A Gemini ground-based transmission spectrum of WASP-29b: a featureless spectrum from 515 to 720 nm

Gibson, Neale P.; Aigrain, S.; Barstow, Joanna K.; Evans, T. M.; Fletcher, Leigh N.; Irwin, Patrick

doi:10.1093/mnras/sts307

Cited by 137 publications

(84 citation statements)

References 31 publications

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“…Also, day-side spectral features may be absent due to an isothermal pressuretemperature profile (Fortney et al 2006). These planets are consistent with other transiting exoplanet observations with flat spectra in optical wavelengths on TrES-3b , GJ 3470b (a hot Uranus; Biddle et al 2014), GJ 1214b (Bean et al 2011;Kreidberg et al 2014), WASP-29b (Gibson et al 2013a), and HAT-P-32b (Gibson et al 2013b).…”

Section: Wavelength Dependence On the Planetary Radiussupporting

confidence: 90%

Ground-based near-UV observations of 15 transiting exoplanets: constraints on their atmospheres and no evidence for asymmetrical transits

Turner

Pearson

Biddle

et al. 2016

Mon. Not. R. Astron. Soc.

107

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Transits of exoplanets observed in the near-UV have been used to study the scattering properties of their atmospheres and possible star-planet interactions. We observed the primary transits of 15 exoplanets (CoRoT-1b, GJ436b, HAT-P-1b, HAT-P-13b, HAT-P-16b, HAT-P-22b, TrES2b, in the near-UV and several optical photometric bands to update their planetary parameters, ephemerides, search for a wavelength dependence in their transit depths to constrain their atmospheres, and determine if asymmetries are visible in their light curves. Here, we present the first ground-based near-UV light curves for 12 of the targets (CoRoT1b, GJ436b, HAT-P-1b, HAT-P-13b, HAT-P-22b, TrES-2b, TrES-4b, WASP-1b, WASP-33b, WASP-36b, WASP-48b, and WASP-77Ab). We find that none of the near-UV transits exhibit any non-spherical asymmetries, this result is consistent with recent theoretical predictions by Ben-Jaffel et al. and Turner et al. The multiwavelength photometry indicates a constant transit depth from near-UV to optical wavelengths in 10 targets (suggestive of clouds), and a varying transit depth with wavelength in 5 targets (hinting at Rayleigh or aerosol scattering in their atmospheres). We also present the first detection of a smaller near-UV transit depth than that measured in the optical in WASP-1b and a possible opacity source that can cause such radius variations is currently unknown. WASP-36b also exhibits a smaller near-UV transit depth at

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Section: Wavelength Dependence On the Planetary Radiussupporting

confidence: 90%

Ground-based near-UV observations of 15 transiting exoplanets: constraints on their atmospheres and no evidence for asymmetrical transits

Turner

Pearson

Biddle

et al. 2016

Mon. Not. R. Astron. Soc.

107

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“…The lack of pre-ingress baseline made our modeling of underlying systematics in the light curve (detrending) more error prone and hence increased our final error bars in the transmission spectrum. If follow-up observations confirm the flat transmission spectrum to higher significance, the spectrum of HAT-P-19b would share an important property with the spectra of other close-in gas giants of about 1000 K atmospheric temperature investigated so far (Gibson et al 2013a;Nikolov et al 2014;Line et al 2013): None of their transmission spectra can be explained by a cloud-or haze-free atmosphere model, they all show indications of an additional opacity source blocking parts of the probable atmosphere. …”

Section: Resultsmentioning

confidence: 87%

“…Both models were computed according to the system parameters of are three planets similar to HAT-P-19b in their system parameters: HAT-P-1b (Bakos et al 2007), HAT-P-12b (Hartman et al 2009), and WASP-29b (Hellier et al 2010). All these planets have roughly the mass of Saturn, roughly the size of Jupiter, and an equilibrium temperature of 1000 to 1200 K. They orbit solarlike main-sequence stars of spectral type G or K. Gibson et al (2013a) obtained an optical transmission spectrum of WASP29b around the sodium line and was able to significantly rule out a pressure-broadened absorption feature. Nikolov et al (2014) observed HAT-P-1b in the optical regime during transit and detected additional absorption at the sodium core in a 30 Å wide flux channel, but no spectral signature of the broadened line wings.…”

Section: Transmission Spectrummentioning

confidence: 99%

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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“…Moreover, in the last 4 years, ground-based observations have also yielded promising results (e.g. Bean et al 2010;Murgas et al 2014;Jordán et al 2013;Gibson et al 2013a). However, both space-based and groundbased data often are affected by systematic noise signals, which need to be addressed before a high quality transmission spectrum can be extracted.…”

Section: Introductionmentioning

confidence: 99%

The GTC exoplanet transit spectroscopy survey

Nortmann

Pallé

Murgas

et al. 2016

A&A

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We observed the hot Jupiter HAT-P-32b (also known as HAT-P-32Ab) to determine its optical transmission spectrum by measuring the wavelength-dependent planet-to-star radius ratios in the region between 518 -918 nm. We used the OSIRIS instrument at the GTC in long slit spectroscopy mode, placing HAT-P-32 and a reference star in the same slit and obtaining a time series of spectra covering two transit events. Using the best quality data set, we were able to yield 20 narrow-band transit light curves, with each passband spanning a 20 nm wide interval. After removal of all systematic noise signals and light curve modeling the uncertainties for the resulting radius ratios lie between 337 and 972 ppm. The radius ratios show little variation with wavelength suggesting a high altitude cloud layer masking any atmospheric features. Alternatively, a strong depletion in alkali metals or a much smaller than expected planetary atmospheric scale height could be responsible for the lack of atmospheric features. Our result of a flat transmission spectrum is consistent with a previous ground-based study of the optical spectrum of this planet. This agreement between independent results demonstrates that ground-based measurements of exoplanet atmospheres can give reliable and reproducible results despite the fact that the data often is heavily affected by systematic noise, as long as the noise source is well understood and properly corrected. We also extract an optical spectrum of the M-dwarf companion HAT-P-32B. Using PHOENIX stellar atmosphere models we determine an effective temperature of T eff = 3187 +60 −71 K, slightly colder than previous studies relying only on broadband infra-red data.

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A Gemini ground-based transmission spectrum of WASP-29b: a featureless spectrum from 515 to 720 nm

Cited by 137 publications

References 31 publications

Ground-based near-UV observations of 15 transiting exoplanets: constraints on their atmospheres and no evidence for asymmetrical transits

Ground-based near-UV observations of 15 transiting exoplanets: constraints on their atmospheres and no evidence for asymmetrical transits

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

The GTC exoplanet transit spectroscopy survey

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