The Transiting Exoplanet Survey Satellite: Simulations of planet detections and astrophysical false positives (1506.03845v4)

Abstract: The Transiting Exoplanet Survey Satellite (TESS) is a NASA-sponsored Explorer mission that will perform a wide-field survey for planets that transit bright host stars. Here, we predict the properties of the transiting planets that TESS will detect along with the eclipsing binary stars that produce false-positive photometric signals. The predictions are based on Monte Carlo simulations of the nearby population of stars, occurrence rates of planets derived from Kepler, and models for the photometric performance and sky coverage of the TESS cameras. We expect that TESS will find approximately 1700 transiting planets from 200,000 pre-selected target stars. This includes 556 planets smaller than twice the size of Earth, of which 419 are hosted by M dwarf stars and 137 are hosted by FGK dwarfs. Approximately 130 of the $R < 2~R_\oplus$ planets will have host stars brighter than K = 9. Approximately 48 of the planets with $R < 2~R_\oplus$ lie within or near the habitable zone ($0.2 < S/S_\oplus < 2$), and between 2-7 such planets have host stars brighter than K = 9. We also expect approximately 1100 detections of planets with radii 2-4 R_Earth, and 67 planets larger than $4~R_\oplus$. Additional planets larger than $2~R_\oplus$ can be detected around stars that are not among the pre-selected target stars, because TESS will also deliver full-frame images at a 30-minute cadence. The planet detections are accompanied by over one thousand astrophysical false positives. We discuss how TESS data and ground-based observations can be used to distinguish the false positives from genuine planets. We also discuss the prospects for follow-up observations to measure the masses and atmospheres of the TESS planets.

• The paper employs Monte Carlo simulations to forecast approximately 1700 TESS exoplanet detections while quantifying astrophysical false positives from eclipsing binaries.
• It finds that TESS can detect numerous terrestrial-sized planets orbiting bright stars, making them ideal candidates for spectroscopic follow-up.
• The study underscores the critical role of complementary ground-based observations and precise photometry in reliably distinguishing genuine transits from false positives.

Overview of "The Transiting Exoplanet Survey Satellite: Simulations of Planet Detections and Astrophysical False Positives"

The Transiting Exoplanet Survey Satellite (TESS) is a mission conceptualized to conduct a wide-field survey dedicated to identifying exoplanets by monitoring their transits across bright host stars. The paper presented by Sullivan et al. employs Monte Carlo simulations to forecast the properties of transiting planets TESS might detect and to anticipate the instances of astrophysical false positives such as eclipsing binary stars. By leveraging existing data on stars and the occurrence rates of planets near the Earth, the paper models expectations for TESS's performance post-deployment.

The simulations predict that TESS will identify approximately 1700 transiting exoplanets from a set of 200,000 pre-selected target stars. These predictions include a significant number of terrestrial-sized planets (with radii less than twice that of Earth) hosted by both M dwarf stars and FGK dwarf stars. Of the planets smaller than twice Earth's size, a portion is expected to orbit stars brighter than K_s = 9, making them valuable targets for follow-up observations. The paper also calculates the expected number of planets within or near habitable zones and provides an estimate of the false positives TESS must contend with.

Numerical Results and Implications

The simulated detections reveal that TESS will likely find numerous small or terrestrial-sized exoplanets, with strong potential for discovering planets within habitable zones of their stars. Particularly noteworthy is the anticipated discovery of planets around stars bright enough for detailed follow-up observations. These bright host stars are crucial because they allow for the precise measurement of planetary characteristics such as mass and atmospheric composition using spectroscopy.

Moreover, simulations highlight over one thousand potential astrophysical false positives, primarily resulting from background or hierarchical eclipsing binary star systems. This prediction underscores the necessity of employing both TESS data and complementary ground-based observations to effectively differentiate genuine exoplanet detections from various types of false positives.

Technical Considerations and Future Work

The TESS mission employs four cameras capable of capturing wide field images approximately every 2 seconds, later integrated into two-minute data stacks for pre-selected stars, and thirty-minute full-frame images covering broader sections of the sky. The choice of which stars to observe at higher cadences (two minutes) is crucial, as the large volume of data captured makes it impractical to downlink the entirety of full-frame images for comprehensive paper.

Significant emphasis is placed on photometric precision, affected by potential noise sources, including zodiacal light and cosmic ray interference, as well as the mission-specific constraints such as pixel size and spacecraft pointing jitter. The authors apply a rigorous simulated approach to assess how these factors will interact and define the signal-to-noise ratio threshold necessary for reliable transit detection.

Concluding Remarks

The paper by Sullivan et al. sets robust expectations for the TESS mission's output, balancing prospects for impactful discoveries against challenges related to data quality and false-positive discrimination. By providing a framework to anticipate TESS's yield, this paper proves invaluable for planning future follow-up campaigns and for informing the methodologies required to interpret TESS data effectively. The mission's anticipated success at discovering planets around bright stars also potentially opens new avenues in exoplanet atmospheric studies, crucial for advancing our understanding of potentially habitable worlds beyond our solar system.