I. Bruni

A lower radius and mass for the transiting extrasolar planet HAT-P-8b

Context. 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 mediumclass 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 330–960 nm. Results. We find that HAT-P-8 b has a significantly lower radius (1.321 ± 0.037RJup )a nd mass (1.275 ± 0.053 MJup) compared to previous estimates (1.50 +0.08 −0.06 RJup and 1.52 +0.18 −0.16 MJup 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.

High-precision photometry by telescope defocusing - III. The transiting planetary system WASP-2★: High-precision defocused photometry of WASP-2

We present high-precision photometry of three transits of t he extrasolar planetary system WASP-2, obtained by defocussing the telescope, and achievi ng point-to-point scatters of between 0.42 and 0.73 mmag. These data are modelled using the JKTEBOP code, and taking into account the light from the recently-discovered faint s tar close to the system. The physical properties of the WASP-2 system are derived using tabulated pr ictions from five different sets of stellar evolutionary models, allowing both statist ical and systematic errorbars to be specified. We find the mass and radius of the planet to be M = 0.847± 0.038± 0.024MJup andRb = 1.044± 0.029± 0.015RJup. It has a low equilibrium temperature of 1280± 21K, in agreement with a recent finding that it does not have an atmo spheric temperature inversion. The first of our transit datasets has a scatter of only 0.42 mma g with respect to the best-fitting light curve model, which to our knowledge is a record for grou nd-based observations of a transiting extrasolar planet.

The GAPS Programme with HARPS-N at TNG ,, VIII. Observations of the Rossiter-McLaughlin effect and characterisation of the transiting planetary systems HAT-P-36 and WASP-11/HAT-P-10

We determine the true and the projected obliquity of HAT-P-36 and WASP-11/HAT-P-10 systems, respectively, which are both composed of a relatively cool star and a hot-Jupiter planet. Thanks to the high-resolution spectrograph HARPS-N, we observed the Rossiter-McLaughlin effect for both the systems by acquiring precise radial-velocity measurements during planetary transit events. We also present photometric observations comprising six light curves covering five transit events, obtained using three medium-class telescopes and the telescope-defocussing technique. One transit of WASP-11/HAT-P-10 was followed simultaneously from two observatories. The three transit light curves of HAT-P-36b show anomalies that are attributable to starspot complexes on the surface of the parent star, in agreement with the analysis of its spectra that indicate a moderate activity. By analysing the complete HATNet data set of HAT-P-36, we estimated the stellar rotation period by detecting a periodic photometric modulation in the light curve caused by star spots, obtaining Prot=15.3 days, which implies that the inclination of the stellar rotational axis with respect to the line of sight is 65 degree. We used the new spectroscopic and photometric data to revise the main physical parameters and measure the sky-projected misalignment angle of the two systems. We found \lambda=-14 degree for HAT-P-36 and \lambda=7 degree for WASP-11/HAT-P-10, indicating in both cases a good spin-orbit alignment. In the case of HAT-P-36, we also measured its real obliquity, which turned out to be 25 degrees.

Simultaneous follow-up of planetary transits: revised physical properties for the planetary systems HAT-P-16 and WASP-21

Context. By now, more than 300 planets transiting their host star have been found, and much effort is being put into measuring the properties of each system. Light curves of planetary transits often contain deviations from a simple transit shape, and it is generally difficult to differentiate between anomalies of astrophysical nature (e.g. starspots) and correlated noise due to instrumental or atmospheric effects. Our solution is to observe transit events simultaneously with two telescopes located at different observatories. Aims. Using this observational strategy, we look for anomalies in the light curves of two transiting planetary systems and accurately estimate their physical parameters. 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 defocusing technique. We modeled these and other published data in order to estimate the physical parameters of the two planetary systems. Results. The simultaneous observations did not highlight particular features in the light curves, which is consistent with the low activity levels of the two stars. For HAT-P-16, we calculated a new ephemeris and found that the planet is 1.3σ colder and smaller (Rb = 1.190 ± 0.037 RJup) than the initial estimates, suggesting the presence of a massive core. Our physical parameters for this system point toward a younger age than previously thought. The results obtained for WASP-21 reveal lower values for the mass and the density of the planet (by 1.0 and 1.4σ respectively) with respect to those found in the discovery paper, in agreement with a subsequent study. We found no evidence of any transit timing variations in either system.

Two new ZZ Ceti pulsators from the HS and HE surveys

We report the detection of nonradial g-mode oscillations in the DA white dwarfs HS 1039+4112 (B=15.9) and HE 1429 0343 (B=15.8) from time-series photometry made at the Loiano 1.5 m telescope. The two stars were previously selected as probable pulsators based on two-color photometry and spectral analysis respectively. Following our temperature and surface gravity determinations, HS 1039+4112 (Teff=11200 K, log g=8.2) is located near the red edge of the ZZ Ceti instability strip, whereas HE 1429 0343 (Teff=11400 K, log g=7.8) falls in the middle of the strip. Both stars show a multi- mode behavior with the main periods at about 850 and 970 s respectively, and relatively large amplitudes (�7% and�2.5%).

Physical properties of the HAT-P-23 and WASP-48 planetary systems from multi-colour photometry

Accurate and repeated photometric follow-up observations of planetary-transit events are important to precisely characterize the physical properties of exoplanets. A good knowledge of the main characteristics of the exoplanets is fundamental to trace their origin and evolution. Multi-band photometric observations play an important role in this process. By using new photometric data, we computed precise estimates of the physical properties of two transiting planetary systems. We present new broad-band, multi-colour, photometric observations obtained using three small class telescopes and the telescope-defocussing technique. For each of the two targets, one transit event was simultaneously observed through four optical filters. One transit of WASP-48 b was monitored with two telescopes from the same observatory. The physical parameters of the systems were obtained by fitting the transit light curves with {\sc jktebop} and from published spectroscopic measurements. We have revised the physical parameters of the two planetary systems, finding a smaller radius for both HAT-P-23 b and WASP-48 b,

High-precision multiband time series photometry of exoplanets Qatar-1b and TrES-5b

R_{b}=1.224 \pm 0.037 R_{Jup}

A New Fast Silicon Photomultiplier Photometer

and

Orbital alignment and star-spot properties in the WASP-52 planetary system

R_{b}=1.396 \pm 0.051 \, R_{Jup}

Red-channel (6000−8000 Å) nuclear spectra of 376 local galaxies

, respectively, than those measured in the discovery papers (