The extrasolar planet HAT-P-8 b was thought to be one of the more inflated transiting hot Jupiters. Aims. By using new and existing photometric data, we computed precise estimates of the physical properties of the system. Methods. We present photometric observations comprising eleven light curves covering six transit events, obtained using five medium-class telescopes and telescope-defocussing technique. One transit was simultaneously obtained through four optical filters, and two transits were followed contemporaneously from two observatories. We modelled these and seven published datasets using the jktebop code. The physical parameters of the system were obtained from these results and from published spectroscopic measurements. In addition, we investigated the theoretically-predicted variation of the apparent planetary radius as a function of wavelength, covering the range 330-960nm. Results. We find that HAT-P-8 b has a significantly lower radius (1.321R_Jup_) and mass (1.275M_Jup_) compared to previous estimates (1.50R_Jup_ and 1.52M_Jup_ respectively). We also detect a radius variation in the optical bands that, when compared with synthetic spectra of the planet, may indicate the presence of a strong optical absorber, perhaps TiO and VO gases, near the terminator of HAT-P-8 b. Conclusions. These new results imply that HAT-P-8 b is not significantly inflated, and that its position in the planetary mass-radius diagram is congruent with those of many other transiting extrasolar planets.
TASTE (The Asiago Search for Transit timing variations of Exoplanets) project is collecting high-precision, short-cadence light curves for a selected sample of transiting exoplanets. It has been claimed that the hot jupiter HAT-P-13b suddenly deviated from a linear ephemeris by ~20min, implying that there is a perturber in the system. Using five new transits, we discuss the plausibility of this transit time variation (TTV), and show that a periodic signal should not be excluded. More follow-up observations are required to constrain the mass and the orbit of the hypothetical perturber.
A promising method for detecting earth-sized exoplanets is the timing analysis of a known transit. The technique allows a search for variations in either the transit duration or the center induced by the perturbation of a third body, e.g. a second planet or an exomoon. By applying this method, the TASTE (The Asiago Search for Transit Timing variations of Exoplanets) project will collect high- precision, short-cadence light curves for a selected sample of transits by using imaging differential photometry at the Asiago 1.82m telescope. The first light curves show that our project can achieve a competitive timing accuracy, as well as a significant improvement of the orbital parameters. We derived refined ephemerides for HAT-P-3b and HAT-P-14b with a timing accuracy of 11 and 25s, respectively.
The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We report on 11 secondary-eclipse events at 3.6, 4.5, 3x5.8, 4x8.0, and 2x16{mu}m plus three primary-transit events at 8.0{mu}m. The eclipse depths from jointly fit models at each wavelength are 0.040%+/-0.003% at 3.6{mu}m, 0.034%+/-0.006% at 4.5{mu}m, 0.044%+/-0.010% at 5.8{mu}m, 0.052%+/-0.006% at 8.0{mu}m, and 0.085%+/-0.032% at 16{mu}m. Multiple observations at the longer wavelengths improved eclipse-depth signal-to-noise ratios by up to a factor of two and improved estimates of the planet-to-star radius ratio (R_p_/R_{sstarf}_=0.0518+/-0.0006). We also identify no significant deviations from a circular orbit and, using this model, report an improved period of 2.8758916+/-0.0000014 days. Chemical-equilibrium models find no indication of a temperature inversion in the dayside atmosphere of HD 149026b. Our best-fit model favors large amounts of CO and CO_2_, moderate heat redistribution (f=0.5), and a strongly enhanced metallicity. These analyses use BiLinearly-Interpolated Subpixel Sensitivity (BLISS) mapping, a new technique to model two position-dependent systematics (intrapixel variability and pixelation) by mapping the pixel surface at high resolution. BLISS mapping outperforms previous methods in both speed and goodness of fit. We also present an orthogonalization technique for linearly correlated parameters that accelerates the convergence of Markov chains that employ the Metropolis random walk sampler.
Our differential BV photometric observations, acquired with an automated telescope at Fairborn Observatory, show that HD 71636 is an eclipsing binary. From follow-up red-wavelength spectroscopic observations we classify the primary and secondary as an F2 dwarf and an F5 dwarf, respectively. The system has a period of 5.01329 days and a circular orbit. We used the Wilson-Devinney program to simultaneously solve our BV light curves and radial velocities and determined a number of fundamental properties of the system. Comparison with evolutionary tracks indicates that both stars are well ensconced on the main sequence. The age of the system is about 1.2 billion years.
We analyze new multicolor light curves for four close late-type binaries: HS Aqr, EG Cep, VW LMi, and DU Boo, in order to determine the orbital and physical parameters of the systems and estimate the distances. The analysis is done using the modeling code of G. Djurasevic, and is based on up-to-date measurements of spectroscopic elements. All four systems have complex, asymmetric light curves that we model by including bright or dark spots on one or both components. Our findings indicate that HS Aqr and EG Cep are in semi-detached, while VW LMi and DU Boo are in overcontact configurations.
We present detailed optical photometry for 25 Type Ibc supernovae (SNe Ibc) within d~150Mpc obtained with the robotic Palomar 60 inch telescope in 2004-2007. This study represents the first uniform, systematic, and statistical sample of multi-band SNe Ibc light curves available to date. We correct the light curves for host galaxy extinction using a new technique based on the photometric color evolution, namely, we show that the (V-R) color of extinction-corrected SNe Ibc at {Delta}t~10days after V-band maximum is tightly distributed, <(V-R)_V10_>=0.26+/-0.06mag. Using this technique, we find that SNe Ibc typically suffer from significant host galaxy extinction, <E(B-V)>~0.4mag. A comparison of the extinction-corrected light curves for helium-rich (Type Ib) and helium-poor (Type Ic) SNe reveals that they are statistically indistinguishable, both in luminosity and decline rate. We report peak absolute magnitudes of <M_R_>=-17.9+/-0.9 mag and <M_R_>=-18.3+/-0.6mag for SNe Ib and Ic, respectively.
We present 81 photometric lightcurve of 36 minor planets observed in the V and B bands at the ESO 50cm telescope at La Silla (Chile). These asteroids were selected preferentially in order to improve their ecliptic longitude coverage in view of pole determinations and lightcurve inversions. We also give some first photometric observations and/or rotational period for several asteroids.
We present the results of a 5.5-yr CCD photometric campaign that monitored 261 bright, southern, semiregular variables (SRVs) with relatively precise Hipparcos parallaxes. The data are supplemented with independent photoelectric observations of 34 of the brightest stars, including 11 that were not part of the CCD survey, and a previously unpublished long time- series of VZ Cam. Pulsation periods and amplitudes are established for 247 of these stars, the majority of which have not been determined before. All M giants with sufficient observations for period determination are found to be variable, with 87 per cent of the sample (at a signal-to-noise ratio of >=7.5) exhibiting multiperiodic behaviour. The period ratios of local SRVs are in excellent agreement with those in the Large Magellanic Cloud. Apparent K-band magnitudes are extracted from multiple near-infrared catalogues and analysed to determine the most reliable values. We review the effects of interstellar and circumstellar extinction and calculate absolute K-band magnitudes using revised Hipparcos parallaxes.
