WASP-10b: a 3MJ, gas-giant planet transiting a late-type K star

We report the discovery of WASP-10b, a new transiting extrasolar planet (ESP) discovered by the Wide Angle Search for Planets (WASP) Consortium and confirmed using Nordic Optical Telescope FIbre-fed Echelle Spectrograph and SOPHIE radial velocity data. A 3.09-d period, 29 mmag transit depth and 2.36 h duration are derived for WASP-10b using WASP and high-precision photometric observations. Simultaneous fitting to the photometric and radial velocity data using a Markov Chain Monte Carlo procedure leads to a planet radius of  1.28 R _J   , a mass of  2.96 M _J   and eccentricity of ≈0.06. WASP-10b is one of the more massive transiting ESPs, and we compare its characteristics to the current sample of transiting ESP, where there is currently little information for masses greater than ≈  2 M _J   and non-zero eccentricities. WASP-10's host star, GSC 2752−00114 (USNO-B1.0 1214−0586164) is among the fainter stars in the WASP sample, with   V = 12.7  and a spectral type of K5. This result shows promise for future late-type dwarf star surveys.     

A trend filtering algorithm for wide-field variability surveys

We show that various systematics related to certain instrumental effects and data reduction anomalies in wide-field variability surveys can be efficiently corrected by a trend filtering algorithm (TFA) applied to the photometric time-series produced by standard data pipelines. Statistical tests, performed on the data base of the HAT Network project, show that by the application of this filtering method the cumulative detection probability of periodic transits increases by up to 0.4 for variables brighter than 11 mag, with a trend of increasing efficiency toward brighter magnitudes. We also show that the TFA can be used for the reconstruction of periodic signals by iteratively filtering out systematic distortions.     

Planetary transit observations at the University Observatory Jena: TrES‐2

We report on observations of several transit events of the transiting planet TrES‐2 obtained with the Cassegrain‐Teleskop‐Kamera at the University Observatory Jena. Between March 2007 and November 2008 ten different transits and almost a complete orbital period were observed. Overall, in 40 nights of observation 4291 exposures (in total 71.52 h of observation) of the TrES‐2 parent star were taken. With the transit timings for TrES‐2 from the 34 events published by the TrES‐network, the Transit Light Curve project and the Exoplanet Transit Database plus our own ten transits, we find that the orbital period is P = (2.470614 ± 0.000001) d, a slight change by ∼0.6 s compared to the previously published period. We present new ephemeris for this transiting planet. Furthermore, we found a second dip after the transit which could either be due to a blended variable star or occultation of a second star or even an additional object in the system. Our observations will be useful for future investigations of timing variations caused by additional perturbing planets and/or stellar spots and/or moons (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

K-band transit and secondary eclipse photometry of exoplanet OGLE-TR-113b

We present high-precision K -band photometry of the transit and secondary eclipse of extrasolar planet OGLE-TR-113, using the SOFI near-infrared instrument on European Southern Observatory's New Technology Telescope. Data were taken in 5-s exposures over two periods of 3–4 h, using random jitter position offsets. In this way, a relative photometric precision of ∼1 per cent per frame was achieved, avoiding systematic effects that seem to become dominant at precisions exceeding this level, and resulting in an overall accuracy of 0.1 per cent per ∼10 min. The observations of the transit show a flat-bottomed light-curve indicative of a significantly lower stellar limb darkening at near-infrared than at optical wavelengths. The observations of the secondary eclipse result in a 3σ detection of emission from the exoplanet at 0.17 ± 0.05 per cent. However, residual systematic errors make this detection rather tentative.     

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

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 radial-velocity 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 R _Jup, whereas WASP-2b has a radius in the range 0.65–1.26 R _Jup.     

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

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 M _J  and radius  1.31^+0.07_−0.14 R _J  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.     

A SuperWASP search for additional transiting planets in 24 known systems

We present results from a search for additional transiting planets in 24 systems already known to contain a transiting planet. We model the transits due to the known planet in each system and subtract these models from light curves obtained with the SuperWASP (Wide Angle Search for Planets) survey instruments. These residual light curves are then searched for evidence of additional periodic transit events. Although we do not find any evidence for additional planets in any of the planetary systems studied, we are able to characterize our ability to find such planets by means of Monte Carlo simulations. Artificially generated transit signals corresponding to planets with a range of sizes and orbital periods were injected into the SuperWASP photometry and the resulting light curves searched for planets. As a result, the detection efficiency as a function of both the radius and orbital period of any second planet is calculated. We determine that there is a good (>50 per cent) chance of detecting additional, Saturn-sized planets in   P ∼  10 d orbits around planet-hosting stars that have several seasons of SuperWASP photometry. Additionally, we confirm previous evidence of the rotational stellar variability of WASP-10, and refine the period of rotation. We find that the period of the rotation is  11.91 ± 0.05  d, and the false alarm probability for this period is extremely low  (∼10⁻¹³)  .     

An optimal extraction algorithm for imaging photometry

This paper is primarily an investigation of whether the 'optimal extraction' techniques used in CCD spectroscopy can be applied to imaging photometry. It is found that using such techniques provides a gain of around 10 per cent in signal-to-noise ratio over normal aperture photometry. Formally, it is shown to be equivalent to profile fitting, but offers advantages of robust error estimation, freedom from bias introduced by mis-estimating the point spread function, and convenience. In addition some other techniques are presented, which can be applied to profile fitting, aperture photometry and the 'optimal' photometry. Code implementing these algorithms is available at http://www.astro.keele.ac.uk/~timn/.     

L' and M' standard stars for the Mauna Kea Observatories Near-Infrared system

We present L ' and M ' photometry, obtained at the United Kingdom Infrared Telescope (UKIRT) using the Mauna Kea Observatories Near-Infrared (MKO-NIR) filter set, for 46 and 31 standard stars, respectively. The L ' standards include 25 from the in-house 'UKIRT Bright Standards' with magnitudes deriving from Elias et al. and observations at the Infrared Telescope Facility in the early 1980s, and 21 fainter stars. The M ' magnitudes derive from the results of Sinton and Tittemore. We estimate the average external error to be 0.015 mag for the bright L ' standards and 0.025 mag for the fainter L ' standards, and 0.026 mag for the M ' standards. The new results provide a network of homogeneously observed standards, and establish reference stars for the MKO system, in these bands. They also extend the available standards to magnitudes which should be faint enough to be accessible for observations with modern detectors on large and very large telescopes.     

Prospects for spectroscopic reflected-light planet searches

High-resolution spectroscopic searches for the starlight reflected from close-in extrasolar giant planets have the capability of determining the optical albedo spectra and scattering properties of these objects. When combined with radial velocity measurements they also yield the true mass of the planet. To date, only two such planets have been targeted for reflected-light signals, yielding upper limits on the optical albedos of the planets. Here we examine the prospects for future searches of this kind. We present Monte Carlo estimates of prior probability distributions for the orbital velocity amplitudes and planet/star flux ratios of six bright stars known to harbour giant planets in orbits with periods of less than 5 d. Using these estimates, we assess the viability of these targets for future reflected-light searches using 4- and 8-m class telescopes.     

Detectability of exoplanetary transits from radial velocity surveys

Of the known transiting extrasolar planets, a few have been detected through photometric follow-up observations of radial velocity planets. Perhaps the best known of these is the transiting exoplanet HD 209458b. For hot Jupiters (periods less than ∼5 d), the a priori information that 10 per cent of these planets will transit their parent star due to the geometric transit probability leads to an estimate of the expected transit yields from radial velocity surveys. The radial velocity information can be used to construct an effective photometric follow-up strategy which will provide optimal detection of possible transits. Since the planet-harbouring stars are already known in this case, one is only limited by the photometric precision achievable by the chosen telescope/instrument. The radial velocity modelling code presented here automatically produces a transit ephemeris for each planet data set fitted by the program. Since the transit duration is brief compared with the fitted period, we calculate the maximum window for obtaining photometric transit observations after the radial velocity data have been obtained, generalizing for eccentric orbits. We discuss a typically employed survey strategy which may contribute to a possible radial velocity bias against detection of the very hot Jupiters which have dominated the transit discoveries. Finally, we describe how these methods can be applied to current and future radial velocity surveys.