NASA’s Transiting Exoplanet Survey Satellite (TESS) monitors more than 200,000 stars in the search for transiting exoplanets. One of the primary goals of the TESS mission is to identify 50 planets smaller than four Earth radii with measured masses . Because of the wide field of view and corresponding large pixel size of the TESS telescope, high precision ground-based observations are needed to confirm planetary transits and eliminate false positives . The TESS Follow-up Observing Program Sub Group 1 (TFOP SG1) was developed to coordinate ground-based photometric follow-up observations .
The Adams Observatory at Austin College provides ground-based photometric support for the TESS project through TFOP SG1. Located on the roof of the IDEA Center science building, this facility houses the largest research telescope in north Texas and offers outstanding opportunities for research, education, and public outreach. In addition to TFOP, the Adams Observatory contributed to exoplanet transit observations as a member of the KELT Follow-Up Network . The main telescope at the Adams Observatory is a 0.61-m f/8 DFM telescope of Ritchey-Chrétien design. When coupled with a Finger Lakes Instruments (FLI) Proline 16803 imager, this system produces a 26’ × 26’ field of view and a 0.38” pixel scale. Under optimal conditions, we can detect a minimum transit depth of ~3.0 ppt, which for an M-dwarf star would correspond to an exoplanet with radius ~3 Earth radii.
In summer 2020, we observed 11 stars identified by the TESS Science Team as potentially having exoplanets. Our high-precision follow-up observations offer three possible scenarios for these TESS targets: 1) a light curve from the target star indicating a possible transiting exoplanet, 2) a light curve from a nearby star indicating a nearby eclipsing binary (NEB) star system, and 3) flat light curves for both the target star and nearby stars. Of the 11 stars, four stars exhibit Case 1 behavior and have been verified as planetary candidates. An NEB has been detected near one target star (Case 2), and the star has been “retired” from TESS exoplanet studies. Six observations exhibit flat light curves (Case 3), which could indicate that either the planet is too small (and the corresponding dip in light too shallow) for detection at the Adams Observatory, or that the TESS observation is a false positive. These results may be useful for eliminating other possible causes of light curve variations in the search for small Earth-sized exoplanets.
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