in the WASP-69b transmission spectrum, more transits are needed to fully characterize the lines profiles and retrieve accurate atmospheric properties.

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Section: The Rossiter-mclaughlin Effect Of Wasp-69bsupporting

confidence: 85%

Detection of sodium in the atmosphere of WASP-69b

Casasayas-Barris¹,

Πάλλη²,

Nowak³

et al. 2017

A&A

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“…Being slightly larger than Jupiter, the apparent radius of the planet was deduced from observations with the ACS instrument on the HST as 0.1572 ± 0.0004 R (Pont et al 2007), while various wavelength passbands in the HST STIS instrument yielded values between 0.15617 and 0.15754 R (Sing et al 2011). Ground-based data show only very slight variation among various wavelength bands in the optical (Borsa et al 2016). Even in the far-infrared, the relative area covered by the planet (the square of these numbers, 2.46%) remains about the same (Agol et al 2010;Beaulieu et al 2008).…”

Section: Planet Hd 189733abmentioning

confidence: 99%

Spatially resolved spectroscopy across stellar surfaces

Dravins

Gustavsson

Ludwig

2018

A&A

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Context. Spectroscopy across spatially resolved stellar surfaces reveals spectral line profiles free from rotational broadening, whose gradual changes from disk center toward the stellar limb reflect an atmospheric fine structure that is possible to model by 3D hydrodynamics. Aims. Previous studies of photospheric spectral lines across stellar disks exist for the Sun and HD 209458 (G0 V) and are now extended to the planet-hosting HD 189733A to sample a cooler K-type star and explore the future potential of the method. Methods. During exoplanet transit, stellar surface portions successively become hidden and differential spectroscopy between various transit phases uncovers spectra of small surface segments temporarily hidden behind the planet. The method was elaborated in Paper I, in which observable signatures were predicted quantitatively from hydrodynamic simulations. Results. From observations of HD 189733A with the ESO HARPS spectrometer at λ/Δλ~ 115 000, profiles for stronger and weaker Fe I lines are retrieved at several center-to-limb positions, reaching adequate S/N after averaging over numerous similar lines. Conclusions. Retrieved line profile widths and depths are compared to synthetic ones from models with parameters bracketing those of the target star and are found to be consistent with 3D simulations. Center-to-limb changes strongly depend on the surface granulation structure and much greater line-width variation is predicted in hotter F-type stars with vigorous granulation than in cooler K-types. Such parameters, obtained from fits to full line profiles, are realistic to retrieve for brighter planet-hosting stars, while their hydrodynamic modeling offers previously unexplored diagnostics for stellar atmospheric fine structure and 3D line formation. Precise modeling may be required in searches for Earth-analog exoplanets around K-type stars, whose more tranquil surface granulation and lower ensuing microvariability may enable such detections.

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“…The numerical simulations performed by Dreizler et al (2009) proved the feasibility of this technique. Recently, Di Gloria et al (2015) and Borsa et al (2016) presented the first application of this technique on the transiting planet HD189733 b, and obtained the slope in the transmission spectrum of HD189733 b, which was interpreted as the Rayleigh scattering in the planet atmosphere. We would like to note that the RM anomalies may also affect the planet radius estimation through the RM observations.…”

Section: Probing the Impact Of Rm Observation At Different Wavelengthmentioning

confidence: 99%

Can stellar activity make a planet seem misaligned?

Oshagh

Santos

Figueira

et al. 2016

A&A

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Several studies have shown that the occultation of stellar active regions by the transiting planet can generate anomalies in the high-precision transit light curves, and these anomalies may lead to an inaccurate estimate of the planetary parameters (e.g., the planet radius). Since the physics and geometry behind the transit light curve and the RossiterMcLaughlin effect (spectroscopic transit) are the same, the Rossiter-McLaughlin observations are expected to be affected by the occultation of stellar active regions in a similar way. In this paper we perform a fundamental test on the spin-orbit angles as derived by Rossiter-McLaughlin measurements, and we examine the impact of the occultation of stellar active regions by the transiting planet on the spin-orbit angle estimations. Our results show that the inaccurate estimation on the spin-orbit angle due to stellar activity can be quite significant (up to ∼ 30 degrees), particularly for the edge-on, aligned, and small transiting planets. Therefore, our results suggest that the aligned transiting planets are the ones that can be easily misinterpreted as misaligned owing to the stellar activity. In other words, the biases introduced by ignoring stellar activity are unlikely to be the culprit for the highly misaligned systems.

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Chromatic line-profile tomography to reveal exoplanetary atmospheres: application to HD 189733b

Cited by 14 publications

References 33 publications

Detection of sodium in the atmosphere of WASP-69b

Detection of sodium in the atmosphere of WASP-69b

Spatially resolved spectroscopy across stellar surfaces

Can stellar activity make a planet seem misaligned?

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