Observations of the WASP-2 System by the APOSTLE Program

Abstract

We present transit observations of the WASP-2 exoplanet system by the Apache Point Survey of Transit Lightcurves of Exoplanets (APOSTLE) program. Model fitting to these data allows us to improve measurements of the hot-Jupiter exoplanet WASP-2b and its orbital parameters by a factor of ~2 over prior studies; we do not find evidence for transit depth variations. We do find reduced chi^2 values greater than 1.0 in the observed minus computed transit times. A sinusoidal fit to the residuals yields a timing semi-amplitude of 32 seconds and a period of 389 days. However, random rearrangements of the data provide similar quality fits, and we cannot with certainty ascribe the timing variations to mutual exoplanet interactions. This inconclusive result is consistent with the lack of incontrovertible transit timing variations (TTVs) observed in other hot-Jupiter systems. This outcome emphasizes that unique recognition of TTVs requires dense sampling of the libration cycle (e.g. continuous observations from space-based platforms). However, even in systems observed with the Kepler spacecraft, there is a noted lack of transiting companions and TTVs in hot-Jupiter systems. This result is more meaningful, and indicates that hot-Jupiter systems, while they are easily observable from the ground, do not appear to be currently configured in a manner favorable to the detection of TTVs. The future of ground-based TTV studies may reside in resolving secular trends, and/or implementation at extreme quality observing sites to minimize atmospheric red noise.

ApJ Letters, accepted

References in corpus (20)

• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates
• DHP Framework: Digital Health Passports Using Blockchain -- Use case on international tourism during the COVID-19 pandemic
• Empirical Color Transformations Between SDSS Photometry and Other Photometric Systems
• SDSS Standard Star Catalog for Stripe 82: the Dawn of Industrial 1% Optical Photometry
• WASP-1b and WASP-2b: Two new transiting exoplanets detected with SuperWASP and SOPHIE
• Kepler constraints on planets near hot Jupiters
• Transit Timing Observations from Kepler: IV. Confirmation of 4 Multiple Planet Systems by Simple Physical Models
• The TRAPPIST survey of southern transiting planets. I. Thirty eclipses of the ultra-short period planet WASP-43 b
• Transit Timing Observations from Kepler: III. Confirmation of 4 Multiple Planet Systems by a Fourier-Domain Study of Anti-correlated Transit Timing Variations
• The effect of stellar limb darkening values on the accuracy of the planet radii derived from photometric transit observations
• Transit Timing Observations from Kepler: II. Confirmation of Two Multiplanet Systems via a Non-parametric Correlation Analysis
• Extrasolar Planet Transits Observed at Kitt Peak National Observatory
• The Transit Light Curve Project. XI. Submillimagnitude Photometry of Two Transits of the Bloated Planet WASP-4b
• Towards More Precise Survey Photometry for PanSTARRS and LSST: Measuring Directly the Optical Transmission Spectrum of the Atmosphere
• Transit Monitoring in the South (TraMoS) project: Discarding Transit Timing Variations in WASP-5b
• Degeneracy in the characterization of non-transiting planets from transit timing variations
• Improved $u^{\prime }{g}^{\prime }{r}^{\prime }{i}^{\prime }{z}^{\prime }$ to $UBV{R}_C{I}_C$ Transformation Equations for Main Sequence Stars
• APOSTLE: Eleven Transit Observations of TrES-3b
• Detection of transit timing variations in excess of one hour in the Kepler multi-planet candidate system KOI 806 with the GTC

Cited by in corpus (6)

• TESS Transit Timing of Hundreds of Hot Jupiters
• ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations
• ExoClock project II: A large-scale integrated study with 180 updated exoplanet ephemerides
• Investigating the physical properties of transiting hot Jupiters with the 1.5-m Kuiper Telescope
• Kepler Object of Interest Network I. First results combining ground and space-based observations of Kepler systems with transit timing variations
• APOSTLE: Longterm Transit Monitoring and Stability Analysis of XO-2b