The WASP (Wide Angle Search for Planets) project is an ultra-wide angle automated photometric survey, with the primary science goal of discovering transits of 'hot Jupiters'. SuperWASP-I, based on La Palma, Canary Islands, will begin fully robotic operations in 2005 with 8 cameras on a single fork mount, after running throughout April-November 2004 with 5 cameras. Construction of SuperWASP-II will begin at its South African site in mid-2005. The expected planet yield is of the order of a few tens per year, from a data flow of ~10-20 Tb of data per year. To deal with this vast amount of data, we have developed a custom-built data reduction pipeline and archive facility. Good transit candidates are expected from mid-2005.

1. Abstract

Precise transit photometry can reveal the signature of planets moving across the disk of their star (as illustrated, right). WASP follows the broad-shallow strategy in which thousands of bright stars are observed for the ~1% transits which announce Jupiter-radius companions. This ensures that candidate transiting objects will be well-suited for spectroscopic follow-up to eliminate the false-positives.

Transiting exoplanets are revolutionising our understanding of exoplanet physics, as currently they offer the only method of probing the inner structure, by providing a density from a true mass determination and planetary radius constraints (e.g. Sozzetti et al 2004). SuperWASP-I is by far the widest-field photometric survey currently in operation that is capable of better than 1% precision required for Hot-Jupiter transits, with a total field of view over the eight cameras nearly 500 square degrees.

2. Transit Photometrystar

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3. SuperWASP Specifications and Potential Yield

Each of SuperWASP's-I 11cm aperture cameras has a 7.8°x7.8° field of view, to observe thousands of stars at magnitudes 7<V<15, with better than 1% photometric precision for magnitudes up to ~12.

Each monitored field contains ~10,000 stars with V<12. Of these, around 14-19% are late-type F-M stars of which ~2% are expected to harbour giant planets, based on results from a decade of radial velocity surveys. Of those with planets, around 5% should present a transiting orientation. This results in ~1.5 real transits per field, being monitored for around 40 days. The plot to the right gives rms versus flux, showing the achieved photometric precision for a range of magnitudes.

Current Status of the WASP ProjectB. Enoch1, W.I. Clarkson1, D.J. Christian2, A. Collier Cameron3, A. Evans4, A.Fitzsimmons2,

C.A. Haswell1, C. Hellier4, S.T. Hodgkin5, K. Horne3, J. Irwin5, S.R. Kane3, F.P. Keenan2, T.A. Lister3, A.J. Norton1, J.Osborne6, D.L. Pollaco2, R. Ryans2, I. Skillen7, R.A. Street2, R.G. West6, P.J. Wheatley6

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4. Data reduction pipeline ●Pre-existing photometry software is inadequate for the wide FOV of the WASP cameras. A custom-built data pipeline has been developed:●Statistical frame-classification using minimal input assumptions●Optimal combination of master calibration frames from several nights, weighted by time interval and by quality●Calibration using flat, dark and bias frames, and correction for shutter travel time●Full astrometric solution of FOV using Tycho2 catalogue (<15 mag)●Object identification using USNO-B1 catalogue. Photometry performed for 3 separate apertures allowing a measure of object blending●Non-matched objects may be transient outbursts, gamma-ray bursts or asteroids; flagged as orphans for later re-examination

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●Post-photometry calibration; convert SW-I count rates to visual magnitudes from iterative fit to 9-term photometric model

●End-product can be queried flexibly from WASP archive based at Leicester University, which forms the primary interface to all post-processed science data. Time-evolution of object properties stored by keyword, (e.g. flux, CCD position vs time). Further keywords can be added as desired. Archive-query tools developed using custom-written WASP query language.

5. Preliminary ResultsThese figures show example lightcurves from the 2004 SW-I dataset, revealing large-amplitude (left) and low-amplitude (at the 1% level, right) variability of a selection of sources of interest. This demonstrates that SW-I has achieved the necessary <1% accuracy that will be needed to detect transiting exoplanets. A rich, comprehensive database of bright stellar variability is a natural by-product of the WASP datasets.

●Fully robotic, unattended operation of SW-I will begin with 8 cameras in 2005. ●Further refinement and optimisation of the pipeline

throughout early 2005.●Construction of the clone facility SW-II at the South African Astronomical Observatory, mid-2005.

Christian D.J. et al., 2004 astro-ph/0411019Kane S.R. et al., 2004 MNRAS 353,689Sozzetti A. et al, 2004 ApJ Lett 616, 167www.superwasp.org

6. The Future

7. References & Further Information

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Left: Schematic of exoplanet transit (top), and a real transit-lightcurve of HD209458B, taken with the WASP0 demonstration prototype (Kane et al 2004)

Above: Planetary mass-radius trend for transiting exoplanets. From Sozzetti et al (2004).

Views of the SW-I Facility.

Flow-diagram of the reduction pipeline stages.

Example frames from the automated pre-processing.

Flux-RMS diagram of all lightcurves from a single field of view for a single camera, from a sample of the 2004 SW-I dataset.

Sample variable-star lightcurves from the 2004 SW-I dataset. Stellar lightcurves from the 2004 SW-I dataset

showing 1%-level variations.

Pre-processed imageRaw image