The radii of giant planets, as measured from transit observations, may vary with wavelength due to Rayleigh scattering or variations in opacity. Such an effect is predicted to be large enough to detect using ground-based observations at multiple wavelengths. We present the defocused photometry of a transit in the HAT-P-5 system, obtained simultaneously through Stroemgren u, Gunn g and r, and Johnson I filters. Two more transit events were observed through a Gunn r filter.
We present z-band photometry of three consecutive transits of the exoplanet TrES-1, with an accuracy of 0.15% and a cadence of 40s. We improve on estimates of the system parameters, finding in particular that the planetary radius is 1.081+/-0.029R_Jup_ and the stellar radius is 0.011+/-0.020R_{sun}_. The uncertainties include both the statistical error and the systematic error arising from the uncertainty in the stellar mass. The transit times are determined to within about 15s and allow us to refine the estimate of the mean orbital period: P=3.0300737+/-0.0000026days. We find no evidence for starspots or other irregularities that have been previously reported.
The sub-Jovian or Neptunian desert is a previously-identified region of parameter space where there is a relative dearth of intermediate- mass planets at short orbital periods. We present the discovery of a new transiting planetary system within the Neptunian desert, NGTS-14A. Transits of NGTS-14Ab were discovered in photometry from the Next Generation Transit Survey (NGTS). Follow-up transit photometry was conducted from several ground-based facilities, as well as extracted from TESS full- frame images. We combine radial velocities from the HARPS spectrograph with the photometry in a global analysis to determine the system parameters. NGTS-14Ab has a radius about 30 per cent larger than that of Neptune (0.444+/-0.030R_Jup_), and is around 70 per cent more massive than Neptune (0.092+/-0.012 M_Jup_). It transits the main-sequence K1 star, NGTS-14A, with a period of 3.54 days, just far enough to have maintained at least some of its primordial atmosphere. We have also identified a possible long-period stellar mass companion to the system, NGTS-14B.
In 2007, the young star 1SWASP J140747.93-394542.6 (V1400 Cen) underwent a complex series of deep eclipses over 56 days. This was attributed to the transit of a ring system filling a large fraction of the Hill sphere of an unseen substellar companion. Subsequent photometric monitoring has not found any other deep transits from this candidate ring system, but if there are more substellar companions and if they are coplanar with the potential ring system, there is a chance that they will transit the star as well. This young star is active, and the light curves show a 5% modulation in amplitude with a dominant rotation period of 3.2 days due to starspots rotating into and out of view. We model and remove the rotational modulation of the J1407 light curve and search for additional transit signatures of substellar companions orbiting around J1407. We combine the photometry of J1407 from several observatories, spanning a 19 year baseline. We remove the rotational modulation by modeling the variability as a periodic signal, whose periodicity changes slowly with time over several years due to the activity cycle of the star. A transit least squares (TLS) analysis is used to search for any periodic transiting signals within the cleaned light curve. We identify an activity cycle of J1407 with a period of 5.4yr. A TLS search does not find any plausible periodic eclipses in the light curve, from 1.2% amplitude at 5 days up to 1.9% at 20 days. This sensitivity is confirmed by injecting artificial transits into the light curve and determining the recovery fraction as a function of transit depth and orbital period. J1407 is confirmed as a young active star with an activity cycle consistent with a rapidly rotating solar mass star. With the rotational modulation removed, the TLS analysis reaches down to planetary mass radii for young exoplanets, ruling out transiting companions with radii larger than about 1R_Jup_.
We present 11 high-precision photometric transit observations of the transiting super-Earth planet GJ 1214 b. Combining these data with observations from other authors, we investigate the ephemeris for possible signs of transit timing variations (TTVs) using a Bayesian approach. The observations were obtained using telescope-defocusing techniques, and achieve a high precision with random errors in the photometry as low as 1 mmag per point. To investigate the possibility of TTVs in the light curve, we calculate the overall probability of a TTV signal using Bayesian methods.
We present the first photometric follow-up of the transiting planet HAT-P-16 b, and new photometric observations of WASP-21 b, obtained simultaneously with two medium-class telescopes located in different countries, using the telescope defocussing technique. We modeled these and other published data in order to estimate the physical parameters of the two planetary systems.
We present six new transits of the exoplanet OGLE-TR-111b observed with the Magellan Telescopes in Chile between 2008 April and 2009 March. We combine these new transits with five previously published transit epochs for this planet between 2005 and 2006 to extend the analysis of transit timing variations (TTVs) reported for this system. We derive a new planetary radius value of 1.019+/-0.026R_J_, which is intermediate to the previously reported radii of 1.067+/-0.054R_J_ and 0.922+/-0.057R_J_. We also examine the TTV and duration change claims of Diaz et al. (2008ApJ...682L..49D). Our analysis of all 11 transit epochs does not reveal any points with deviations larger than 2{sigma}, and most points are well within 1{sigma}. Although the transit duration nominally decreases over the four year span of the data, systematic errors in the photometry can account for this result. Therefore, there is no compelling evidence for either a timing or a duration variation in this system. Numerical integrations place an upper limit of about 1M_{earth}_ on the mass of a potential second planet in a 2:1 mean-motion resonance with OGLE-TR-111b.
We report the results of the first transit timing variation analysis of the very hot Jupiter OGLE-TR-132b, using 10 transits collected over a seven-year period. Our analysis combines three previously published transit light curves with seven new transits, which were observed between 2008 February and 2009 May with the new MagIC-e2V instrument on the Magellan Telescopes in Chile. We provide a revised planetary radius of R_p_=1.23+/-0.07R_J_, which is slightly larger, but consistent within the errors, than that given by previously published results. Analysis of the planet-to-star radius ratio, orbital separation, inclination, and transit duration reveals no apparent variation in any of those parameters during the time span observed. We also find no sign of transit timing variations larger than -108+/-49s, with most residuals very close to zero. This allows us to place an upper limit of 5-10M_{earth}_ for a coplanar, low-eccentricity perturber in either the 2:1 or 3:2 mean-motion resonance with OGLE-TR-132b. We similarly find that the data are entirely consistent with a constant orbital period and there is no evidence for orbital decay within the limits of precision of our data.
We report the discovery of one newly confirmed planet (P=66.06 days, R_P_=2.68+/-0.17 R_{Earth}_) and mass determinations of two previously validated Kepler planets, Kepler-289 b (P=34.55 days, R_P_=2.15+/-0.10 R_{Earth}_) and Kepler-289-c (P=125.85 days, R_P_=11.59+/-0.10 R_{Earth}_), through their transit timing variations (TTVs). We also exclude the possibility that these three planets reside in a 1:2:4 Laplace resonance. The outer planet has very deep (~1.3%), high signal-to-noise transits, which puts extremely tight constraints on its host star's stellar properties via Kepler's Third Law. The star PH3 is a young (~1 Gyr as determined by isochrones and gyrochronology), Sun-like star with M_*_=1.08+/-0.02 M_{sun}_, R_*_=1.00+/-0.02 R_{sun}_, and T_eff_=5990+/-38 K. The middle planet's large TTV amplitude (~5 hr) resulted either in non-detections or inaccurate detections in previous searches. A strong chopping signal, a shorter period sinusoid in the TTVs, allows us to break the mass-eccentricity degeneracy and uniquely determine the masses of the inner, middle, and outer planets to be M=7.3+/-6.8 M_{oplus}_, 4.0+/-0.9M_{oplus}_, and M=132+/-17 M_{oplus}_, which we designate PH3 b, c, and d, respectively. Furthermore, the middle planet, PH3 c, has a relatively low density, {rho}=1.2+/-0.3 g/cm3 for a planet of its mass, requiring a substantial H/He atmosphere of 2.1_-0.3_^+0.8^% by mass, and joins a growing population of low-mass, low-density planets.
