S. C. C. Barros

Line-profile tomography of exoplanet transits - II. A gas-giant planet transiting a rapidly rotating A5 star

Most of our knowledge of extrasolar planets rests on precise radial-velocity measurements, either for direct detection or for confirmation of the planetary origin of photometric transit signals. This has limited our exploration of the parameter space of exoplanet hosts to solar- and later-type, sharp-lined stars. Here we extend the realm of stars with known planetary companions to include hot, fast-rotating stars. Planet-like transits have previously been reported in the light curve obtained by the SuperWASP survey of the A5 star HD 15082 (WASP–33; V= 8.3, v sin i= 86 km s−1). Here we report further photometry and time-series spectroscopy through three separate transits, which we use to confirm the existence of a gas-giant planet with an orbital period of 1.22 d in orbit around HD 15082. From the photometry and the properties of the planet signal travelling through the spectral line profiles during the transit, we directly derive the size of the planet, the inclination and obliquity of its orbital plane and its retrograde orbital motion relative to the spin of the star. This kind of analysis opens the way to studying the formation of planets around a whole new class of young, early-type stars, hence under different physical conditions and generally in an earlier stage of formation than in sharp-lined late-type stars. The reflex orbital motion of the star caused by the transiting planet is small, yielding an upper mass limit of 4.1 MJupiter on the planet. We also find evidence of a third body of substellar mass in the system, which may explain the unusual orbit of the transiting planet. In HD 15082, the stellar line profiles also show evidence of non-radial pulsations, clearly distinct from the planetary transit signal. This raises the intriguing possibility that tides raised by the close-in planet may excite or amplify the pulsations in such stars.

Orbital periods of cataclysmic variables identified by the SDSS - III. Time-series photometry obtained during the 2004/5 International Time Project on La Palma

We present time-resolved CCD photometry of 15 cataclysmic variables (CVs) identified by the Sloan Digital Sky Survey (SDSS). The data were obtained as part of the 2004/2005 International Time Programme on La Palma. We discuss the morphology of the light curves and the CV subtypes, and give accurate orbital periods for 11 systems. Nine systems are found below the 2-3 h orbital period gap, of which five have periods within a few minutes of the similar to 80 min minimum orbital period. One system each is found within and above the gap. This confirms the previously noted trend for a large fraction of short-period systems among the SDSS CVs. Objects of particular interest are SDSS J0901+4809 and SDSS J1250+6655 which are deeply eclipsing. SDSS J0854+3905 is a polar with an extremely modulated light curve, which is likely due to a mixture of cyclotron beaming and eclipses of the accretion region by the white dwarf. One out of five systems with white dwarf dominated optical spectra exhibits non-radial pulsations.

Geometrical constraints upon the unipolar model of V407 Vul and RXJ0806.3+1527

V407 Vul and RX J0806.3 + 1527 are X-ray emitting stars with X-ray light curves that are 100 per cent modulated on periods of 569 and 321 s, respectively. These periods and no others are also seen at optical and infrared wavelengths. These properties have led to the suggestion that the periods are the orbital periods of ultracompact pairs of white dwarfs. There are two main double white dwarf models: the unipolar inductor model analogous to the Jupiter-Io system and the direct impact model analogous to Algol. In this paper, we consider geometrical constraints on the unipolar inductor model, in particular what parameter values (component masses, orbital inclination and magnetic colatitude) can describe the X-ray and optical light curves. We find that for a dipole field on the primary star, the unipolar inductor model fails to match the data on V407 Vul for any combination of parameters and can only match RX J0806.3 + 1527 if the sparser set of observations of this star have been unluckily timed.

WASP-30b: A 61 M-Jup BROWN DWARF TRANSITING A V=12, F8 STAR

We report the discovery of a 61-Jupiter-mass brown dwarf (BD), which transits its F8V host star, WASP-30, every 4.16 days. From a range of age indicators we estimate the system age to be 1-2 Gyr. We derive a radius (0.89 ± 0.02 R Jup) for the companion that is consistent with that predicted (0.914 R Jup) by a model of a 1 Gyr old, non-irradiated BD with a dusty atmosphere. The location of WASP-30b in the minimum of the mass-radius relation is consistent with the quantitative prediction of Chabrier & Baraffe, thus confirming the theory.

SuperWASP observations of pulsating Am stars

We have studied over 1600 Am stars at a photometric precision of 1 mmag with SuperWASP photometric data. Contrary to previous belief, we find that around 200 Am stars are pulsating δ Sct and γ Dor stars, with low amplitudes that have been missed in previous, less extensive studies. While the amplitudes are generally low, the presence of pulsation in Am stars places a strong constraint on atmospheric convection, and may require the pulsation to be laminar. While some pulsating Am stars have been previously found to be δ Sct stars, the vast majority of Am stars known to pulsate are presented in this paper. They will form the basis of future statistical studies of pulsation in the presence of atomic diffusion.

WASP-30b: A 61MJupBROWN DWARF TRANSITING AV= 12, F8 STAR

We report the discovery of a 61-Jupiter-mass brown dwarf (BD), which transits its F8V host star, WASP-30, every 4.16 days. From a range of age indicators we estimate the system age to be 1-2 Gyr. We derive a radius (0.89 ± 0.02 R Jup) for the companion that is consistent with that predicted (0.914 R Jup) by a model of a 1 Gyr old, non-irradiated BD with a dusty atmosphere. The location of WASP-30b in the minimum of the mass-radius relation is consistent with the quantitative prediction of Chabrier & Baraffe, thus confirming the theory.

WASP-35b, WASP-48b and WASP-51b: Two new planets and an independent discovery of HAT-P-30b

We report the detection of WASP-35b, a planet transiting a metal-poor ([Fe/H] = ?0.15) star in the Southern hemisphere, WASP-48b, an inflated planet which may have spun-up its slightly evolved host star of 1.75 R ? in the Northern hemisphere, and the independent discovery of HAT-P-30b/WASP-51b, a new planet in the Northern hemisphere. Using WASP, RISE, Faulkes Telescope South, and TRAPPIST photometry, with CORALIE, SOPHIE, and NOT spectroscopy, we determine that WASP-35b has a mass of 0.72 ? 0.06 MJ and radius of 1.32 ? 0.05RJ , and orbits with a period of 3.16 days, WASP-48b has a mass of 0.98 ? 0.09 MJ , radius of 1.67 ? 0.10 RJ , and orbits in 2.14 days, while HAT-P-30b/WASP-51b, with an orbital period of 2.81 days, is found to have a mass of 0.76 ? 0.05 MJ and radius of 1.42 ? 0.03 RJ , agreeing with values of 0.71 ? 0.03 MJ and 1.34 ? 0.07 RJ reported for HAT-P-30b.

WASP-30b: A 61 M brown dwarf transiting a V = 12, F8 star

We report the discovery of a 61-Jupiter-mass brown dwarf (BD), which transits its F8V host star, WASP-30, every 4.16 days. From a range of age indicators we estimate the system age to be 1-2 Gyr. We derive a radius (0.89 ± 0.02 R Jup) for the companion that is consistent with that predicted (0.914 R Jup) by a model of a 1 Gyr old, non-irradiated BD with a dusty atmosphere. The location of WASP-30b in the minimum of the mass-radius relation is consistent with the quantitative prediction of Chabrier & Baraffe, thus confirming the theory.

WASP-35b, WASP-48b, and HAT-P-30b/WASP-51b: Two new planets and an independent discovery of a HAT planet

We report the detection of WASP-35b, a planet transiting a metal-poor ([Fe/H] = ?0.15) star in the Southern hemisphere, WASP-48b, an inflated planet which may have spun-up its slightly evolved host star of 1.75 R ? in the Northern hemisphere, and the independent discovery of HAT-P-30b/WASP-51b, a new planet in the Northern hemisphere. Using WASP, RISE, Faulkes Telescope South, and TRAPPIST photometry, with CORALIE, SOPHIE, and NOT spectroscopy, we determine that WASP-35b has a mass of 0.72 ? 0.06 MJ and radius of 1.32 ? 0.05RJ , and orbits with a period of 3.16 days, WASP-48b has a mass of 0.98 ? 0.09 MJ , radius of 1.67 ? 0.10 RJ , and orbits in 2.14 days, while HAT-P-30b/WASP-51b, with an orbital period of 2.81 days, is found to have a mass of 0.76 ? 0.05 MJ and radius of 1.42 ? 0.03 RJ , agreeing with values of 0.71 ? 0.03 MJ and 1.34 ? 0.07 RJ reported for HAT-P-30b.

Independent discovery of the transiting exoplanet HAT-P-14b

We present SuperWASP observations of HAT-P-14b, a hot Jupiter discovered by Torres et al. The planet was found independently by the SuperWASP team and named WASP-27b after follow-up observations had secured the discovery, but prior to the publication by Torres et al. Our analysis of HAT-P-14/WASP-27 is in good agreement with the values found by Torres et al. and we provide additional evidence against astronomical false positives. Due to the brightness of the host star, V mag = 10, HAT-P-14b is an attractive candidate for further characterization observations. The planet has a high impact parameter and the primary transit is close to grazing. This could readily reveal small deviations in the orbital parameters indicating the presence of a third body in the system, which may be causing the small but significant orbital eccentricity. Our results suggest that the planet may undergo a grazing secondary eclipse. However, even a non-detection would tightly constrain the system parameters.