Planet Detection Simulations for Several Possible TESS Extended Missions

Planet Detection Simulations for Several Possible TESS Extended Missions

Authors:

Bouma et al

Abstract:
The Transiting Exoplanet Survey Satellite (TESS) will perform a two-year survey of nearly the entire sky, with the main goal of detecting exoplanets smaller than Neptune around bright and nearby stars. There do not appear to be any fundamental obstacles to continuing science operations for at least several years after the two-year Primary Mission. To provide a head start to those who will plan and propose for such a mission, we present simulations of exoplanet detections in a third year of TESS operations. Our goal is to provide a helpful reference for the exoplanet-related aspects of any Extended Mission, while recognizing this will be only one part of a larger community discussion of the scientific goals. We use Monte Carlo simulations to try and anticipate the quantities and types of planets that would be detected in each of 6 plausible scenarios for a one-year Extended Mission following the two-year Primary Mission. We find that: (1) there is no sharp fall-off in the planet discovery rate in the third year; (2) the quantity of newly detected sub-Neptune radius planets does not depend strongly on the schedule of pointings; (3) an important function of an Extended Mission would be improving our ability to predict the times of future transits and occultations of TESS-detected planets.

The asteroseismic potential of TESS: exoplanet-host stars

The asteroseismic potential of TESS: exoplanet-host stars

Authors:

Campante et al

Abstract:

New insights on stellar evolution and stellar interiors physics are being made possible by asteroseismology. Throughout the course of the Kepler mission, asteroseismology has also played an important role in the characterization of exoplanet-host stars and their planetary systems. The upcoming NASA Transiting Exoplanet Survey Satellite (TESS) will be performing a near all-sky survey for planets that transit bright nearby stars. In addition, its excellent photometric precision, combined with its fine time sampling and long intervals of uninterrupted observations, will enable asteroseismology of solar-type and red-giant stars. Here we develop a simple test to estimate the detectability of solar-like oscillations in TESS photometry of any given star. Based on an all-sky stellar and planetary synthetic population, we go on to predict the asteroseismic yield of the TESS mission, placing emphasis on the yield of exoplanet-host stars for which we expect to detect solar-like oscillations. This is done for both the target stars (observed at a 2-min cadence) and the full-frame-image stars (observed at a 30-min cadence). A similar exercise is also conducted based on a compilation of known host stars. We predict that TESS will detect solar-like oscillations in a few dozen target hosts (mainly subgiant stars but also in a smaller number of F dwarfs), in up to 200 low-luminosity red-giant hosts, and in over 100 solar-type and red-giant known hosts, thereby leading to a threefold improvement in the asteroseismic yield of exoplanet-host stars when compared to Kepler's.

Combining Photometry From Kepler and TESS to Improve Short-Period Exoplanet Characterization

Combining Photometry From Kepler and TESS to Improve Short-Period Exoplanet Characterization

Authors:

Placek et al

Abstract:

Planets emit thermal radiation and reflect incident light that they recieve from their host stars. As a planet orbits it's host star the photometric variations associated with these two effects produce very similar phase curves. If observed through only a single bandpass this leads to a degeneracy between certain planetary parameters that hinder the precise characterization of such planets. However, observing the same planet through two different bandpasses gives one much more information about the planet. Here, we develop a Bayesian methodology for combining photometry from both \emph{Kepler} and the Transiting Exoplanet Survey Satellite (TESS). In addition, we demonstrate via simulations that one can disentangle the reflected and thermally emitted light from the atmosphere of a hot-Jupiter as well as more precisely constrain both the geometric albedo and dayside temperature of the planet. This methodology can further be employed using various combinations of photometry from the James Webb Space Telescope (JWST), the Characterizing ExOplanet Satellite (CHEOPS), or the PLATO mission.

The Seager and Drake Equations and Their Interrelatedness

Statistical Drake–Seager Equation for exoplanet and SETI searches

Author:

Maccione

Abstract:

In 2013, MIT astrophysicist Sara Seager introduced what is now called the Seager Equation: it expresses the number N of exoplanets with detectable signs of life as the product of six factors: Ns=the number of stars observed, fQ=the fraction of stars that are quiet, fHZ=the fraction of stars with rocky planets in the Habitable Zone, fO=the fraction of those planets that can be observed, fL=the fraction that have life, fS=the fraction on which life produces a detectable signature gas. This we call the “classical Seager equation”.

Now suppose that each input of that equation is a positive random variable, rather than a sheer positive number. As such, each input random variable has a positive mean value and a positive variance that we assume to be numerically known by scientists. This we call the “Statistical Seager Equation”. Taking the logs of both sides of the Statistical Seager Equation, the latter is converted into an equation of the type log(N)=SUM of independent random variables.

Let us now consider the possibility that, in the future, the number of physical inputs considered by Seager when she proposed her equation will actually increase, since scientists will know more and more details about the astrophysics of exoplanets. In the limit for an infinite number of inputs, i.e. an infinite number of independent input random variables, the Central Limit Theorem (CLT) of Statistics applies to the Statistical Seager Equation. Thus, the probability density function (pdf) of the output random variable log(N) will approach a Gaussian (normal) distribution in the limit, whatever the distribution of the input random variables might possibly be. But if log(N) approaches the normal distribution, then N approaches the lognormal distribution, whose mean value is the sum of the input mean values and whose variance is the sum of the input variances.

This is just what this author realized back in 2008 when he transformed the Classical Drake Equation into the Statistical Drake Equation. This discovery led to much more related work in the following years.

In this paper we study the lognormal properties of the Statistical Seager Equation relating them to the present and future knowledge for exoplanets searches from both the ground and space.

TESS: the Potential for False Positive Exoplanet Detections

The Transiting Exoplanet Survey Satellite: Simulations of planet detections and astrophysical false positives

Authors:

Sullivan et al

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 less than 2 R_Earth planets will have host stars brighter than K = 9. Approximately 48 of the planets with R less than 2 R_Earth lie within or near the habitable zone (0.2 less than S/S_Earth less than 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_Earth. Additional planets larger than 2 R_Earth 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.

Multiple Stellar Systems can Screw up Transit Detection of Exoplanet Radius

Understanding The Effects Of Stellar Multiplicity On The Derived Planet Radii From Transit Surveys: Implications for Kepler, K2, and TESS

Authors:

Ciardi et al

Abstract:

We present a study on the effect of undetected stellar companions on the derived planetary radii for the Kepler Objects of Interest (KOIs). The current production of the KOI list assumes that the each KOI is a single star. Not accounting for stellar multiplicity statistically biases the planets towards smaller radii. The bias towards smaller radii depends on the properties of the companion stars and whether the planets orbit the primary or the companion stars. Defining a planetary radius correction factor XR, we find that if the KOIs are assumed to be single, then, {\it on average}, the planetary radii may be underestimated by a factor of ⟨XR⟩≈1.5. If typical radial velocity and high resolution imaging observations are performed and no companions are detected, this factor reduces to ⟨XR⟩≈1.2. The correction factor ⟨XR⟩ is dependent upon the primary star properties and ranges from ⟨XR⟩≈1.6 for A and F stars to ⟨XR⟩≈1.2 for K and M stars. For missions like K2 and TESS where the stars may be closer than the stars in the Kepler target sample, observational vetting (primary imaging) reduces the radius correction factor to ⟨XR⟩≈1.1. Finally, we show that if the stellar multiplicity rates are not accounted for correctly, occurrence rate calculations for Earth-sized planets may overestimate the frequency of small planets by as much as 15−20\%.

Characterizing Transiting ExoPlanet Atmospheres through 2025

Characterizing Transiting Planet Atmospheres through 2025

Authors:

Cowan et al

Abstract:

We have only been able to comprehensively characterize the atmospheres of a handful of transiting planets, because most orbit faint stars. TESS will discover transiting planets orbiting the brightest stars, enabling, in principle, an atmospheric survey of 10^2 to 10^3 bright hot Jupiters and warm sub-Neptunes. Uniform observations of such a statistically significant sample would provide leverage to understand---and learn from---the diversity of short-period planets. We argue that the best way to maximize the scientific returns of TESS is with a follow-up space mission consisting of a ~1 m telescope with an optical--NIR spectrograph: it could measure molecular absorption for non-terrestrial planets, as well as eclipses and phase variations for the hottest jovians. Such a mission could observe up to 10^3 transits per year, thus enabling it to survey a large fraction of the bright (J less than 11) TESS planets. JWST could be used to perform detailed atmospheric characterization of the most interesting transiting targets (transit, eclipse, and---when possible---phase-resolved spectroscopy). TESS is also expected to discover a few temperate terrestrial planets transiting nearby M-Dwarfs. Characterizing these worlds will be time-intensive: JWST will need months to provide tantalizing constraints on the presence of an atmosphere, planetary rotational state, clouds, and greenhouse gases. Future flagship missions should be designed to provide better constraints on the habitability of M-Dwarf temperate terrestrial planets.

Multiple Star Systems Observed with CoRoT and Kepler

Multiple star systems observed with CoRoT and Kepler (invited review)

Author:

Southworth

Abstract:

The CoRoT and Kepler satellites were the first space platforms designed to perform high-precision photometry for a large number of stars. Multiple systems display a wide variety of photometric variability, making them natural benefactors of these missions. I review the work arising from CoRoT and Kepler observations of multiple systems, with particular emphasis on eclipsing binaries containing giant stars, pulsators, triple eclipses and/or low-mass stars. Many more results remain untapped in the data archives of these missions, and the future holds the promise of K2, TESS and PLATO.

The K2-TESS Stellar Properties Catalog

The K2-TESS Stellar Properties Catalog

Authors:

Stassun et al

Abstract:

We introduce a catalog of stellar properties for stars observed by the Kepler follow-on mission, K2. We base the catalog on a cross-match between the K2 Campaign target lists and the current working version of the NASA TESS target catalog. The resulting K2-TESS Stellar Properties Catalog includes value-added information from the TESS Target Catalog, including stellar colors, proper motions, and an estimated luminosity class (dwarf/subgiant versus giant) for each star based on a reduced-proper-motion criterion. Also included is the Guest Observer program identification number(s) associated with each K2 target. The K2-TESS Stellar Properties Catalog is available to the community as a freely accessible data portal on the Filtergraph system at: this http URL .

The EB Factory Project

The EB Factory Project. II. Validation with the Kepler Field in Preparation for K2 and TESS

Authors:

Parvizi et al

Abstract:

Large repositories of high precision light curve data, such as the Kepler data set, provide the opportunity to identify astrophysically important eclipsing binary (EB) systems in large quantities. However, the rate of classical "by eye" human analysis restricts complete and efficient mining of EBs from these data using classical techniques. To prepare for mining EBs from the upcoming K2 mission as well as other current missions, we developed an automated end-to-end computational pipeline - the Eclipsing Binary Factory (EBF) - that automatically identifies EBs and classifies them into morphological types. The EBF has been previously tested on ground-based light curves. To assess the performance of the EBF in the context of space-based data, we apply the EBF to the full set of light curves in the Kepler "Q3" Data Release. We compare the EBs identified from this automated approach against the human generated Kepler EB Catalog of ~2,600 EBs. When we require EB classification with at least 90% confidence, we find that the EBF correctly identifies and classifies eclipsing contact (EC), eclipsing semi-detached (ESD), and eclipsing detached (ED) systems with a false positive rate of only 4%, 4%, and 8%, while complete to 64%, 46%, and 32% respectively. When classification confidence is relaxed, the EBF identifies and classifies ECs, ESDs, and EDs with a slightly higher false positive rate of 6%, 16%, and 8%, while much more complete to 86%, 74%, and 62% respectively. Through our processing of the entire Kepler "Q3" dataset, we also identify 68 new candidate EBs that may have been missed by the human generated Kepler EB Catalog. We discuss the EBF's potential application to light curve classification for periodic variable stars more generally for current and upcoming surveys like K2 and the Transiting Exoplanet Survey Satellite.

The Transiting Exoplanet Survey Satellite

The Transiting Exoplanet Survey Satellite

Authors:

Ricker et al

Abstract:

he Transiting Exoplanet Survey Satellite (TESS) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its two-year mission, TESS will employ four wide-field optical CCD cameras to monitor at least 200,000 main-sequence dwarf stars with I less than 13 for temporary drops in brightness caused by planetary transits. Each star will be observed for an interval ranging from one month to one year, depending mainly on the star's ecliptic latitude. The longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the James Webb Space Telescope. Brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. TESS stars will be 10-100 times brighter than those surveyed by the pioneering Kepler mission. This will make TESS planets easier to characterize with follow-up observations. TESS is expected to find more than a thousand planets smaller than Neptune, including dozens that are comparable in size to the Earth. Public data releases will occur every four months, inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations.