ASTEP South: an Antarctic Search for Transiting ExoPlanets around the celestial south pole

Abstract

Context. The Concordia base in Dome C, Antarctica, is an extremely promising site for photometric astronomy due to the 3-month long night during the Antarctic winter, favorable weather conditions, and low scintillation. Aims. The ASTEP project (Antarctic Search for Transiting ExoPlanets) is a pilot project to discover transiting planets and understand the limits of visible photometry from the Concordia site. Methods. ASTEP South is the first phase of the ASTEP project. The instrument is a fixed 10 cm refractor with a 4k × 4k CCD camera in a thermalized box, pointing continuously a 3.88 × 3.88•2 field of view centered on the celestial south pole. We describe the project and report results of a preliminary data analysis. Results. ASTEP South became fully functional in June 2008 and obtained 1592 hours of data during the 2008 Antarctic winter. The data are of good quality but the analysis has to account for changes in the PSF (point spread function) due to rapid ground seeing variations and instrumental effects. The pointing direction is stable within 10 arcsec on a daily timescale and drifts by only 34 arcsec in 50 days. A truly continuous photometry of bright stars is possible in June (the noon sky background peaks at a magnitude R ≈ 15 arcsec −2 on June 22), but becomes challenging in July (the noon sky background magnitude is R ≈ 12.5 arcsec −2 on July 20). The weather conditions are estimated from the number of stars detected in the field. For the 2008 winter, the statistics are between 56.3% and 68.4% of excellent weather, 17.9% to 30% of veiled weather (when the probable presence of thin clouds implies a lower number of detected stars) and 13.7% of bad weather. Using these results in a probabilistic analysis of transit detection, we show that the detection efficiency of transiting exoplanets in one given field is improved at Dome C compared to a temperate site such as La Silla. For example we estimate that a year-long campaign of 10 cm refractor could reach an efficiency of 69% at Dome C versus 45% at La Silla for detecting 2-day period giant planets around target stars from magnitude 10 to 15. The detection efficiency decreases for planets with longer orbital periods, but in relative sense it is even more favorable to Dome C. Conclusions. This shows the high potential of Dome C for photometry and future planet discoveries.

The EBLM Project

“…Another important goal is to warn fellow planet hunters operating within the celestial Southern Hemisphere HATSouth (Bakos et al 2013), KELT (Pepper et al 2012), ASTEP (Crouzet et al 2010), NGTS (Wheatley et al 2013), K2 (Howell et al 2014), TESS (Ricker et al 2014) where are located many systems most likely to masquerade as hot Jupiters.…”

Variable Stars Observed in the Galactic Disk by AST3-1 from Dome A, Antarctica

“…There is thus considerable interest in overcoming the technical challenges of operating in Antarctica, so that the advantages for astronomy can be realized (Tothill et al 2008;Kulesa et al 2008;Crouzet et al 2010;Chapellier et al 2016;Mékarnia et al 2016). Dome A (latitude 80…”

The secondary eclipses of WASP-19b as seen by the ASTEP 400 telescope from Antarctica

“…As described by Crouzet et al (2010), the Dome C has excellent meteorological conditions and near-continuous observations are possible for approximately three months centered on the Southern winter solstice (June 21st). This makes it an ideal site for long-duration observations such as those required to characterize the phase curves of exoplanets.…”