Detection capability of ground-based meter-sized telescopes for shallow exoplanet transits

Abstract

Meter-sized ground-based telescopes are frequently used today for the follow-up of extrasolar planet candidates. While the transit signal of a Jupiter-sized object can typically be detected to a high level of confidence with small telescope apertures as well, the shallow transit dips of planets with the size of Neptune and smaller are more challenging to reveal. We employ new observational data to illustrate the photometric follow-up capabilities of meter-sized telescopes for shallow exoplanet transits. We describe in detail the capability of distinguishing the photometric signal of an exoplanet transit from an underlying trend in the light curve. The transit depths of the six targets we observed, Kepler-94b, Kepler-63b, K2-100b, K2-138b, K2-138c, and K2-138e, range from 3.9 ppt down to 0.3 ppt. For five targets of this sample, we provide the first ground-based photometric follow-up. We detect or rule out the transit features significantly in single observations for the targets that show transits of 1.3 ppt or deeper. The shallower transit depths of two targets of 0.6 and 0.8 ppt were detected tentatively in single light curves, and were detected significantly by repeated observations. Only for the target of the shallowest transit depth of 0.3 ppt were we unable to draw a significant conclusion despite combining five individual light curves. An injection-recovery test on our real data shows that we detect transits of 1.3 ppt depth significantly in single light curves if the transit is fully covered, including out-of-transit data toward both sides, in some cases down to 0.7 ppt depth. For Kepler-94b, Kepler-63b, and K2-100b, we were able to verify the ephemeris. In the case of K2-138c with a 0.6 ppt deep transit, we were able to refine it, and in the case of K2-138e, we ruled out the transit in the time interval of more than +-1.5 sigma of its current literature ephemeris.

accepted for publication in Astronomy & Astrophysics

References in corpus (18)

• The Transiting Exoplanet Survey Satellite
• The effect of red noise on planetary transit detection
• The TESS Objects of Interest Catalog from the TESS Prime Mission
• Homogeneous studies of transiting extrasolar planets. I. Light curve analyses
• The Transit Light Curve Project. IX. Evidence for a Smaller Radius of the Exoplanet XO-3b
• The Orbit of WASP-12b is Decaying
• Zodiacal Exoplanets in Time (ZEIT) IV: seven transiting planets in the Praesepe cluster
• The L 98-59 System: Three Transiting, Terrestrial-Sized Planets Orbiting a Nearby M-dwarf
• High accuracy transit photometry of the planet OGLE-TR-113b with a new deconvolution-based method
• The K2-138 System: A Near-Resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists
• A photometric study of the hot exoplanet WASP-19b
• Exoplanet characterisation in the longest known resonant chain: the K2-138 system seen by HARPS
• GJ 1252 b: A 1.2 $R_{\oplus }$ planet transiting an M3-dwarf at 20.4 pc
• TOI-216b and TOI-216c: Two warm, large exoplanets in or slightly wide of the 2:1 orbital resonance
• High-precision multi-wavelength eclipse photometry of the ultra-hot gas giant exoplanet WASP-103 b
• Broad-band spectrophotometry of HAT-P-32 b: Search for a scattering signature in the planetary spectrum
• Ground-based photometry of the 21-day Neptune HD106315c
• Transmission spectroscopy of the hot Jupiter TrES-3 b: Disproof of an overly large Rayleigh-like feature

Cited by in corpus (5)

• DREAM I. Orbital architecture orrery
• DREAM: III.A helium survey in exoplanets on the edge of the hot Neptune desert with GIANO-B@TNG
• ATREIDES I. Embarking on a trek across the exo-Neptunian landscape with the TOI-421 system
• On the parameter refinement of inflated exoplanets with large radius uncertainty based on TESS observations
• Discovery of a transiting hot water-world candidate orbiting Ross 176 with TESS and CARMENES