Detecting Solar System Analogs through Joint Radial Velocity/Astrometric Surveys

Earth-mass exoplanets on year-long orbits and cool gas giants (CGG) on decade-long orbits lie at the edge of current detection limits. The Terra Hunting Experiment (THE) will take nightly radial velocity (RV) observations on HARPS3 of at least 40 bright nearby G and K dwarfs for 10 years, with a target 1$\sigma$ measurement error of $\sim$0.3 m/s, in search of exoplanets that are Earth-like in mass and temperature. However, RV observations can only provide minimum mass estimates, due to the mass-inclination degeneracy. Astrometric observations of these same stars, with sufficient precision, could break this degeneracy. Gaia will soon release $\sim$100-200 astrometric observations of the THE stars with a 10 year baseline and $\sim$34.2 $\mu$as 1$\sigma$ along-scan measurement error. The Nancy Grace Roman Space Telescope will be capable of precision astrometry using its wide field imager (target $\sim$5-20 $\mu$as 1$\sigma$ measurement error for bright stars) and could extend the astrometric observational baseline to $\sim$25 years. We simulate and model an observing program that combines data from these three telescopes. We find that (1) THE RVs and Gaia astrometry can detect Earth-like and CGG-like exoplanets around bright Sun-like stars at 10 parsecs and that (2) adding Roman astrometry improves the detection precision for CGG masses and periods by a factor up to $\sim$10 and $\sim$4, respectively. Such a survey could provide insight into the prevalence of Solar System analogs, exoplanet architectures reminiscent of the mass and orbital separation hierarchy of our Solar System, for the nearest Sun-like stars.Comment: 21 pages, 10 figures. Revised based on comments from anonymous reviewer at AAS Journals. Code available at https://github.com/dyahalomi/rv_and_astrometr

The Mass of the White Dwarf Companion in the Self-Lensing Binary KOI-3278: Einstein vs. Newton

KOI-3278 is a self-lensing stellar binary consisting of a white-dwarf secondary orbiting a Sun-like primary star. Kruse and Agol (2014) noticed small periodic brightenings every 88.18 days in the Kepler photometry and interpreted these as the result of microlensing by a white dwarf with about 63$\%$ of the mass of the Sun. We obtained two sets of spectra for the primary that allowed us to derive three sets of spectroscopic estimates for its effective temperature, surface gravity, and metallicity for the first time. We used these values to update the Kruse and Agol (2014) Einsteinian microlensing model, resulting in a revised mass for the white dwarf of $0.539^{+0.022}_{-0.020} \, M_{\odot}$. The spectra also allowed us to determine radial velocities and derive orbital solutions, with good agreement between the two independent data sets. An independent Newtonian dynamical MCMC model of the combined velocities yielded a mass for the white dwarf of $0.5122^{+0.0057}_{-0.0058} \, M_{\odot}$. The nominal uncertainty for the Newtonian mass is about four times better than for the Einsteinian, $\pm 1.1\%$ vs. $\pm 4.1\%$ and the difference between the two mass determinations is $5.2 \%$. We then present a joint Einsteinian microlensing and Newtonian radial velocity model for KOI-3278, which yielded a mass for the white dwarf of $0.5250^{+0.0082}_{-0.0089} \, M_{\odot}$. This joint model does not rely on any white dwarf evolutionary models or assumptions on the white dwarf mass-radius relation. We discuss the benefits of a joint model of self-lensing binaries, and how future studies of these systems can provide insight into the mass-radius relation of white dwarfs.Comment: ApJ Accepted; 22 Pages, 8 Figures, 6 Tables and 4 Supplementary Table

Not So Fast Kepler-1513: A Perturbing Planetary Interloper in the Exomoon Corridor

Transit Timing Variations (TTVs) can be induced by a range of physical phenomena, including planet-planet interactions, planet-moon interactions, and stellar activity. Recent work has shown that roughly half of moons would induce fast TTVs with a short period in the range of two-to-four orbits of its host planet around the star. An investigation of the Kepler TTV data in this period range identified one primary target of interest, Kepler-1513 b. Kepler-1513 b is a $8.05^{+0.58}_{-0.40}$ $R_\oplus$ planet orbiting a late G-type dwarf at $0.53^{+0.04}_{-0.03}$ AU. Using Kepler photometry, this initial analysis showed that Kepler-1513 b's TTVs were consistent with a moon. Here, we report photometric observations of two additional transits nearly a decade after the last Kepler transit using both ground-based observations and space-based photometry with TESS. These new transit observations introduce a previously undetected long period TTV, in addition to the original short period TTV signal. Using the complete transit dataset, we investigate whether a non-transiting planet, a moon, or stellar activity could induce the observed TTVs. We find that only a non-transiting perturbing planet can reproduce the observed TTVs. We additionally perform transit origami on the Kepler photometry, which independently applies pressure against a moon hypothesis. Specifically, we find that Kepler-1513 b's TTVs are consistent with an exterior non-transiting $\sim$Saturn mass planet, Kepler-1513 c, on a wide orbit, $\sim$5$\%$ outside a 5:1 period ratio with Kepler-1513 b. This example introduces a previously unidentified cause for planetary interlopers in the exomoon corridor, namely an insufficient baseline of observations.Comment: 20 pages, 13 figures. Accepted to MNRAS. Code available at https://github.com/dyahalomi/Kepler151

TOI-132 b: A short-period planet in the Neptune desert transiting a V=11.3 G-type star

The Neptune desert is a feature seen in the radius-period plane, whereby a notable dearth of short period, Neptune-like planets is found. Here, we report the Transiting Exoplanet Survey Satellite (TESS) discovery of a new short-period planet in the Neptune desert, orbiting the G-type dwarf TYC 8003-1117-1 (TOI-132). TESS photometry shows transit-like dips at the level of similar to 1400 ppm occurring every similar to 2.11 d. High-precision radial velocity follow-up with High Accuracy Radial Velocity Planet Searcher confirmed the planetary nature of the transit signal and provided a semi-amplitude radial velocity variation of 11.38(-0.85)(+0.84) m s(-1), which, when combined with the stellar mass of 0.97 +/- 0.06 M-circle dot, provides a planetary mass of 22.40(-1.92)(+1.90) M-circle plus. Modelling the TESS light curve returns a planet radius of 3.42(-0.14)(+0.13) R-circle plus , and therefore the planet bulk density is found to be 3.08(-0.46)(+0.44) g cm(-3). Planet structure models suggest that the bulk of the planet mass is in the form of a rocky core, with an atmospheric mass fraction of 4.3(-2.3)(+1.2) percent. TOI-132 b is a TESS Level 1 Science Requirement candidate, and therefore priority follow-up will allow the search for additional planets in the system, whilst helping to constrain low-mass planet formation and evolution models, particularly valuable for better understanding of the Neptune desert

The Magellan-TESS Survey I: Survey Description and Mid-Survey Results

One of the most significant revelations from Kepler is that roughly one-third of Sun-like stars host planets which orbit their stars within 100 days and are between the size of Earth and Neptune. How do these super-Earth and sub-Neptune planets form, what are they made of, and do they represent a continuous population or naturally divide into separate groups? Measuring their masses and thus bulk densities can help address these questions of their origin and composition. To that end, we began the Magellan-TESS Survey (MTS), which uses Magellan II/PFS to obtain radial velocity (RV) masses of 30 transiting exoplanets discovered by TESS and develops an analysis framework that connects observed planet distributions to underlying populations. In the past, RV measurements of small planets have been challenging to obtain due to the faintness and low RV semi-amplitudes of most Kepler systems, and challenging to interpret due to the potential biases in the existing ensemble of small planet masses from non-algorithmic decisions for target selection and observation plans. The MTS attempts to minimize these biases by focusing on bright TESS targets and employing a quantitative selection function and multi-year observing strategy. In this paper, we (1) describe the motivation and survey strategy behind the MTS, (2) present our first catalog of planet mass and density constraints for 25 TESS Objects of Interest (TOIs; 20 in our population analysis sample, five that are members of the same systems), and (3) employ a hierarchical Bayesian model to produce preliminary constraints on the mass-radius (M-R) relation. We find qualitative agreement with prior mass-radius relations but some quantitative differences (abridged). The the results of this work can inform more detailed studies of individual systems and offer a framework that can be applied to future RV surveys with the goal of population inferences.Comment: 101 pages (39 of main text and references, the rest an appendix of figures and tables). Submitted to AAS Journal

An Eccentric Massive Jupiter Orbiting a Subgiant on a 9.5-day Period Discovered in the <i>Transiting Exoplanet Survey Satellite</i> Full Frame Images

We report the discovery of TOI-172 b from the Transiting Exoplanet Survey Satellite (TESS) mission, a massive hot Jupiter transiting a slightly evolved G star with a 9.48-day orbital period. This is the first planet to be confirmed from analysis of only the TESS full frame images, because the host star was not chosen as a two-minute cadence target. From a global analysis of the TESS photometry and follow-up observations carried out by the TESS Follow-up Observing Program Working Group, TOI-172 (TIC 29857954) is a slightly evolved star with an effective temperature of T eff = 5645 ± 50 K, a mass of M ⋆ = {1.128}-0.061+0.065 M ⊙, radius of R ⋆ = {1.777}-0.044+0.047 R ⊙, a surface gravity of log g ⋆ = {3.993}-0.028+0.027, and an age of {7.4}-1.5+1.6 {Gyr}. Its planetary companion (TOI-172 b) has a radius of R P = {0.965}-0.029+0.032 R J, a mass of M P = {5.42}-0.20+0.22 M J, and is on an eccentric orbit (e={0.3806}-0.0090+0.0093). TOI-172 b is one of the few known massive giant planets on a highly eccentric short-period orbit. Future study of the atmosphere of this planet and its system architecture offer opportunities to understand the formation and evolution of similar systems

Two Massive Jupiters in Eccentric Orbits from the TESS Full-frame Images

We report the discovery of two short-period massive giant planets from NASA's Transiting Exoplanet Survey Satellite (TESS). Both systems, TOI-558 (TIC 207110080) and TOI-559 (TIC 209459275), were identified from the 30 minute cadence full-frame images and confirmed using ground-based photometric and spectroscopic followup observations from TESS's follow-up observing program working group. We find that TOI-558 b, which transits an F-dwarf (M-* =1.349(-0.065)(+0.064) M-circle dot, R-* =1.496(-0.040)(+0.042) R-circle dot, T-eff = 6466(-93)(+95) K, age 1.79(-0.73)(+0.91) Gyr) with an orbital period of 14.574 days, has a mass of 3.61 +/- 0.15 M-J, a radius of 1.086(-0.038)(+0.041) R-J, and an eccentric (e = 0.300(-0.020)(+0.022)) orbit. TOI-559 b transits a G dwarf (M-* = 1.026 +/- 0.057 M-circle dot, R-* =1.233(-0.026)(+0.028) R-circle dot, T-eff = 5925(-76)(+85) K, age 6.8(-2.0)(+2.5) Gyr) in an eccentric (e = 0.151 +/- 0.011) 6.984 days orbit with a mass of 6.01(-0.23)(+0.24) M-J and a radius of 1.091(-0.025+)(0.028) R-J. Our spectroscopic follow up also reveals a long-term radial velocity trend for TOI-559, indicating a long-period companion. The statistically significant orbital eccentricity measured for each system suggests that these planets migrated to their current location through dynamical interactions. Interestingly, both planets are also massive (>3 M-J), adding to the population of massive giant planets identified by TESS. Prompted by these new detections of high-mass planets, we analyzed the known mass distribution of hot and warm Jupiters but find no significant evidence for multiple populations. TESS should provide a near magnitude-limited sample of transiting hot Jupiters, allowing for future detailed population studies

The TESS Objects of Interest Catalog from the TESS Prime Mission

We present 2241 exoplanet candidates identified with data from the Transiting Exoplanet Survey Satellite (TESS) during its 2 yr Prime Mission. We list these candidates in the TESS Objects of Interest (TOI) Catalog, which includes both new planet candidates found by TESS and previously known planets recovered by TESS observations. We describe the process used to identify TOIs, investigate the characteristics of the new planet candidates, and discuss some notable TESS planet discoveries. The TOI catalog includes an unprecedented number of small planet candidates around nearby bright stars, which are well suited for detailed follow-up observations. The TESS data products for the Prime Mission (sectors 1-26), including the TOI catalog, light curves, full-frame images, and target pixel files, are publicly available at the Mikulski Archive for Space Telescopes

A Possible Alignment Between the Orbits of Planetary Systems and their Visual Binary Companions

Astronomers do not have a complete picture of the effects of wide-binary companions (semimajor axes greater than 100 au) on the formation and evolution of exoplanets. We investigate these effects using new data from Gaia Early Data Release 3 and the Transiting Exoplanet Survey Satellite mission to characterize wide-binary systems with transiting exoplanets. We identify a sample of 67 systems of transiting exoplanet candidates (with well-determined, edge-on orbital inclinations) that reside in wide visual binary systems. We derive limits on orbital parameters for the wide-binary systems and measure the minimum difference in orbital inclination between the binary and planet orbits. We determine that there is statistically significant difference in the inclination distribution of wide-binary systems with transiting planets compared to a control sample, with the probability that the two distributions are the same being 0.0037. This implies that there is an overabundance of planets in binary systems whose orbits are aligned with those of the binary. The overabundance of aligned systems appears to primarily have semimajor axes less than 700 au. We investigate some effects that could cause the alignment and conclude that a torque caused by a misaligned binary companion on the protoplanetary disk is the most promising explanation