5 research outputs found
- A tool for multiband light curve modeling of planetary transits and stellar spots
Several studies have shown that stellar activity features, such as occulted
and non-occulted starspots, can affect the measurement of transit parameters
biasing studies of transit timing variations and transmission spectra. We
present , which we designed to model multiband transit
light curves showing starspot anomalies, inferring both transit and spot
parameters. The code follows a pixellation approach to model the star with its
corresponding limb darkening, spots, and transiting planet on a two dimensional
Cartesian coordinate grid. We combine with an MCMC
framework to study and derive exoplanet transmission spectra, which provides
statistically robust values for the physical properties and uncertainties of a
transiting star-planet system. We validate 's performance
by analyzing eleven synthetic light curves of four different star-planet
systems and 20 transit light curves of the well-studied WASP-41b system. We
also investigate the impact of starspots on transit parameters and derive
wavelength dependent transit depth values for WASP-41b covering a range of
6200-9200 , indicating a flat transmission spectrum.Comment: 17 pages, 22 figures; accepted for publication in Astronomy &
Astrophysic
High precision ground-based CCD photometry from the Next Generation Transit Survey
The Next Generation Transit Survey (NGTS) has now been operating for six years, discovering and characterizing transiting exoplanets around bright stars. We outline the NGTS project, including the Andor CCD cameras used to perform high-precision time-series photometry. We quantify the photometric precision for a sample of over 20,000 bright star observations. We find for single NGTS telescope observations we achieve a 30-minute photometric precision of 400 ppm at low airmass. This is in good agreement with the photometric noise predicted using a four-component noise model. We find that the photometric noise for bright stars (G < 12) is dominated by atmospheric scintillation. We also present details of the NGTS multi-telescope observing mode, whereby 12 telescopes can be used simultaneously on a single target star to achieve a 30-minute photometric precision of 100 ppm. Finally, we describe a new generation scientific CMOS camera that we will be testing on-sky at the NGTS facility to determine if it can compete with state-of-the-art CCD cameras used for high precision bright star photometry