We report the discovery of a sub-Jupiter mass exoplanet transiting a magnitude V=11.6 host star 1SWASP J030928.54+304024.7. ************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * announced in the paper * * * **************************************************************************
We present a new optical (400-950nm) transmission spectrum of the hot Jupiter WASP-31b (M=0.48M_Jup_; R=1.54R_Jup_; P=3.41days), obtained by combining four transit observations. These transits were observed with IMACS on the Magellan Baade Telescope at Las Campanas Observatory as part of the ACCESS project. We investigate the presence of clouds/hazes in the upper atmosphere of this planet, as well as the contribution of stellar activity on the observed features. In addition, we search for absorption features of the alkali elements NaI and KI, with particular focus on KI, for which there have been two previously published disagreeing results. Observations with Hubble Space Telescope (HST)/STIS detected KI, whereas ground-based low- and high- resolution observations did not. We use equilibrium and nonequilibrium chemistry retrievals to explore the planetary and stellar parameter space of the system with our optical data combined with existing near-IR observations. Our best-fit model is that with a scattering slope consistent with a Rayleigh slope ({alpha}=5.3_-3.1_^+2.9^), high-altitude clouds at a log cloud top pressure of -3.6_-2.1_^+2.7^bars, and possible muted H2O features. We find that our observations support other ground-based claims of no KI. Clouds are likely why signals like H2O are extremely muted and Na or K cannot be detected. We then juxtapose our Magellan/IMACS transmission spectrum with existing VLT/FORS2, HST/WFC3, HST/STIS, and Spitzer observations to further constrain the optical-to-infrared atmospheric features of the planet. We find that a steeper scattering slope ({alpha}=8.3{+/-}1.5) is anchored by STIS wavelengths blueward of 400nm and only the original STIS observations show significant potassium signal.
The TESS and PLATO missions are expected to find vast numbers of new transiting planet candidates. However, only a fraction of these candidates will be legitimate planets, and the candidate validation will require a significant amount of follow-up resources. Radial velocity (RV) follow-up study can be carried out only for the most promising candidates around bright, slowly rotating, stars. Thus, before devoting RV resources to candidates, they need to be vetted using cheaper methods, and, in the cases for which an RV confirmation is not feasible, the candidate's true nature needs to be determined based on these alternative methods alone. We study the applicability of multicolour transit photometry in the validation of transiting planet candidates when the candidate signal arises from a real astrophysical source (transiting planet, eclipsing binary, etc.), and not from an instrumental artefact. Particularly, we aim to answer how securely we can estimate the true uncontaminated star-planet radius ratio when the light curve may contain contamination from unresolved light sources inside the photometry aperture when combining multicolour transit observations with a physics-based contamination model in a Bayesian parameter estimation setting. More generally, we study how the contamination level, colour differences between the planet host and contaminant stars, transit signal-to-noise ratio, and available prior information affect the contamination and true radius ratio estimates. The study is based on simulations and ground-based multicolour transit observations. The contamination analyses were carried out with a contamination model integrated into the PYTRANSIT V2 transit modelling package, and the observations were carried out with the MuSCAT2 multicolour imager installed in the 1.5m Telescopio Carlos Sanchez in the Teide Observatory, in Tenerife. We show that multicolour transit photometry can be used to estimate the amount of flux contamination and the true radius ratio. Combining the true radius ratio with an estimate for the stellar radius yields the true absolute radius of the transiting object, which is a valuable quantity in statistical candidate validation, and enough in itself to validate a candidate whose radius falls below the theoretical lower limit for a brown dwarf.
We report the discovery by the WASP transit survey of two new highly irradiated giant planets. WASP-64 b is slightly more massive (1.271+/-0.068M_Jup_) and larger (1.271+/-0.039R_Jup_) than Jupiter, and is in very-short (a=0.02648+/-0.00024AU, P=1.5732918+/-0.0000015-days) circular orbit around a V=12.3 G7-type dwarf (1.004+/-0.028M_{sun}_, 1.058+/-0.025R_{sun}_, Teff=5500+/-150K). Its size +0.059 is typical of hot Jupiters with similar masses. WASP-72 b has also a mass a bit higher than Jupiter's (1.461-0.056M_Jup_) and orbits very close (0.03708+/-0.00050AU, P=2.2167421+/-0.0000081days) to a bright (V=9.6) and moderately evolved F7-type star (1.386+/-0.055M_{sun}_, 1.98+/-0.24R_{sun}_, Teff=6250+/-100K). Despite its extreme irradiation (~5.5x10^9^erg/s/cm^2^), WASP-72 b has a moderate size (1.27+/-0.20R_Jup_) that could suggest a significant enrichment in heavy elements. Nevertheless, the errors on its physical parameters are still too high to draw any strong inference on its internal structure or its possible peculiarity.
We present photometric light-curves of the transiting extrasolar planets WASP-39b and WASP-43b obtained with three San Pedro Martir telescopes by using the defocused photometry technique.
We report the discovery from the WASP survey of two exoplanetary systems, each consisting of a Jupiter-sized planet transiting an 11th magnitude (V) main-sequence star. WASP-104b orbits its star in 1.75d, whereas WASP-106b has the fourth-longest orbital period of any planet discovered by means of transits observed from the ground, orbiting every 9.29d. Each planet is more massive than Jupiter (WASP-104b has a mass of 1.27+/-0.05M_Jup_, while WASP-106b has a mass of 1.93+/-0.08M_Jup_). Both planets are just slightly larger than Jupiter, with radii of 1.14+/-0.04 and 1.09+/-0.04R_Jup_ for WASP-104 and WASP-106 respectively. No significant orbital eccentricity is detected in either system, and while this is not surprising in the case of the short-period WASP-104b, it is interesting in the case of WASP-106b, because many otherwise similar planets are known to have eccentric orbits.
We report the discovery of the planets WASP-20b and WASP-28b along with measurements of their sky-projected orbital obliquities. WASP-20b is an inflated, Saturn-mass planet (0.31M_Jup_; 1.46R_Jup_) in a 4.9-day, near-aligned (lambda=12.7+/-4.2{deg}) orbit around CD-24 102 (V=10.7; F9). Due to the low density of the planet and the apparent brightness of the host star, WASP-20 is a good target for atmospheric characterisation via transmission spectroscopy. WASP-28b is an inflated, Jupiter-mass planet (0.91M_Jup_; 1.21R_Jup_) in a 3.4-day, near-aligned (lambda=8+/-18{deg}) orbit around a V=12, F8 star. As intermediate-mass planets in short orbits around aged, cool stars (7^+2^_-1_Gyr and 6000+/-100K for WASP-20; 5^+3^_-2_Gyr and 6100+/-150K for WASP-28), their orbital alignment is consistent with the hypothesis that close-in giant planets are scattered into eccentric orbits with random alignments, which are then circularised and aligned with their stars' spins via tidal dissipation.
We report the discovery of four transiting hot Jupiters, WASP-147, WASP-160B, WASP-164, and WASP-165 from the WASP survey. WASP-147b is a near Saturn-mass (Mp=0.28M_J_) object with a radius of 1.11R_J_ orbiting a G4 star with a period (of 4.6d. WASP-160Bb has a mass and radius (Mp=0.28M_J_, Rp=1.09R_J_) (near-identical to WASP-147b, but is less irradiated, orbiting a metal-rich ([Fe/H]*=0.27) K0 star with a period of 3.8d. WASP-160B is part of a near equal-mass visual binary with an on-sky separation of 28.5 arcsec. WASP-164b is a more massive (Mp=2.13M_J_, Rp=1.13R_J_) hot Jupiter, orbiting a G2 star on a close-in (P=1.8d), but tidally stable orbit. WASP-165b is a classical (Mp=0.66M_J_, Rp=1.26R_J_) hot Jupiter in a 3.5d period orbit around a metal-rich ([Fe/H]*=0.33) star. WASP-147b and WASP-160Bb are promising targets for atmospheric characterization through transmission spectroscopy, while WASP-164b presents a good target for emission spectroscopy.
Transmission spectroscopy has proven to be a useful tool for the study of exoplanet atmospheres, because the absorption and scattering signatures of the atmosphere manifest themselves as variations in the planetary transit depth. Several planets have been studied with this technique, leading to the detection of a small number of elements and molecules (Na, K, H_2_O), but also revealing that many planets show flat transmission spectra consistent with the presence of opaque high-altitude clouds. We apply this technique to the Mp=0.40 M_jup_, Rp=1.20R_jup_, P=2.78d planet WASP-49b, aiming to characterize its transmission spectrum between 0.73 and 1um and search for the features of K and H_2_O. Owing to its density and temperature, the planet is predicted to possess an extended atmosphere and is thus a good target for transmission spectroscopy. Three transits of WASP-49b have been observed with the FORS2 instrument installed at the VLT/UT1 telescope at the ESO Paranal site. We used FORS2 in MXU mode with grism GRIS_600z, producing simultaneous multiwavelength transit light curves throughout the i' and z' bands. We combined these data with independent broadband photometry from the Euler and TRAPPIST telescopes to obtain a good measurement of the transit shape. Strong correlated noise structures are present in the FORS2 light curves, which are due to rotating flat-field structures that are introduced by inhomogeneities of the linear atmospheric dispersion corrector's transparency. We accounted for these structures by constructing common noise models from the residuals of light curves bearing the same noise structures and used them together with simple parametric models to infer the transmission spectrum. We present three independent transmission spectra of WASP-49b between 0.73 and 1.02um, as well as a transmission spectrum between 0.65 and 1.02um from the combined analysis of FORS2 and broadband data. The results obtained from the three individual epochs agree well. The transmission spectrum of WASP-49b is best fit by atmospheric models containing a cloud deck at pressure levels of 1mbar or lower.
We observed one transit and one occultation of the hot Jupiter WASP-43b simultaneously in the g'r'i'z'JHK bands using the GROND instrument on the MPG/ESO 2.2-meter telescope. From the transit event, we have independently derived WASP-43's system parameters with high precision, and improved the period to be 0.81347437(13) days. No significant variation in transit depths is detected, with the largest deviations coming from the i', H, and K bands. Given the observational uncertainties, the broad-band transmission spectrum can be explained by either (i) a flat featureless straight line that indicates thick clouds, (ii) synthetic spectra with absorption signatures of atomic Na/K or molecular TiO/VO that in turn indicate cloud-free atmosphere, or (iii) a Rayleigh scattering profile that indicates high-altitude hazes. From the occultation event, we detected planetary dayside thermal emission in the K-band with a flux ratio of 0.197+/-0.042%, which confirms previous detections obtained in the 2.09 micron narrow band and Ks-band. The K-band brightness temperature 1878^+108^_-116_K favors an atmosphere with poor day- to nightside heat redistribution. We also have a marginal detection in the i'-band (0.037^+0.023^_-0.021_%), which is either a false positive, a signature of non-blackbody radiation at this wavelength, or an indication of reflective hazes at high altitude.
