A sensitivity analysis of the WFCAM Transit Survey for short-period giant planets around M dwarfs

The WFCAM Transit Survey (WTS) is a near-infrared transit survey running on the United Kingdom Infrared Telescope (UKIRT), designed to discover planets around M dwarfs. The WTS acts as a poor-seeing backup programme for the telescope, and represents the first dedicated wide-field near-infrared transit survey. In this paper we describe the observing strategy of the WTS and the processing of the data to generate lightcurves. We describe the basic properties of our photometric data, and measure our sensitivity based on 950 observations. We show that the photometry reaches a precision of ~4mmag for the brightest unsaturated stars in lightcurves spanning almost 3 years. Optical (SDSS griz) and near-infrared (UKIRT ZYJHK) photometry is used to classify the target sample of 4600 M dwarfs with J magnitudes in the range 11-17. Most have spectral-types in the range M0-M2. We conduct Monte Carlo transit injection and detection simulations for short period (<10 day) Jupiter- and Neptune-sized planets to characterize the sensitivity of the survey. We investigate the recovery rate as a function of period and magnitude for 4 hypothetical star-planet cases: M0-2+Jupiter, M2-4+Jupiter, M0-2+Neptune, M2-4+Neptune. We find that the WTS lightcurves are very sensitive to the presence of Jupiter-sized short-period transiting planets around M dwarfs. Hot Neptunes produce a much weaker signal and suffer a correspondingly smaller recovery fraction. Neptunes can only be reliably recovered with the correct period around the rather small sample (~100) of the latest M dwarfs (M4-M9) in the WTS. The non-detection of a hot-Jupiter around an M dwarf by the WFCAM Transit Survey allows us to place an upper limit of 1.7-2.0 per cent (at 95 per cent confidence) on the planet occurrence rate.

[1]  A. Pál.  Properties of analytic transit light-curve models , 2008 .

[2]  James P. Emerson,et al.  VISTA data flow system: pipeline processing for WFCAM and VISTA , 2004, SPIE Astronomical Telescopes + Instrumentation.

[3]  R. Drimmel,et al.  A three-dimensional Galactic extinction model , 2003, astro-ph/0307273.

[4]  Timothy M. Brown,et al.  KEPLER INPUT CATALOG: PHOTOMETRIC CALIBRATION AND STELLAR CLASSIFICATION , 2011, 1102.0342.

[5]  M. R. Haas,et al.  PLANET OCCURRENCE WITHIN 0.25 AU OF SOLAR-TYPE STARS FROM KEPLER , 2011, 1103.2541.

[6]  M. Irwin,et al.  Automatic Analysis of Crowded Fields , 1985 .

[7]  E. Greisen,et al.  Representations of celestial coordinates in FITS , 2002, astro-ph/0207413.

[8]  Stephen R. Kane,et al.  CHARACTERIZING THE VARIABILITY OF STARS WITH EARLY-RELEASE KEPLER DATA , 2010, 1009.1840.

[9]  S. Leggett.  Infrared Colors of Low-Mass Stars , 1992 .

[10]  Peter Plavchan,et al.  Near-Infrared Variability in the 2MASS Calibration Fields: A Search for Planetary Transit Candidates , 2007, 0709.1182.

[11]  Adam A. Miller,et al.  The Monitor project : the search for transits in the open cluster NGC 2362 , 2008, 0803.4004.

[12]  CHARACTERIZING THE COOL KOIs. II. THE M DWARF KOI-254 AND ITS HOT JUPITER* , 2011, 1112.0017.

[13]  David Charbonneau,et al.  TRANSIT DETECTION IN THE MEarth SURVEY OF NEARBY M DWARFS: BRIDGING THE CLEAN-FIRST, SEARCH-LATER DIVIDE , 2012, 1206.4715.

[14]  S. Aigrain,et al.  Practical planet prospecting , 2004 .

[15]  M. C. Gálvez-Ortiz,et al.  J‐band variability of M dwarfs in the WFCAM Transit Survey , 2012, 1211.5288.

[16]  Suzanne Aigrain,et al.  The Monitor project: data processing and light curve production , 2006 .

[17]  K. Abazajian,et al.  THE SEVENTH DATA RELEASE OF THE SLOAN DIGITAL SKY SURVEY , 2008, 0812.0649.

[18]  R. Paul Butler,et al.  A New Planet around an M Dwarf: Revealing a Correlation between Exoplanets and Stellar Mass , 2007, 0707.2409.

[19]  Xavier Bonfils,et al.  A super-Earth transiting a nearby low-mass star , 2009, Nature.

[20]  B. Scott Gaudi,et al.  Fraction of Stars With Planets in the Open Cluster NGC 1245 , 2004 .

[21]  D. Queloz,et al.  Detection of transits of the nearby hot Neptune GJ 436 b , 2007, Astronomy &amp; Astrophysics.

[22]  Scott J. Kenyon,et al.  Planet Formation around Stars of Various Masses: The Snow Line and the Frequency of Giant Planets , 2007, 0710.1065.

[23]  Gilles Chabrier,et al.  Evolution of low-mass star and brown dwarf eclipsing binaries , 2007, 0707.1792.

[24]  M. Irwin,et al.  INT WFS pipeline processing , 2001 .

[25]  Andrew A. West,et al.  Stellar SEDs from 0.3 to 2.5 μm: Tracing the Stellar Locus and Searching for Color Outliers in the SDSS and 2MASS , 2007, 0707.4473.

[26]  S. T. Hodgkin,et al.  The UKIRT wide field camera ZYJHK photometric system: calibration from 2MASS , 2008, 0812.3081.

[27]  Philipp Eigmüller,et al.  NGTS: a robotic transit survey to detect Neptune and super-Earth mass planets , 2012, Other Conferences.

[28]  J. E. O'Donnell.  R(sub nu)-dependent optical and near-ultraviolet extinction , 1994 .

[29]  M. Osorio,et al.  Search for radial velocity variations in eight M-dwarfs with NIRSPEC/Keck II , 2011, 1112.1382.

[30]  M. Skrutskie,et al.  The Two Micron All Sky Survey (2MASS) , 2006 .

[31]  G. Chabrier.  Galactic Stellar and Substellar Initial Mass Function , 2003, astro-ph/0304382.

[32]  Frederic Pont,et al.  The effect of red noise on planetary transit detection , 2006, astro-ph/0608597.

[33]  B. Sipocz,et al.  The first planet detected in the WTS: an inflated hot Jupiter in a 3.35 d orbit around a late F star , 2012, 1210.1217.

[34]  E. Gaidos,et al.  THEY MIGHT BE GIANTS: LUMINOSITY CLASS, PLANET OCCURRENCE, AND PLANET–METALLICITY RELATION OF THE COOLEST KEPLER TARGET STARS , 2012, 1202.5394.

[35]  G. Kov'acs,et al.  A box-fitting algorithm in the search for periodic transits , 2002, astro-ph/0206099.

[36]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .

[37]  F. Fressin,et al.  CHARACTERISTICS OF PLANETARY CANDIDATES OBSERVED BY KEPLER. II. ANALYSIS OF THE FIRST FOUR MONTHS OF DATA , 2011, 1102.0541.

[38]  Andrew Cumming,et al.  The Keck Planet Search: Detectability and the Minimum Mass and Orbital Period Distribution of Extrasolar Planets , 2008, 0803.3357.

[39]  R. A. Street,et al.  FREQUENCY OF SOLAR-LIKE SYSTEMS AND OF ICE AND GAS GIANTS BEYOND THE SNOW LINE FROM HIGH-MAGNIFICATION MICROLENSING EVENTS IN 2005–2008 , 2010, 1001.0572.

[40]  Adam L. Kraus,et al.  THE MASS–RADIUS(–ROTATION?) RELATION FOR LOW-MASS STARS , 2010, 1011.2757.

[41]  J. Mathis,et al.  The relationship between infrared, optical, and ultraviolet extinction , 1989 .

[42]  B. Monard,et al.  MOA-2009-BLG-387Lb: a massive planet orbiting an M dwarf , 2011, 1102.0558.

[43]  Shay Zucker,et al.  Directed follow-up strategy of low-cadence photometric surveys in search of transiting exoplanets - I. Bayesian approach for adaptive scheduling , 2011, 1105.5393.

[44]  G. Fasano,et al.  A multidimensional version of the Kolmogorov–Smirnov test , 1987 .

[45]  Frequency of Hot Jupiters and Very Hot Jupiters from the OGLE-III Transit Surveys Toward the Galactic Bulge and Carina , 2006, astro-ph/0601001.

[46]  Saurav Dhital,et al.  THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 7 SPECTROSCOPIC M DWARF CATALOG. I. DATA , 2011, 1101.1082.

[47]  Gregory Laughlin,et al.  The Core Accretion Model Predicts Few Jovian-Mass Planets Orbiting Red Dwarfs , 2004, astro-ph/0407309.

[48]  Cambridge,et al.  The UKIRT Infrared Deep Sky Survey ZY JHK photometric system: passbands and synthetic colours , 2006, astro-ph/0601592.

[49]  John Asher Johnson,et al.  Giant Planet Occurrence in the Stellar Mass-Metallicity Plane , 2010, 1005.3084.

[50]  Douglas N. C. Lin,et al.  Toward a Deterministic Model of Planetary Formation. V. Accumulation Near the Ice Line and Super-Earths , 2008 .

[51]  John Asher Johnson,et al.  THE FREQUENCY OF HOT JUPITERS ORBITING NEARBY SOLAR-TYPE STARS , 2012, 1205.2273.

[52]  F. Rasio,et al.  Gas Disks to Gas Giants: Simulating the Birth of Planetary Systems , 2008, Science.

[53]  Adam L. Kraus,et al.  THREE NEW ECLIPSING WHITE-DWARF–M-DWARF BINARIES DISCOVERED IN A SEARCH FOR TRANSITING PLANETS AROUND M-DWARFS , 2011, The Astrophysical Journal.

[54]  D. Schlegel,et al.  Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds , 1997, astro-ph/9710327.

[55]  M. Irwin,et al.  The UKIRT Infrared Deep Sky Survey (UKIDSS) , 2006, astro-ph/0604426.

[56]  Gilles Chabrier,et al.  Mass-Spectral Class Relationship for M Dwarfs , 1996 .

[57]  E. Agol,et al.  Analytic Light Curves for Planetary Transit Searches , 2002, astro-ph/0210099.

[58]  C. G. Tinney,et al.  Observed Properties of Exoplanets : Masses, Orbits, and Metallicities(Origins : From Early Universe to Extrasolar Planets) , 2005 .

[59]  D. Soderblom.  Planets Beyond the Solar System and the Next Generation of Space Missions , 1997 .

[60]  S Ida,et al.  Toward a Deterministic Model of Planetary Formation. III. Mass Distribution of Short-Period Planets around Stars of Various Masses , 2005 .

[61]  Investigating the potential of the Pan-Planets project using Monte Carlo simulations , 2008, 0812.1559.

[62]  Mark R. Calabretta,et al.  Representations of world coordinates in FITS , 2002, astro-ph/0207407.

[63]  M. Pinsonneault,et al.  DEEP MMT TRANSIT SURVEY OF THE OPEN CLUSTER M37 IV: LIMIT ON THE FRACTION OF STARS WITH PLANETS AS SMALL AS 0.3RJ , 2008, 0809.3807.

[64]  Rapid Formation of Gas Giant Planets around M Dwarf Stars , 2006, astro-ph/0601486.

[65]  Darko Jevremovic,et al.  The Dartmouth Stellar Evolution Database , 2008, 0804.4473.