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Register a new userA cool starspot or a second transiting planet in the TrES-1 system?
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We investigate the origin of a flux increase found during a transit of TrES-1, observed with the HST. This feature in the HST light curve cannot be attributed to noise and is supposedly a dark area on the stellar surface of the host star eclipsed by TrES-1 during its transit. We investigate the likeliness of two possible hypothesis for its origin: A starspot or a second transiting planet. We made use of several transit observations of TrES-1 from space with the HST and from ground with the IAC-80 telescope. On the basis of these observations we did a statistical study of flux variations in each of the observed events, to investigate if similar flux increases are present in other parts of the data set. The HST observation presents a single clear flux rise during a transit whereas the ground observations led to the detection of two such events but with low significance. In the case of having observed a starspot in the HST data, assuming a central impact between the spot and TrES-1, we would obtain a lower limit for the spot radius of 42000 km. For this radius the spot temperature would be 4690 K, 560 K lower then the stellar surface of 5250 K. For a putative second transiting planet we can set a lower limit for its radius at 0.37 R$_J$ and for periods of less than 10.5 days, we can set an upper limit at 0.72 R$_J$. Assuming a conventional interpretation, then this HST observation constitutes the detection of a starspot. Alternatively, this flux rise might also be caused by an additional transiting planet. The true nature of the origin can be revealed if a wavelength dependency of the flux rise can be shown or discarded with a higher certainty. Additionally, the presence of a second planet can also be detected by radial velocity measurements.
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We report the detection of a transiting Jupiter-sized planet orbiting a relatively bright (V=11.79) K0V star. We detected the transit light-curve signature in the course of the TrES multi-site transiting planet survey, and confirmed the planetary nature of the companion via multicolor photometry and precise radial velocity measurements. We designate the planet TrES-1; its inferred mass is 0.75 +/- 0.07 Jupiter masses, its radius is 1.08 (+0.18/-0.04) Jupiter radii, and its orbital period is 3.030065 +/- 0.000008 days. This planet has an orbital period similar to that of HD 209458b, but about twice as long as those of the OGLE transiting planets. Its mass is indistinguishable from that of HD 209458b, but its radius is significantly smaller and fits the theoretical models without the need for an additional source of heat deep in the atmosphere, as has been invoked by some investigators for HD 209458b.
We report new spectroscopic and photometric observations of the parent stars of the recently discovered transiting planets TrES-3 and TrES-4. A detailed abundance analysis based on high-resolution spectra yields [Fe/H] $= -0.19pm 0.08$, $T_mathrm{eff} = 5650pm 75$ K, and $log g = 4.4pm 0.1$ for TrES-3, and [Fe/H] $= +0.14pm 0.09$, $T_mathrm{eff} = 6200pm 75$ K, and $log g = 4.0pm0.1$ for TrES-4. The accuracy of the effective temperatures is supported by a number of independent consistency checks. The spectroscopic orbital solution for TrES-3 is improved with our new radial-velocity measurements of that system, as are the light-curve parameters for both systems based on newly acquired photometry for TrES-3 and a reanalysis of existing photometry for TrES-4. We have redetermined the stellar parameters taking advantage of the strong constraint provided by the light curves in the form of the normalized separation $a/R_star$ (related to the stellar density) in conjunction with our new temperatures and metallicities. The masses and radii we derive are $M_star=0.928_{-0.048}^{+0.028} M_{sun}$,$R_star = 0.829_{-0.022}^{+0.015} R_{sun}$, and $M_star = 1.404_{-0.134}^{+0.066} M_{sun}$, $R_star=1.846_{-0.087}^{+0.096} R_{sun}$ for TrES-3 and TrES-4, respectively. With these revised stellar parameters we obtain improved values for the planetary masses and radii. We find $M_p = 1.910_{-0.080}^{+0.075} M_mathrm{Jup}$, $R_p=1.336_{-0.036}^{+0.031} R_mathrm{Jup}$ for TrES-3, and $M_p=0.925 pm 0.082 M_mathrm{Jup}$, $R_p=1.783_{-0.086}^{+0.093} R_mathrm{Jup}$ for TrES-4. We confirm TrES-4 as the planet with the largest radius among the currently known transiting hot Jupiters.
We report the discovery and confirmation of a transiting circumbinary planet (PH1b) around KIC 4862625, an eclipsing binary in the Kepler field. The planet was discovered by volunteers searching the first six Quarters of publicly available Kepler data as part of the Planet Hunters citizen science project. Transits of the planet across the larger and brighter of the eclipsing stars are detectable by visual inspection every ~137 days, with seven transits identified in Quarters 1-11. The physical and orbital parameters of both the host stars and planet were obtained via a photometric-dynamical model, simultaneously fitting both the measured radial velocities and the Kepler light curve of KIC 4862625. The 6.18 +/- 0.17 Earth radii planet orbits outside the 20-day orbit of an eclipsing binary consisting of an F dwarf (1.734 +/- 0.044 Solar radii, 1.528 +/- 0.087 Solar masses) and M dwarf (0.378+/- 0.023 Solar radii, 0.408 +/- 0.024 Solar masses). For the planet, we find an upper mass limit of 169 Earth masses (0.531 Jupiter masses) at the 99.7% confidence level. With a radius and mass less than that of Jupiter, PH1b is well within the planetary regime. Outside the planets orbit, at ~1000 AU,a previously unknown visual binary has been identified that is likely bound to the planetary system, making this the first known case of a quadruple star system with a transiting planet.
We report the discovery of HATS-2b, the second transiting extrasolar planet detected by the HATSouth survey. HATS-2b is moving on a circular orbit around a V=13.6 mag, K-type dwarf star (GSC 6665-00236), at a separation of 0.0230 pm 0.0003 AU and with a period of 1.3541 days. The planetary parameters have been robustly determined using a simultaneous fit of the HATSouth, MPG/ESO~2.2,m/GROND, Faulkes Telescope South/Spectral transit photometry and MPG/ESO~2.2,m/FEROS, Euler~1.2,m/CORALIE, AAT~3.9,m/CYCLOPS radial-velocity measurements. HATS-2b has a mass of 1.37 pm 0.16 M_J, a radius of 1.14 pm 0.03 R_J and an equilibrium temperature of 1567 pm 30 K. The host star has a mass of 0.88 pm 0.04 M_Sun, radius of 0.89 pm 0.02 R_Sun and shows starspot activity. We characterized the stellar activity by analysing two photometric follow-up transit light curves taken with the GROND instrument, both obtained simultaneously in four optical bands (covering the wavelength range of 3860-9520 AA). The two light curves contain anomalies compatible with starspots on the photosphere of the parent star along the same transit chord.
With an equilibrium temperature of 1200 K, TrES-1 is one of the coolest hot Jupiters observed by {Spitzer}. It was also the first planet discovered by any transit survey and one of the first exoplanets from which thermal emission was directly observed. We analyzed all {Spitzer} eclipse and transit data for TrES-1 and obtained its eclipse depths and brightness temperatures in the 3.6 {micron} (0.083 % {pm} 0.024 %, 1270 {pm} 110 K), 4.5 {micron} (0.094 % {pm} 0.024 %, 1126 {pm} 90 K), 5.8 {micron} (0.162 % {pm} 0.042 %, 1205 {pm} 130 K), 8.0 {micron} (0.213 % {pm} 0.042 %, 1190 {pm} 130 K), and 16 {micron} (0.33 % {pm} 0.12 %, 1270 {pm} 310 K) bands. The eclipse depths can be explained, within 1$sigma$ errors, by a standard atmospheric model with solar abundance composition in chemical equilibrium, with or without a thermal inversion. The combined analysis of the transit, eclipse, and radial-velocity ephemerides gives an eccentricity $e = 0.033^{+0.015}_{-0.031}$, consistent with a circular orbit. Since TrES-1s eclipses have low signal-to-noise ratios, we implemented optimal photometry and differential-evolution Markov-chain Monte Carlo (MCMC) algorithms in our Photometry for Orbits, Eclipses, and Transits (POET) pipeline. Benefits include higher photometric precision and sim10 times faster MCMC convergence, with better exploration of the phase space and no manual parameter tuning.
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