D. J. Christian

The WASP Project and the SuperWASP Cameras

ABSTRACT The SuperWASP cameras are wide‐field imaging systems at the Observatorio del Roque de los Muchachos on the island of La Palma in the Canary Islands, and at the Sutherland Station of the South African Astronomical Observatory. Each instrument has a field of view of some 482 deg2 with an angular scale of 13 \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Alfvén Waves in the Lower Solar Atmosphere

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WASP-12b: The Hottest Transiting Extrasolar Planet Yet Discovered

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WASP-1b and WASP-2b: two new transiting exoplanets detected with SuperWASP and SOPHIE

The flow of energy through the solar atmosphere and the heating of the Suns outer regions are still not understood. Here, we report the detection of oscillatory phenomena associated with a large bright-point group that is 430,000 square kilometers in area and located near the solar disk center. Wavelet analysis reveals full-width half-maximum oscillations with periodicities ranging from 126 to 700 seconds originating above the bright point and significance levels exceeding 99%. These oscillations, 2.6 kilometers per second in amplitude, are coupled with chromospheric line-of-sight Doppler velocities with an average blue shift of 23 kilometers per second. A lack of cospatial intensity oscillations and transversal displacements rules out the presence of magneto-acoustic wave modes. The oscillations are a signature of Alfvén waves produced by a torsional twist of ±22 degrees. A phase shift of 180 degrees across the diameter of the bright point suggests that these torsional Alfvén oscillations are induced globally throughout the entire brightening. The energy flux associated with this wave mode is sufficient to heat the solar corona.

WASP-3b: a strongly irradiated transiting gas-giant planet

We report on the discovery of WASP-12b, a new transiting extrasolar planet with R pl = 1.79+0.09 –0.09 RJ and M pl = 1.41+0.10 –0.10 M J. The planet and host star properties were derived from a Monte Carlo Markov Chain analysis of the transit photometry and radial velocity data. Furthermore, by comparing the stellar spectrum with theoretical spectra and stellar evolution models, we determined that the host star is a supersolar metallicity ([M/H] = 0.3+0.05 –0.15), late-F (T eff = 6300+200 –100 K) star which is evolving off the zero-age main sequence. The planet has an equilibrium temperature of T eq = 2516 K caused by its very short period orbit (P = 1.09 days) around the hot, twelfth magnitude host star. WASP-12b has the largest radius of any transiting planet yet detected. It is also the most heavily irradiated and the shortest period planet in the literature.

WASP-12b: The hottest transiting extrasolar planet yet discovered

We have detected low-amplitude radial-velocity variations in two stars, USNO-B1.0 1219‐ 0005465 (GSC 02265‐00107 = WASP‐1) and USNO-B1.0 0964‐0543604 (GSC 00522‐ 01199 = WASP‐2). Both stars were identified as being likely host stars of transiting exoplanets in the 2004 SuperWASP wide-field transit survey. Using the newly commissioned radial-velocity spectrograph SOPHIE at the Observatoire de Haute-Provence, we found that both objects exhibit reflex orbital radial-velocity variations with amplitudes characteristic of planetary-mass companions and in-phase with the photometric orbits. Line-bisector studies rule out faint blended binaries as the cause of either the radial-velocity variations or the transits. We perform preliminary spectral analyses of the host stars, which together with their radialvelocity variations and fits to the transit light curves yield estimates of the planetary masses and radii. WASP-1b and WASP-2b have orbital periods of 2.52 and 2.15 d, respectively. Given mass estimates for their F7V and K1V primaries, we derive planet masses 0.80‐0.98 and 0.81‐ 0.95 times that of Jupiter, respectively. WASP-1b appears to have an inflated radius of at least 1.33 RJup, whereas WASP-2b has a radius in the range 0.65‐1.26 RJup.

A fast hybrid algorithm for exoplanetary transit searches

We report the discovery of WASP-3b, the third transiting exoplanet to be discovered by the WASP and SOPHIE collaboration. WASP-3b transits its host star USNO-B1.0 1256−0285133 every 1.846 834 ± 0.000 002 d. Our high-precision radial velocity measurements present a variation with amplitude characteristic of a planetary-mass companion and in phase with the light curve. Adaptive optics imaging shows no evidence for nearby stellar companions, and line-bisector analysis excludes faint, unresolved binarity and stellar activity as the cause of the radial velocity variations. We make a preliminary spectroscopic analysis of the host star and find it to have T eff = 6400 ± 100 K and log g = 4.25 ± 0.05 which suggests it is most likely an unevolved main-sequence star of spectral type F7-8V. Our simultaneous modelling of the transit photometry and reflex motion of the host leads us to derive a mass of 1.76 +0.08 −0.14 MJ and radius 1.31 +0.07 −0.14 RJ for WASP-3b. The proximity and relative temperature of the host star suggests that WASP-3b is one of the hottest exoplanets known, and thus has the potential to place stringent constraints on exoplanet atmospheric models.

The Survey of Low-Mass X-Ray Binaries with the Einstein Observatory Solid-State Spectrometer and Monitor Proportional Counter

We report on the discovery of WASP-12b, a new transiting extrasolar planet with R pl = 1.79+0.09 –0.09 RJ and M pl = 1.41+0.10 –0.10 M J. The planet and host star properties were derived from a Monte Carlo Markov Chain analysis of the transit photometry and radial velocity data. Furthermore, by comparing the stellar spectrum with theoretical spectra and stellar evolution models, we determined that the host star is a supersolar metallicity ([M/H] = 0.3+0.05 –0.15), late-F (T eff = 6300+200 –100 K) star which is evolving off the zero-age main sequence. The planet has an equilibrium temperature of T eq = 2516 K caused by its very short period orbit (P = 1.09 days) around the hot, twelfth magnitude host star. WASP-12b has the largest radius of any transiting planet yet detected. It is also the most heavily irradiated and the shortest period planet in the literature.

New periodic variable stars coincident with ROSAT sources discovered using SuperWASP

We present a fast and efficient hybrid algorithm for selecting exoplanetary candidates from wide-field transit surveys. Our method is based on the widely used SysRem and Box Least-Squares (BLS) algorithms. Patterns of systematic error that are common to all stars on the frame are mapped and eliminated using the SysRem algorithm. The remaining systematic errors caused by spatially localized flat-fielding and other errors are quantified using a boxcar-smoothing method. We show that the dimensions of the search-parameter space can be reduced greatly by carrying out an initial BLS search on a coarse grid of reduced dimensions, followed by Newton-Raphson refinement of the transit parameters in the vicinity of the most significant solutions. We illustrate the methods operation by applying it to data from one field of the SuperWASP survey, comprising 2300 observations of 7840 stars brighter than V = 13.0. We identify 11 likely transit candidates. We reject stars that exhibit significant ellipsoidal variations caused indicative of a stellar-mass companion. We use colours and proper motions from the Two Micron All Sky Survey and USNO-B1.0 surveys to estimate the stellar parameters and the companion radius. We find that two stars showing unambiguous transit signals pass all these tests, and so qualify for detailed high-resolution spectroscopic follow-up.

The main-sequence rotation-colour relation in the Coma Berenices open cluster

The HEAO 2 or Einstein solid-state spectrometer (SSS; 0.5-4.5 keV) and monitor proportional counter (MPC; 1.2-20.0 keV) carried out an extensive survey of 49 low-mass X-ray binaries (LMXBs). Simultaneous SSS plus MPC spectra, selected on the basis of their intensity, were fitted with a set of simple and complex spectral models. For all the sources, including Eddington-limited bulge sources, bursters, dippers, the soft spectrum black hole candidates, and a few transients in decline, the spectra could be fitted acceptably with combinations of thermal bremsstrahlung and blackbody models or a Comptonized spectrum and a blackbody. The results rule out optically thick disk models for the bright (Z) sources and power-law models for the bursters. The SSS can confirm only the strongest of previously reported low-energy emission lines due to O VIII or Fe L transitions. Uncertainties in column densities are modest, and together with consideration of a disk distribution of gas and dust in the galaxy, the column densities provide distance estimates. These are the only measures yet available for eight sources. Several physical interpretations in terms of an optically thick component located on or very near the neutron star, an optically thin region farther in radius from the neutron star, and contribution of the accretion disk are possible. Assumptions required of the pulsar in a cocoon model are problematical. Correlations of spectral parameters with intensity observed in color-color diagrams are more complex than previously reported, although relating luminosity changes to the mass accretion rate is still tenable.