2012/10/31 by Neale P. Gibson, N. P. Gibson, S. Aigrain +5
Chemistry · Physics and Astronomy · #Artificial intelligence #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Computer science #Exoplanet #Light curve #Optics #Physics #Spectral line #Spectrograph #Spectroscopy and Laser Applications #Stars #Stellar, planetary, and galactic studies #Wavelength #Wavelet #astro-ph.EP
paper · pdf · doi:10.1093/mnras/sts307
15 pages, 9 figures, 3 tables. Published in MNRAS. Figure 2 corrected in version 2
openalex publication_date 2012/11/29 · arxiv created 2013/04/24 · arxiv updated 2015/06/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We report Gemini-South Gemini Multi-Object Spectrograph observations of the exoplanet system WASP-29 during primary transit as a test case for differential spectrophotometry. We use the multi-object spectrograph to observe the target star and a comparison star simultaneously to produce multiple light curves at varying wavelengths. The ‘white’ light curve and 15 ‘spectral’ light curves are analysed to refine the system parameters and produce a transmission spectrum from ∼515 to 720 nm. All light curves exhibit time-correlated noise, which we model using a variety of techniques. These include a simple noise rescaling, a Gaussian process model and a wavelet-based method. These methods all produce consistent results, although with different uncertainties. The precision of the transmission spectrum is improved by subtracting a common signal from all the spectral light curves, reaching a typical precision of ∼1 × 10−4 in transit depth. The transmission spectrum is free of spectral features, and given the non-detection of a pressure broadened Na feature, we can rule out the presence of a Na-rich atmosphere free of clouds or hazes, although we cannot rule out a narrow Na core. This indicates that Na is not present in the atmosphere, and/or that clouds/hazes play a significant role in the atmosphere and mask the broad wings of the Na feature, although the former is a more likely explanation given WASP-29b’s equilibrium temperature of ∼970 K, at which Na can form various compounds. We also briefly discuss the use of Gaussian process and wavelet methods to account for time-correlated noise in transit light curves.