Observations and modeling of the transiting exoplanets XO-2b, HAT-P-18b, and WASP-80b (original) (raw)
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New observations and transit solutions of the exoplanets HAT-P-54b and WASP-153b
Serbian Astronomical Journal, 2019
We present photometric observations of the newly-discovered transiting exoplanets HAT-P-54b and WASP-153b with the Rozhen 2 m telescope. As a result we improved their periods. The modeling of the new transits led to almost identical values of orbital inclinations and stellar radii to the first published values while the planet radii were slightly different: that of HAT-P-54b was bigger and that of WASP-153b was smaller. The more bloated nature of WASP-153b is a result of its considerable close orbit and high stellar temperature. Our calculation of the WASP-153 distance is very close to that measured by GAIA. The best fits of the newly-observed transits of HAT-P-54b and WASP-153b correspond to the quadratic limb-darkening law of their host stars whose coefficients were determined. Our results confirmed the hot Jupiter nature of the two targets.
The Transit Light Curve Project. XII. Six Transits of the Exoplanet XO-2b
Astronomical Journal, 2009
We present photometry of six transits of the exoplanet XO-2b. By combining the light-curve analysis with theoretical isochrones to determine the stellar properties, we find the planetary radius to be 0.996 +0.031/-0.018 rjup and the planetary mass to be 0.565 +/- 0.054 mjup. These results are consistent with those reported previously, and are also consistent with theoretical models for gas giant planets. The mid-transit times are accurate to within 1 min and are consistent with a constant period. However, the period we derive differs by 2.5 sigma from the previously published period. More data are needed to tell whether the period is actually variable (as it would be in the presence of an additional body) or if the timing errors have been underestimated.
Photometry and Transit Modeling of Exoplanet XO-1b
CCD images of transits by the exoplanet XO-1b over the years 2018 to 2021 are analyzed. The data were collected by a MicroObservatory telescope in Arizona. These are supplemented by analysis of TESS space telescope data along with transits observed by amateur astronomers, leading to an investigation of the mid-transit times and the orbital period of the exoplanet. No evidence is found to support transit timing variations, with a period of 3.9415049 ± 0.0000008 days being sufficient to explain mid-transit times over 2006 to 2021. Using TESS data, the orbital radius is estimated to be some 11.10 ± 0.15 times the radius of the host star, and the planetary radius 0.1300 ± 0.0016 times the stellar radius. A simple transit model is combined with Bayesian sampling to provide estimates for the orbital inclination, radii, and limb darkening, however these estimates are not internally consistent. This is likely due to the application of the "small planet approximation," which neglects a radial gradient in the stellar flux obscured by the planet (due to the limb darkening effect), together with the model not accounting for variation in the stellar flux.
Observations of transits of the southern exoplanets WASP 4b and WASP 46b by using a 40 cm telescope
2015
We present photometric observations of transits of the southern exoplanets WASP 4b and WASP 46b using a 40 cm telescope. The obtained values of the orbital inclination, relative stellar radius and relative planet radius are well within the ranges of the previous solutions of the targets. The only exception is the bigger planet radius of WASP 4b that was necessary to reproduce the deeper transit observed by the TriG filter. Our data have a good time resolution and may be used for refinement of the ephemerides of WASP 4b and WASP 46b. The presented results confirmed that small telescopes can be used successfully for the study of exoplanets orbiting stars brighter than 13 mag.
The Transit Light Curve Project. I. Four Consecutive Transits of the Exoplanet XO‐1b
The Astrophysical Journal, 2006
We present RIz photometry of four consecutive transits of the newly discovered exoplanet XO-1b. We improve on the estimates of the transit parameters, finding the planetary radius to be R P ¼ 1:184 þ0:028 À0:018 R J , and the stellar radius to be R ? ¼ 0:928 þ0:018 À0:013 R , assuming a stellar mass of M ? ¼ (1:00 AE 0:03) M. The uncertainties in the planetary and stellar radii are dominated by the uncertainty in the stellar mass. These uncertainties increase by a factor of 2Y3 if a more conservative uncertainty of 0:10 M is assumed for the stellar mass. Our estimate of the planetary radius is smaller than that reported by McCullough and coworkers, and the resulting estimate for the mean density of XO-1b is intermediate between that of the low-density planet HD 209458b and the higher density planets TrES-1 and HD 189733b. The timings of the transits have an accuracy ranging from 0.2 to 2.5 minutes and are marginally consistent with a uniform period.
The Transit Light Curve (TLC) Project. I. Four Consecutive Transits of the Exoplanet XO-1b
2006
We present RIz photometry of four consecutive transits of the newly discovered exoplanet XO-1b. We improve upon the estimates of the transit parameters, finding the planetary radius to be R P = 1.184 +0.028 −0.018 R Jup , and the stellar radius to be R S = 0.928 +0.018 −0.013 R ⊙ , assuming a stellar mass of M S = 1.00 ± 0.03 M ⊙ . The uncertainties in the planetary and stellar radii are dominated by the uncertainty in the stellar mass. These uncertainties increase by a factor of 2-3 if a more conservative uncertainty of 0.10 M ⊙ is assumed for the stellar mass. Our estimate of the planetary radius is smaller than that reported by and yields a mean density that is comparable to that of TrES-1 and HD 189733b. The timings of the transits have an accuracy ranging from 0.2 to 2.5 minutes, and are marginally consistent with a uniform period.
The Transit Light Curve Project. IX. Evidence for a Smaller Radius of the Exoplanet XO‐3b
The Astrophysical Journal, 2008
We present photometry of 13 transits of XO-3b, a massive transiting planet on an eccentric orbit. Previous data led to two inconsistent estimates of the planetary radius. Our data strongly favor the smaller radius, with increased precision: R p = 1.217 ± 0.073 R Jup . A conflict remains between the mean stellar density determined from the light curve, and the stellar surface gravity determined from the shapes of spectral lines. We argue the light curve should take precedence, and revise the system parameters accordingly. The planetary radius is about 1σ larger than the theoretical radius for a hydrogen-helium planet of the given mass and insolation. To help in planning future observations, we provide refined transit and occultation ephemerides.
The Astrophysical Journal, 2011
As part of the NASA EPOXI Mission of Opportunity, we observed seven known transiting extrasolar planet systems in order to construct time series photometry of extremely high phase coverage and precision. Here we present the results for four "hot-Jupiter systems" with near-solar stars-HAT-P-4, TrES-3, TrES-2 and WASP-3. We observe ten transits of HAT-P-4, estimating the planet radius R p = 1.332 ± 0.052 R Jup , the stellar radius R ⋆ = 1.602 ± 0.061 R ⊙ , the inclination i = 89.67 ± 0.30 degrees and the transit duration from first to fourth contact τ = 255.6 ± 1.9 minutes. For TrES-3, we observe seven transits, and find R p = 1.320 ± 0.057 R Jup , R ⋆ = 0.817 ± 0.022 R ⊙ , i = 81.99±0.30 degrees and τ = 81.9±1.1 minutes. We also note a long term variability in the TrES-3 light curve, which may be due to star spots. We observe nine transits of
Exoplanet transits observed at UNI's Astronomical Observatory
TECNIA
This work present the exoplanet transit program developed at OAUNI on the 2016 and 2017 campaigns. Seventeen exoplanet transits were observed and in six of them more than one event was registered. In a couple of cases the same transit were gathered four times. Preliminary reductions are shown in three transits (WASP-80 b, WASP-52 b, and WASP-77 A b). The associated light curves show well-defined events and their modeling let to infer physical parameters of each system. These measurements are the first ones of their kind collected by a peruvian astronomical facility.
Ground-based transit observations of the HAT-P-18, HAT-P-19, HAT-P-27/WASP40 and WASP-21 systems
Monthly Notices of the Royal Astronomical Society, 2015
As part of our ongoing effort to investigate transit timing variations (TTVs) of known exoplanets, we monitored transits of the four exoplanets HAT-P-18b, HAT-P-19b, HAT-P-27b/WASP-40b and WASP-21b. All of them are suspected to show TTVs due to the known properties of their host systems based on the respective discovery papers. During the past three years 46 transit observations were carried out, mostly using telescopes of the Young Exoplanet Transit Initiative. The analyses are used to refine the systems' orbital parameters. In all cases we found no hints for significant TTVs, or changes in the system parameters inclination, fractional stellar radius and planet-to-star radius ratio. However, comparing our results with those available in the literature shows that we can confirm the already published values.