Investigating the physical properties of transiting hot Jupiters with the 1.5-m Kuiper Telescope

Investigating the physical properties of transiting hot Jupiters with the 1.5-m Kuiper Telescope

Authors:

Turner et al

Abstract:

We present new photometric data of 11 hot Jupiter transiting exoplanets (CoRoT-12b, HAT-P-5b, HAT-P-12b, HAT-P-33b, HAT-P-37b, WASP-2b, WASP-24b, WASP-60b, WASP-80b, WASP-103b and XO-3b) in order to update their planetary parameters and to constrain information about their atmospheres. These observations of CoRoT-12b, HAT-P-37b and WASP-60b are the first follow-up data since their discovery. Additionally, the first near-UV transits of WASP-80b and WASP-103b are presented. We compare the results of our analysis with previous work to search for transit timing variations (TTVs) and a wavelength dependence in the transit depth. TTVs may be evidence of a third body in the system, and variations in planetary radius with wavelength can help constrain the properties of the exoplanet’s atmosphere. For WASP-103b and XO-3b, we find a possible variation in the transit depths which may be evidence of scattering in their atmospheres. The B-band transit depth of HAT-P-37b is found to be smaller than its near-IR transit depth and such a variation may indicate TiO/VO absorption. These variations are detected from 2–4.6σ, so follow-up observations are needed to confirm these results. Additionally, a flat spectrum across optical wavelengths is found for five of the planets (HAT-P-5b, HAT-P-12b, WASP-2b, WASP-24b and WASP-80b), suggestive that clouds may be present in their atmospheres. We calculate a refined orbital period and ephemeris for all the targets, which will help with future observations. No TTVs are seen in our analysis with the exception of WASP-80b and follow-up observations are needed to confirm this possible detection.

Near-IR Emission Spectrum of hot Jupiter WASP-103b

Near-IR Emission Spectrum of WASP-103b using Hubble Space Telescope/Wide Field Camera 3

Authors:

Cartier et al

Abstract:

We present here our observations and analysis of the dayside emission spectrum of the hot Jupiter WASP-103b. We observed WASP-103b during secondary eclipse using two visits of the Hubble Space Telescope with the G141 grism on Wide Field Camera 3 in spatial scan mode. We generated secondary eclipse light curves of the planet in both blended white-light and spectrally binned wavechannels from 1.1-1.7 micron and corrected the light curves for flux contamination from a nearby companion star. We modeled the detector systematics and secondary eclipse spectrum using Gaussian process regression and found that the near-IR emission spectrum of WASP-103b is featureless across the observed near-IR region to down to a sensitivity of 175 ppm, and shows a shallow slope towards the red. The atmosphere has a single brightness temperature of T_B = 2890 K across this wavelength range. This region of the spectrum is indistinguishable from isothermal, but may not manifest from a physically isothermal system, i.e. pseudo-isothermal. A Solar-metallicity profile with a thermal inversion layer at 10^-2 bar fits WASP-103b's spectrum with high confidence, as do an isothermal profile with Solar metallicity and a monotonically decreasing atmosphere with C/O>1. The data rule out a monotonically decreasing atmospheric profile with Solar composition, and we rule out a low-metallicity decreasing profile as non-physical for this system. The pseudo-isothermal profile could be explained by a thermal inversion layer just above the layer probed by our observations, or by clouds or haze in the upper atmosphere. Transmission spectra at optical wavelengths would allow us to better differentiate between potential atmospheric models.

Hot Jupiter WASP-103b Really Does Have an Anomalous Transmission Spectrum

Contamination from a nearby star cannot explain the anomalous transmission spectrum of the ultra-short period giant planet WASP-103b

Authors:

Southworth et al

Abstract:

The planet in the WASP-103 system is an excellent candidate for transmission spectroscopy because of its large radius and high temperature. Application of this technique found a variation of radius with wavelength which was far too strong to be explained by scattering processes in the planetary atmosphere. A faint nearby star was subsequently detected, whose contamination of the transit light curves might explain this anomaly. We present a reanalysis of published data in order to characterise the faint star and assess its effect on the measured transmission spectrum. The faint star has a mass of 0.72 +/- 0.08 Msun and is almost certainly gravitationally bound to the planetary system. We find that its effect on the measured physical properties of the planet and host star is small, amounting to a planetary radius larger by 0.6 sigma and planetary density smaller by 0.8 sigma. Its influence on the measured transmission spectrum is much greater: the spectrum now has a minimum around 760 nm and opacity rises to both bluer and redder wavelengths. It is a poor match to theoretical spectra and the spectral slope remains too strong for Rayleigh scattering. The existence of the faint nearby star cannot therefore explain the measured spectral properties of this hot and inflated planet. We advocate further observations of the system, both with high spatial resolution in order to improve the measured properties of the faint star, and with higher spectral resolution to confirm the anomalous transmission spectrum of the planet.

Spin-orbit alignments for Three Transiting Hot Jupiters: WASP-103b, WASP-87b, & WASP-66b

Spin-orbit alignments for Three Transiting Hot Jupiters: WASP-103b, WASP-87b, & WASP-66b

Authors:

Addison et al

Abstract:

We have measured the sky-projected spin-orbit alignments for three transiting Hot Jupiters, WASP-103b, WASP-87b, and WASP-66b, using spectroscopic measurements of the Rossiter-McLaughlin effect, with the CYCLOPS2 optical-fiber bundle system feeding the UCLES spectrograph on the Anglo-Australian Telescope. The resulting sky projected spin-orbit angles of λ=3∘±33∘, λ=−8∘±11∘, and λ=−4∘±22∘ for WASP-103b, WASP-87b, and WASP-66b, respectively, suggest that these three planets are likely on nearly aligned orbits with respect to their host star's spin axis. WASP-103 is a particularly interesting system as its orbital distance is only 20% larger than its host star's Roche radius and the planet likely experiences strong tidal effects. WASP-87 and WASP-66 are hot (Teff=6450±120 K and Teff=6600±150 K, respectively) mid-F stars making them similar to the majority of stars hosting planets on high obliquity orbits. Moderate spin-orbit misalignments for WASP-103b and WASP-66b are consistent with our data, but polar and retrograde orbits are not favored for these systems.

Looking for a Second Star for Exoplanetary Systems

A Lucky Imaging search for stellar sources near 74 transit hosts

Authors:

Wöllert et al

Abstract:

Many transiting planet host stars lack high resolution imaging and thus close stellar sources can be missed. Those unknown stars potentially bias the derivation of the planetary and stellar parameters from the transit light curve, no matter if they are bound or not. In addition, bound stellar companions interact gravitationally with the exoplanet host star, the disk and the planets and can thus influence the formation and evolution of the planetary system strongly. We extended our high-resolution Lucky Imaging survey for close stellar sources by 74 transiting planet host stars. 39 of these stars lack previous high-resolution imaging, 23 are follow up observations of companions or companion candidates, and the remaining stars have been observed by others with AO imaging though in different bands. We determine the separation of all new and known companion candidates and estimate the flux ratio in the observed bands. All observations were carried out with the Lucky Imaging camera AstraLux Norte at the Calar Alto 2.2 m telescope in i' and z' passbands. We find new stellar sources within 1 arcsec to HAT-P-27, HAT-P-28, HAT-P-35, WASP-76, and WASP-103, and between 1 and 4 arcsec to HAT-P-29 and WASP-56.

High-precision Photometry of Hot Jupiter WASP-103

High-precision photometry by telescope defocussing. VII. The ultra-short period planet WASP-103

Authors:

Southworth et al

Abstract:

We present 17 transit light curves of the ultra-short period planetary system WASP-103, a strong candidate for the detection of tidally-induced orbital decay. We use these to establish a high-precision reference epoch for transit timing studies. The time of the reference transit midpoint is now measured to an accuracy of 4.8s, versus 67.4s in the discovery paper, aiding future searches for orbital decay. With the help of published spectroscopic measurements and theoretical stellar models, we determine the physical properties of the system to high precision and present a detailed error budget for these calculations. The planet has a Roche lobe filling factor of 0.58, leading to a significant asphericity; we correct its measured mass and mean density for this phenomenon. A high-resolution Lucky Imaging observation shows no evidence for faint stars close enough to contaminate the point spread function of WASP-103. Our data were obtained in the Bessell RI and the SDSS griz passbands and yield a larger planet radius at bluer optical wavelengths, to a confidence level of 7.3 sigma. Interpreting this as an effect of Rayleigh scattering in the planetary atmosphere leads to a measurement of the planetary mass which is too small by a factor of five, implying that Rayleigh scattering is not the main cause of the variation of radius with wavelength.

WASP-103b: a new Planet on the Cusp of Tidal Disruption

WASP-103b: a new planet at the edge of tidal disruption

Authors:

Gillon et al

Abstract:

We report the discovery of WASP-103b, a new ultra-short-period planet (P=22.2 hr) transiting a 12.1 V-magnitude F8-type main-sequence star (1.22+-0.04 Msun, 1.44-0.03+0.05 Rsun, Teff = 6110+-160 K). WASP-103b is significantly more massive (1.49+-0.09 Mjup) and larger (1.53-0.07+0.05 Rjup) than Jupiter. Its large size and extreme irradiation (around 9 10^9 erg/s/cm^2) make it an exquisite target for a thorough atmospheric characterization with existing facilities. Furthermore, its orbital distance is less than 20% larger than its Roche radius, meaning that it might be significantly distorted by tides and might experience mass loss through Roche-lobe overflow. It thus represents a new key object for understanding the last stage of the tidal evolution of hot Jupiters.