HST hot-Jupiter transmission spectral survey: haze in the atmosphere of WASP-6b

Nikolov, Nikolay; Sing, David K.; Burrows, Adam; Fortney, Jonathan J.; Henry, Gregory W.; Pont, F.; Ballester, G. E.; Aigrain, S.; Wilson, Paul; Huitson, Catherine M.; Gibson, Neale P.; Désert, Jean-Michel; Étangs, A. Lecavelier des; Showman, Adam P.; Vidal‐Madjar, A.; Wakeford, Hannah R.; Zahnle, Kevin

doi:10.1093/mnras/stu2433

Cited by 154 publications

(156 citation statements)

References 80 publications

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“…For this reason, we performed a two-color monitoring campaign for HAT-P-19 using the 1.2 m telescope STELLA on Tenerife over a time span of about 300 days. Similar studies can be found in the literature for the hot-Jupiter host stars HD 189733 , WASP-19 (Huitson et al 2013), WASP-12 ), HAT-P-1 (Nikolov et al 2014), WASP-6 (Nikolov et al 2015), and WASP-31 . This paper is structured as follows: Sect.…”

Section: Introductionsupporting

confidence: 89%

“…Murgas et al (2014) presented a probable detection of Na for WASP-43b and a tentative detection of K was given by Nikolov et al (2015). The (low-resolution) non-detection in the atmospheres of HD 189733b and WASP-12b can be explained by scattering particles blocking the atmospheric heights that are possible for atomic sodium and potassium (Pont et al 2008;Sing et al 2013).…”

Section: Introductionmentioning

confidence: 96%

“…Furthermore, it was ruled out for the somewhat cooler atmospheres of HAT-P-1b (Nikolov et al 2014). The non-detection of TiO in HD 189733b, HAT-P-32b, WASP-31b, and WASP-6b can be explained by clouds or haze on top of the atmosphere (Pont et al 2008;Gibson et al 2013b;Sing et al 2015;Nikolov et al 2015). …”

Section: Introductionmentioning

confidence: 99%

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Transmission spectroscopy of the inflated exo-Saturn HAT-P-19b

Mallonn

Essen

Weingrill

et al. 2015

A&A

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Context. Transiting highly inflated giant planets offer the possibility of characterizing their atmospheres. A fraction of the starlight passes through the high-altitude layers of the planetary atmosphere during transit. The resulting absorption is expected to be wavelength dependent for cloud-free atmospheres with an amplitude of up to 10 −3 of the stellar flux, while a high-altitude cloud deck would cause a gray opacity. Aims. We observed the Saturn-mass and Jupiter-sized exoplanet HAT-P-19b to refine its transit parameters and ephemeris as well as to shed first light on its transmission spectrum. We monitored the host star over one year to quantify its flux variability and to correct the transmission spectrum for a slope caused by starspots. Methods. A transit of HAT-P-19b was observed spectroscopically with OSIRIS at the Gran Telescopio Canarias in January 2012. The spectra of the target and the comparison star covered the wavelength range from 5600 to 7600 Å. One high-precision differential light curve was created by integrating the entire spectral flux. This white-light curve was used to derive absolute transit parameters. Furthermore, a set of light curves over wavelength was formed by a flux integration in 41 wavelength channels of 50 Å width. We analyzed these spectral light curves for chromatic variations of transit depth. Results. The transit fit of the combined white-light curve yields a refined value of the planet-to-star radius ratio of 0.1390±0.0012 and an inclination of 88.89 ± 0.32 deg. After a re-analysis of published data, we refine the orbital period to 4.0087844 ± 0.0000015 days. We obtain a flat transmission spectrum without significant additional absorption at any wavelength or any slope. However, our accuracy is not sufficient to significantly rule out the presence of a pressure-broadened sodium feature. Our photometric monitoring campaign allowed for an estimate of the stellar rotation period of 35.5 ± 2.5 days and an improved age estimate of 5.5 +1.8 −1.3 Gyr by gyrochronology. The calculated correction of the transit depth for unocculted spots on the visible hemisphere was found to be well within the derived 1σ uncertainty of the white-light curve and the spectral data points of the transmission spectrum.

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Section: Introductionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 96%

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Transmission spectroscopy of the inflated exo-Saturn HAT-P-19b

Mallonn

Essen

Weingrill

et al. 2015

A&A

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“…We demonstrated the feasibility of this technique in a pilot study on WASP-6b (Jordán et al 2013), which precisely measured the optical transmission spectrum of that transiting hot Jupiter in a single transit with Magellan/IMACS, despite strongly variable transparency during part of the transit. The resulting spectrum for WASP-6b was most consistent with scattering, a result confirmed later by HST (Nikolov et al 2015;Sing et al 2016). …”

Section: Accesssupporting

confidence: 70%

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

Rackham

Espinoza

Apai

et al. 2017

ApJ

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GJ1214b is the most studied sub-Neptune exoplanet to date. Recent measurements have shown its near-infrared transmission spectrum to be flat, pointing to a high-altitude opacity source in the exoplanetʼs atmosphere, either equilibrium condensate clouds or photochemical hazes. Many photometric observations have been reported in the optical by different groups, though simultaneous measurements spanning the entire optical regime are lacking. We present an optical transmission spectrum (4500-9260Å) of GJ1214b in 14 bins, measured with Magellan/IMACS repeatedly over three transits. We measure a mean planet-to-star radius ratio of ( ) in the spectral bins. The optical transit depths are shallower on average than observed in the near-infrared. We present a model for jointly incorporating the effects of a composite photosphere and atmospheric transmission through the exoplanetʼs limb (the CPAT model), and use it to examine the cases of absorber and temperature heterogeneities in the stellar photosphere. We find the optical and near-infrared measurements are best explained by the combination of (1) photochemical haze in the exoplanetary atmosphere with a mode particle size r=0.1μm and haze-forming efficiency = f 10% haze and (2) faculae in the unocculted stellar disk with a temperature contrast D = -+ T 354 46 46 K, assuming 3.2% surface coverage. The CPAT model can be used to assess potential contributions of heterogeneous stellar photospheres to observations of exoplanet transmission spectra, which will be important for searches for spectral features in the optical.

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“…However, it is worth noting that an increase in planetary radius towards UV wavelengths has been detected for a number of planets, for instance, GJ3470b (Nascimbeni et al 2013;Biddle et al 2014), WASP-6b (Nikolov et al 2015), and WASP-31b . Interestingly, the host stars of all these planets and that of HD 189733b are active stars.…”

Section: Other Interpretations Of the Slopementioning

confidence: 99%

Using the chromatic Rossiter-McLaughlin effect to probe the broadband signature in the optical transmission spectrum of HD 189733b

Gloria

Snellen

Albrecht

2015

A&A

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Context. Transmission spectroscopy is a powerful technique for probing exoplanetary atmospheres. A successful ground-based observational method uses a differential technique that uses high-dispersion spectroscopy, but it only preserves narrow features in transmission spectra. Broadband features, such as the remarkable Rayleigh-scattering slope from possible hazes in the atmosphere of HD 189733b as observed by the Hubble Space Telescope, cannot be probed in this way. Aims. Here we use the chromatic Rossiter-McLaughlin (RM) effect to measure the Rayleigh-scattering slope in the transmission spectrum of HD 189733b with the aim to show that it can be effectively used to measure broadband transmission features. The amplitude of the RM effects depends on the effective size of the planet, and in the case of an atmospheric contribution therefore depends on the observed wavelength. Methods. We analysed archival HARPS data of three transits of HD 189733b, covering a wavelength range of 400 to 700 nm. The radial velocity (RV) time-series were determined for white light and for six wavelength bins each 50 nm wide, using the crosscorrelation profiles as provided by the HARPS data reduction pipeline. The RM effect was first fitted to the white-light RV time series using the publicly available code AROME. The residuals to this best fit were subsequently subtracted from the RV time series of each wavelength bin, after which they were also fitted using the same code, leaving only the effective planet radius to vary. Results. We measured the slope in the transmission spectrum of HD 189733b at a 2.5σ significance. Assuming it is due to Rayleigh scattering and not caused by stellar activity, it would correspond to an atmospheric temperature, as set by the scale height, of T = 2300 ± 900 K, well in line with previously obtained results. Conclusions. Ground-based high-dispersion spectral observations can be used to probe broad-band features in the transmission spectra of extrasolar planets, such as the optical Rayleigh-scattering slope of HD 189733b, by using the chromatic Rossiter-McLaughlin effect. The precision achieved with HARPS per transit is about an order of magnitude lower than that with STIS on the Hubble Space Telescope. This method will be particularly interesting in conjunction with the new echelle spectrograph ESPRESSO, which currently is under construction for ESO's Very Large Telescope, which will provide a gain in signal-to-noise ratio of about a factor 4 compared to HARPS. This will be of great value because of the limited and uncertain future of the Hubble Space Telescope and because the future James Webb Space Telescope will not cover this wavelength regime.

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HST hot-Jupiter transmission spectral survey: haze in the atmosphere of WASP-6b

Cited by 154 publications

References 80 publications

Transmission spectroscopy of the inflated exo-Saturn HAT-P-19b

Transmission spectroscopy of the inflated exo-Saturn HAT-P-19b

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

Using the chromatic Rossiter-McLaughlin effect to probe the broadband signature in the optical transmission spectrum of HD 189733b

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