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Addison, B. C., Wright, D. J., Nicholson, B. A., Cale, B., Mocnik, T., Huber, D., et al. (2021). TOI-257b (HD 19916b): a warm sub-saturn orbiting an evolved F-type star. Mon. Not. Roy. Astron. Soc., 502(3), 3704–3722.
Abstract: We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA's Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the MINERVA-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of M-P = 0.138 +/- 0.023M(J) (43.9 +/- 7.3 M-circle plus), a radius of R-P = 0.639 +/- 0.013 R-J (7.16 +/- 0.15 R-circle plus), bulk density of 0.65(-0.11)(+0.12) (cgs), and period 18.38818(-0.00084)(+0.00085) days. TOI-257b orbits a bright (V = 7.612 mag) somewhat evolved late F-type star with M-* = 1.390 +/- 0.046(Msun), R-* = 1.888 +/- 0.033 R-sun, T-eff = 6075 +/- 90 K, and vsin i = 11.3 +/- 0.5 kms(-1). Additionally, we find hints for a second non-transiting sub-Saturn mass planet on a similar to 71 day orbit using the radial velocity data. This system joins the ranks of a small number of exoplanet host stars (similar to 100) that have been characterized with asteroseismology. Warm sub-Saturns are rare in the known sample of exoplanets, and thus the discovery of TOI-257b is important in the context of future work studying the formation and migration history of similar planetary systems.
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Astudillo-Defru, N., Cloutier, R., Wang, S. X., Teske, J., Brahm, R., Hellier, C., et al. (2020). A hot terrestrial planet orbiting the bright M dwarf L 168-9 unveiled by TESS. Astron. Astrophys., 636, 13 pp.
Abstract: We report the detection of a transiting super-Earth-sized planet (R = 1.39 +/- 0.09 R-circle plus) in a 1.4-day orbit around L 168-9 (TOI-134), a bright M1V dwarf (V = 11, K = 7.1) located at 25.15 +/- 0.02 pc. The host star was observed in the first sector of the Transiting Exoplanet Survey Satellite (TESS) mission. For confirmation and planet mass measurement purposes, this was followed up with ground-based photometry, seeing-limited and high-resolution imaging, and precise radial velocity (PRV) observations using the HARPS and Magellan/PFS spectrographs. By combining the TESS data and PRV observations, we find the mass of L 168-9 b to be 4.60 +/- 0.56 M-circle plus and thus the bulk density to be 1.74(-0.33)(+0.44) times higher than that of the Earth. The orbital eccentricity is smaller than 0.21 (95% confidence). This planet is a level one candidate for the TESS mission's scientific objective of measuring the masses of 50 small planets, and it is one of the most observationally accessible terrestrial planets for future atmospheric characterization.
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Bouma, L. G., Hartman, J. D., Brahm, R., Evans, P., Collins, K. A., Zhou, G., et al. (2020). Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602. Astron. J., 160(5), 20 pp.
Abstract: We report the discovery of TOI 837b and its validation as a transiting planet. We characterize the system using data from the NASA Transiting Exoplanet Survey Satellite mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI 837 is a T = 9.9 mag G0/F9 dwarf in the southern open cluster IC 2602. The star and planet are therefore 35(-5)(+11) million years old. Combining the transit photometry with a prior on the stellar parameters derived from the cluster color-magnitude diagram, we find that the planet has an orbital period of 8.3 days and is slightly smaller than Jupiter (R-p = 0.77(0.07)(+0.09) R-Jup). From radial velocity monitoring, we limit M-p sin i to less than 1.20 M-Jup (3 sigma). The transits either graze or nearly graze the stellar limb. Grazing transits are a cause for concern, as they are often indicative of astrophysical false-positive scenarios. Our follow-up data show that such scenarios are unlikely. Our combined multicolor photometry, high-resolution imaging, and radial velocities rule out hierarchical eclipsing binary scenarios. Background eclipsing binary scenarios, though limited by speckle imaging, remain a 0.2% possibility. TOI 837b is therefore a validated adolescent exoplanet. The planetary nature of the system can be confirmed or refuted through observations of the stellar obliquity and the planetary mass. Such observations may also improve our understanding of how the physical and orbital properties of exoplanets change in time.
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Brahm, R., Nielsen, L. D., Wittenmyer, R. A., Wang, S. H., Rodriguez, J. E., Espinoza, N., et al. (2020). TOI-481 b and TOI-892 b: Two Long-period Hot Jupiters from the Transiting Exoplanet Survey Satellite. Astron. J., 160(5), 14 pp.
Abstract: We present the discovery of two new 10 day period giant planets from the Transiting Exoplanet Survey Satellite mission, whose masses were precisely determined using a wide diversity of ground-based facilities. TOI-481.b and TOI-892.b have similar radii (0.99.+/-.0.01 R-J and 1.07.+/-.0.02 R-J, respectively), and orbital periods (10.3311 days and 10.6266 days, respectively), but significantly different masses (1.53.+/-.0.03 MJ versus 0.95.+/-.0.07 MJ, respectively). Both planets orbit metal-rich stars ([Fe H] = + 0.26. 0.05 dex and [Fe H] = +0.24. 0.05 for TOI-481 and TOI-892, respectively) but at different evolutionary stages. TOI-481 is a M*=.1.14.+/-.0.02 M., R*=.1.66.+/-.0.02 R. G-type star (T-eff = 5735 +/- 72 K), that with an age of 6.7 Gyr, is in the turn-off point of the main sequence. TOI-892 on the other hand, is a F-type dwarf star (T-eff = 6261 +/- 80 K), which has a mass of M*=.1.28.+/-.0.03 M-circle dot and a radius of R*=.1.39.+/-.0.02 R-circle dot. TOI-481.b and TOI-892.b join the scarcely populated region of transiting gas giants with orbital periods longer than 10 days, which is important to constrain theories of the formation and structure of hot Jupiters.
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Brahm, R., Ulmer-Moll, S., Hobson, M. J., Jordan, A., Henning, T., Trifonov, T., et al. (2023). Three Long-period Transiting Giant Planets from TESS. Astron. J., 165(6), 227.
Abstract: We report the discovery and orbital characterization of three new transiting warm giant planets. These systems were initially identified as presenting single-transit events in the light curves generated from the full-frame images of the Transiting Exoplanet Survey Satellite. Follow-up radial velocity measurements and additional light curves were used to determine the orbital periods and confirm the planetary nature of the candidates. The planets orbit slightly metal-rich late F- and early G-type stars. We find that TOI 4406b has a mass of M ( P ) = 0.30 +/- 0.04 M (J), a radius of R ( P ) = 1.00 +/- 0.02 R (J), and a low-eccentricity orbit (e = 0.15 +/- 0.05) with a period of P = 30.08364 +/- 0.00005 days. TOI 2338b has a mass of M ( P ) = 5.98 +/- 0.20 M (J), a radius of R ( P ) = 1.00 +/- 0.01 R (J), and a highly eccentric orbit (e = 0.676 +/- 0.002) with a period of P = 22.65398 +/- 0.00002 days. Finally, TOI 2589b has a mass of M ( P ) = 3.50 +/- 0.10 M (J), a radius of R ( P ) = 1.08 +/- 0.03 R (J), and an eccentric orbit (e = 0.522 +/- 0.006) with a period of P = 61.6277 +/- 0.0002 days. TOI 4406b and TOI 2338b are enriched in metals compared to their host stars, while the structure of TOI 2589b is consistent with having similar metal enrichment to its host star.
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Carleo, I., Gandolfi, D., Barragan, O., Livingston, J. H., Persson, C. M., Lam, K. W. F., et al. (2020). The Multiplanet System TOI-421*. Astron. J., 160(3), 23 pp.
Abstract: We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V = 9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations-comprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed Echelle Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution echelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurements-and confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421 b, has an orbital period of P-b = 5.19672 +/- 0.00049 days, a mass of M-b = 7.17 +/- 0.66 M-circle plus, and a radius of R-b = R-circle plus, whereas the outer warm Neptune, TOI-421 c, has a period of P-c = 16.06819 +/- 0.00035 days, a mass of M-c = 16.42(-1.04)(+1.06)M(circle plus), a radius of R-c = 5.09(-0.15)(+0.16)R(circle plus), and a density of rho(c) = 0.685(-0.072)(+0.080) cm(-3). With its characteristics, the outer planet (rho(c) = 0.685(-0.0072)(+0.080) cm(-3)) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421 b and TOI-421 c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Ly alpha transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH4 in the atmosphere of TOI-421 c if equilibrium chemistry is assumed.
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Clark, J. T., Addison, B. C., Okumura, J., Vach, S., Errico, A., Heitzmann, A., et al. (2023). Spinning up a Daze: TESS Uncovers a Hot Jupiter Orbiting the Rapid Rotator TOI-778. Astron. J., 165(5), 207.
Abstract: NASA's Transiting Exoplanet Survey Satellite (TESS) mission has been uncovering a growing number of exoplanets orbiting nearby, bright stars. Most exoplanets that have been discovered by TESS orbit narrow-line, slow-rotating stars, facilitating the confirmation and mass determination of these worlds. We present the discovery of a hot Jupiter orbiting a rapidly rotating (v sin (i) = 35.1 +/- 1.0 km s(-1) early F3V-dwarf, HD 115447 (TOI-778). The transit signal taken from Sectors 10 and 37 of TESS's initial detection of the exoplanet is combined with follow-up ground-based photometry and velocity measurements taken from MINERVA-Australis, TRES, CORALIE, and CHIRON to confirm and characterize TOI-778 b. A joint analysis of the light curves and the radial velocity measurements yields a mass, a radius, and an orbital period for TOI-778 b of 2.76(-0.23)(+0.24) M-J, 1.370 +/- 0.043 R-J, and similar to 4.63 days, respectively. The planet orbits a bright (V = 9.1 mag) F3-dwarf with M = 1.40 +/- 0.05 M-circle dot, R = 1.70 +/- 0.05 R-circle dot, and log g = 4.05 +/- 0.17. We observed a spectroscopic transit of TOI-778 b, which allowed us to derive a sky-projected spin-orbit angle of 18 degrees +/- 11 degrees, consistent with an aligned planetary system. This discovery demonstrates the capability of smaller-aperture telescopes such as MINERVA-Australis to detect the radial velocity signals produced by planets orbiting broad-line, rapidly rotating stars.
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Dawson, R. I., Huang, C. L. X., Brahm, R., Collins, K. A., Hobson, M. J., Jordan, A., et al. (2021). Precise Transit and Radial-velocity Characterization of a Resonant Pair: The Warm Jupiter TOI-216c and Eccentric Warm Neptune TOI-216b. Astron. J., 161(4), 161.
Abstract: TOI-216 hosts a pair of warm, large exoplanets discovered by the TESS mission. These planets were found to be in or near the 2:1 resonance, and both of them exhibit transit timing variations (TTVs). Precise characterization of the planets' masses and radii, orbital properties, and resonant behavior can test theories for the origins of planets orbiting close to their stars. Previous characterization of the system using the first six sectors of TESS data suffered from a degeneracy between planet mass and orbital eccentricity. Radial-velocity measurements using HARPS, FEROS, and the Planet Finder Spectrograph break that degeneracy, and an expanded TTV baseline from TESS and an ongoing ground-based transit observing campaign increase the precision of the mass and eccentricity measurements. We determine that TOI-216c is a warm Jupiter, TOI-216b is an eccentric warm Neptune, and that they librate in 2:1 resonance with a moderate libration amplitude of deg, a small but significant free eccentricity of for TOI-216b, and a small but significant mutual inclination of 12-39 (95% confidence interval). The libration amplitude, free eccentricity, and mutual inclination imply a disturbance of TOI-216b before or after resonance capture, perhaps by an undetected third planet.
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Dong, J. Y., Huang, C. X., Dawson, R. I., Foreman-Mackey, D., Collins, K. A., Quinn, S. N., et al. (2021). Warm Jupiters in TESS Full-frame Images: A Catalog and Observed Eccentricity Distribution for Year 1. Astrophys. J. Suppl. Ser., 255(1), 6.
Abstract: Warm Jupiters-defined here as planets larger than 6 Earth radii with orbital periods of 8-200 days-are a key missing piece in our understanding of how planetary systems form and evolve. It is currently debated whether Warm Jupiters form in situ, undergo disk or high-eccentricity tidal migration, or have a mixture of origin channels. These different classes of origin channels lead to different expectations for Warm Jupiters' properties, which are currently difficult to evaluate due to the small sample size. We take advantage of the Transiting Exoplanet Survey Satellite (TESS) survey and systematically search for Warm Jupiter candidates around main-sequence host stars brighter than the TESS-band magnitude of 12 in the full-frame images in Year 1 of the TESS Prime Mission data. We introduce a catalog of 55 Warm Jupiter candidates, including 19 candidates that were not originally released as TESS objects of interest by the TESS team. We fit their TESS light curves, characterize their eccentricities and transit-timing variations, and prioritize a list for ground-based follow-up and TESS Extended Mission observations. Using hierarchical Bayesian modeling, we find the preliminary eccentricity distributions of our Warm-Jupiter-candidate catalog using a beta distribution, a Rayleigh distribution, and a two-component Gaussian distribution as the functional forms of the eccentricity distribution. Additional follow-up observations will be required to clean the sample of false positives for a full statistical study, derive the orbital solutions to break the eccentricity degeneracy, and provide mass measurements.
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Hartman, J. D., Bakos, G. A., Csubry, Z., Howard, A. W., Isaacson, H., Giacalone, S., et al. (2023). TOI 4201 b and TOI 5344 b: Discovery of Two Transiting Giant Planets around M-dwarf Stars and Revised Parameters for Three Others. Astron. J., 166(4), 163.
Abstract: We present the discovery from the TESS mission of two giant planets transiting M-dwarf stars: TOI 4201 b and TOI 5344 b. We also provide precise radial velocity measurements and updated system parameters for three other M dwarfs with transiting giant planets: TOI 519, TOI 3629, and TOI 3714. We measure planetary masses of 0.525 +/- 0.064 MJ, 0.243 +/- 0.020 M-J, 0.689 +/- 0.030 M-J, 2.57 +/- 0.15 M-J, and 0.412 +/- 0.040 M-J for TOI 519 b, TOI 3629 b, TOI 3714 b, TOI 4201 b, and TOI 5344 b, respectively. The corresponding stellar masses are 0.372 +/- 0.018 M-circle dot, 0.635 +/- 0.032 M-circle dot, 0.522 +/- 0.028 M-circle dot, 0.626 +/- 0.033 M-circle dot, and 0.612 +/- 0.034 M-circle dot. All five hosts have supersolar metallicities, providing further support for recent findings that, like for solar-type stars, close-in giant planets are preferentially found around metal-rich M-dwarf host stars. Finally, we describe a procedure for accounting for systematic errors in stellar evolution models when those models are included directly in fitting a transiting planet system.
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Hartman, J. D., Jordan, A., Bayliss, D., Bakos, G. A., Bento, J., Bhatti, W., et al. (2020). HATS-47b, HATS-48Ab, HATS-49b, and HATS-72b: Four Warm Giant Planets Transiting K Dwarfs. Astron. J., 159(4), 23 pp.
Abstract: We report the discovery of four transiting giant planets around K dwarfs. The planets HATS-47b, HATS-48Ab, HATS49b, and HATS-72b have masses of 0.369+ 0.0210.031MJ, 0.243+ 0.0300.022 MJ, 0.353+ 0.0270.038 MJ, and 0.1254. 0.0039 MJ, respectively, and radii of 1.117. 0.014 RJ, 0.800. 0.015 RJ, 0.765. 0.013 RJ, and 0.7224. 0.0032 RJ, respectively. The planets orbit close to their host stars with orbital periods of 3.9228 days, 3.1317 days, 4.1480 days, and 7.3279 days, respectively. The hosts are main-sequence K dwarfs with masses of 0.674+ 0.0120.016.M, 0.7279. 0.0066.M, 0.7133. 0.0075.M, and 0.7311. 0.0028, and with V-band magnitudes of V = 14.829. 0.010, 14.35. 0.11, 14.998. 0.040 and 12.469. 0.010. The super-Neptune HATS-72b (a.k.a. WASP-191b and TOI 294.01) was independently identified as a transiting planet candidate by the HATSouth, WASP, and TESS surveys, and we present a combined analysis of all of the data gathered by each of these projects (and their follow-up programs). An exceptionally precise mass is measured for HATS-72b thanks to high-precision radial velocity (RV) measurements obtained with VLT/ESPRESSO, FEROS, HARPS, and Magellan/PFS. We also incorporate TESS observations of the warm Saturn-hosting systems HATS-47 (a.k.a. TOI.1073.01), HATS-48A, and HATS-49. HATS-47 was independently identified as a candidate by the TESS team, while the other two systems were not previously identified from the TESS data. The RV orbital variations are measured for these systems using Magellan/PFS. HATS-48A has a resolved 5.. 4 neighbor in Gaia.DR2, which is a common-proper-motion binary star companion to HATS-48A with a mass of 0.22.M and a current projected physical separation of similar to 1400 au.
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Heitzmann, A., Zhou, G., Quinn, S. N., Huang, C. X., Dong, J. Y., Bouma, L. G., et al. (2023). TOI-4562b: A Highly Eccentric Temperate Jupiter Analog Orbiting a Young Field Star. Astron. J., 165(3), 121.
Abstract: We report the discovery of TOI-4562b (TIC-349576261), a Jovian planet orbiting a young F7V-type star, younger than the Praesepe/Hyades clusters (< 700 Myr). This planet stands out because of its unusually long orbital period for transiting planets with known masses (Porb = 225.11781(- 0.00022) (+0.00025 )days) and because it has a substantial eccentricity (e = 0.76(- 0.02) (+0.02)). The location of TOI-4562 near the southern continuous viewing zone of TESS allowed observations throughout 25 sectors, enabling an unambiguous period measurement from TESS alone. Alongside the four available TESS transits, we performed follow-up photometry using the South African Astronomical Observatory node of the Las Cumbres Observatory and spectroscopy with the CHIRON spectrograph on the 1.5 m SMARTS telescope. We measure a radius of 1.118 (+0.013) (-0.014) R(J )and a mass of 2.30(-0.47)(+0.48)M(J) for TOI-4562b. The radius of the planet is consistent with contraction models describing the early evolution of the size of giant planets. We detect tentative transit timing variations at the similar to 20 minutes level from five transit events, favoring the presence of a companion that could explain the dynamical history of this system if confirmed by future follow-up observations. With its current orbital configuration, tidal timescales are too long for TOI-4562b to become a hot Jupiter via high eccentricity migration though it is not excluded that interactions with the possible companion could modify TOI4562b's eccentricity and trigger circularization. The characterization of more such young systems is essential to set constraints on models describing giant-planet evolution.
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Hobson, M. J., Jordan, A., Bryant, E. M., Brahm, R., Bayliss, D., Hartman, J. D., et al. (2023). TOI-3235 b: A Transiting Giant Planet around an M4 Dwarf Star. Astrophys. J. Lett., 946(1), L4.
Abstract: We present the discovery of TOI-3235 b, a short-period Jupiter orbiting an M dwarf with a stellar mass close to the critical mass at which stars transition from partially to fully convective. TOI-3235 b was first identified as a candidate from TESS photometry and confirmed with radial velocities from ESPRESSO and ground-based photometry from HATSouth, MEarth-South, TRAPPIST-South, LCOGT, and ExTrA. We find that the planet has a mass of 0.665 +/- 0.025 M-J and a radius of 1.017 +/- 0.044 R-J. It orbits close to its host star, with an orbital period of 2.5926 days but has an equilibrium temperature of approximate to 604 K, well below the expected threshold for radius inflation of hot Jupiters. The host star has a mass of 0.3939 +/- 0.0030 M-circle dot, a radius of 0.3697 +/- 0.0018 R-circle dot;, an effective temperature of 3389 K, and a J-band magnitude of 11.706 +/- 0.025. Current planet formation models do not predict the existence of gas giants such as TOI-3235 b around such low-mass stars. With a high transmission spectroscopy metric, TOI-3235 b is one of the best-suited giants orbiting M dwarfs for atmospheric characterization.
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Hobson, M. J., Trifonov, T., Henning, T., Jordan, A., Rojas, F., Espinoza, N., et al. (2023). Alert Results TOI-199 b: A Well-characterized 100 day Transiting Warm Giant Planet with TTVs Seen from Antarctica 41 of 41 TOI-199 b: A Well-characterized 100 day Transiting Warm Giant Planet with TTVs Seen from Antarctica. Astron. J., 166(5), 201.
Abstract: We present the spectroscopic confirmation and precise mass measurement of the warm giant planet TOI-199 b. This planet was first identified in TESS photometry and confirmed using ground-based photometry from ASTEP in Antarctica including a full 6.5 hr long transit, PEST, Hazelwood, and LCO; space photometry from NEOSSat; and radial velocities (RVs) from FEROS, HARPS, CORALIE, and CHIRON. Orbiting a late G-type star, TOI-199 b has a 104.854-0.002+0.001day period, a mass of 0.17 +/- 0.02 M J, and a radius of 0.810 +/- 0.005 R J. It is the first warm exo-Saturn with a precisely determined mass and radius. The TESS and ASTEP transits show strong transit timing variations (TTVs), pointing to the existence of a second planet in the system. The joint analysis of the RVs and TTVs provides a unique solution for the nontransiting companion TOI-199 c, which has a period of 273.69-0.22+0.26days and an estimated mass of 0.28-0.01+0.02MJ . This period places it within the conservative habitable zone.
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Jenkins, J. S., Diaz, M. R., Kurtovic, N. T., Espinoza, N., Vines, J. I., Rojas, P. A. P., et al. (2020). An ultrahot Neptune in the Neptune desert. Nat. Astron., 4(12), 1148–1157.
Abstract: About 1 out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet(1,2). All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (R-circle plus), or apparently rocky planets smaller than 2 R-circle plus. Such lack of planets of intermediate size (the `hot Neptune desert') has been interpreted as the inability of low-mass planets to retain any hydrogen/ helium (H/He) envelope in the face of strong stellar irradiation. Here we report the discovery of an ultrashort-period planet with a radius of 4.6 R-circle plus and a mass of 29 M-circle plus, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite(3) revealed transits of the bright Sun-like star LTT 9779 every 0.79 days. The planet's mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0(-2.9)(+2.7) % of the total mass. With an equilibrium temperature around 2,000 K, it is unclear how this `ultrahot Neptune' managed to retain such an envelope. Follow-up observations of the planet's atmosphere to better understand its origin and physical nature will be facilitated by the star's brightness (V-mag = 9.8).
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Jordan, A., Brahm, R., Espinoza, N., Henning, T., Jones, M. I., Kossakowski, D., et al. (2020). TOI-677b: A Warm Jupiter (P=11.2 days) on an Eccentric Orbit Transiting a Late F-type Star. Astron. J., 159(4), 10 pp.
Abstract: We report the discovery of TOI-677.b, first identified as a candidate in light curves obtained within Sectors 9 and 10 of the Transiting Exoplanet Survey Satellite (TESS) mission and confirmed with radial velocities. TOI-677.b has a mass of M-p = 1.236(-0.067)(+0.069) M-J, a radius of R-P = 1.170 +/- 0.03 R-J, and orbits its bright host star (V=.9.8 mag) with an orbital period of 11.23660 +/- 0.00011 d, on an eccentric orbit with e = 0.435 +/- 0.024. The host star has a mass of M-star = 1.181 +/- 0.058 M-circle dot, a radius of R. = 1.28(-0.03)(+0.03) R-circle dot, an age of 2.92(-0.73)(+0.80) Gyr and solar metallicity, properties consistent with a main-sequence late-F star with T-eff = 6295 +/- 77 K. We find evidence in the radial velocity measurements of a secondary long-term signal, which could be due to an outer companion. The TOI-677.b system is a well-suited target for Rossiter-Mclaughlin observations that can constrain migration mechanisms of close-in giant planets.
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Lendl, M., Bouchy, F., Gill, S., Nielsen, L. D., Turner, O., Stassun, K., et al. (2020). TOI-222: a single-transit TESS candidate revealed to be a 34-d eclipsing binary with CORALIE, EulerCam, and NGTS. Mon. Not. Roy. Astron. Soc., 492(2), 1761–1769.
Abstract: We report the period, eccentricity, and mass determination for the Transiting Exoplanet Survey Satellite (TESS) single-transit event candidate TOI-222, which displayed a single 3000 ppm transit in the TESS 2-min cadence data from Sector 2. We determine the orbital period via radial velocity measurements (P = 33.9 d), which allowed for ground-based photometric detection of two subsequent transits. Our data show that the companion to TOI-222 is a low-mass star, with a radius of 0.18(-0.10)(+0.39) R-circle dot and a mass of 0.23 +/- 0.01 M-circle dot. This discovery showcases the ability to efficiently discover long-period systems from TESS single-transit events using a combination of radial velocity monitoring coupled with high-precision ground-based photometry.
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Mireles, I., Shporer, A., Grieves, N., Zhou, G., Gunther, M. N., Brahm, R., et al. (2020). TOI 694b and TIC 220568520b: Two Low-mass Companions near the Hydrogen-burning Mass Limit Orbiting Sun-like Stars. Astron. J., 160(3), 13 pp.
Abstract: We report the discovery of TOI 694 b and TIC 220568520 b, two low-mass stellar companions in eccentric orbits around metal-rich Sun-like stars, first detected by the Transiting Exoplanet Survey Satellite (TESS). TOI 694 b has an orbital period of 48.05131 +/- 0.00019 days and eccentricity of 0.51946 +/- 0.00081, and we derive a mass of 89.0 +/- 5.3 M-Jup (0.0849 +/- 0.0051 M-circle dot) and radius of 1.111 +/- 0.017 R-Jup (0.1142 +/- 0.0017 R-circle dot). TIC 220568520 b has an orbital period of 18.55769 +/- 0.00039 days and eccentricity of 0.0964 +/- 0.0032, and we derive a mass of 107.2 +/- 5.2 M-Jup (0.1023 +/- 0.0050 M-circle dot) and radius of 1.248 +/- 0.018 R-Jup (0.1282 +/- 0.0019 R-circle dot). Both binary companions lie close to and above the hydrogen-burning mass threshold that separates brown dwarfs and the lowest-mass stars, with TOI 694 b being 2s above the canonical mass threshold of 0.075 M-circle dot. The relatively long periods of the systems mean that the magnetic fields of the low-mass companions are not expected to inhibit convection and inflate the radius, which according to one leading theory is common in similar objects residing in short-period tidally synchronized binary systems. Indeed we do not find radius inflation for these two objects when compared to theoretical isochrones. These two new objects add to the short but growing list of low-mass stars with well-measured masses and radii, and highlight the potential of the TESS mission for detecting such rare objects orbiting bright stars.
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Nielsen, L. D., Brahm, R., Bouchy, F., Espinoza, N., Turner, O., Rappaport, S., et al. (2020). Three short-period Jupiters from TESS: HIP 65Ab, TOI-157b, and TOI-169b. Astron. Astrophys., 639, 17 pp.
Abstract: We report the confirmation and mass determination of three hot Jupiters discovered by the Transiting Exoplanet Survey Satellite (TESS) mission: HIP 65Ab (TOI-129, TIC-201248411) is an ultra-short-period Jupiter orbiting a bright (V = 11.1 mag) K4-dwarf every 0.98 days. It is a massive 3.213 +/- 0.078 M-J planet in a grazing transit configuration with an impact parameter of b = 1.17(-0.08)(+0.10) b=1.17-0.08+0.10 . As a result the radius is poorly constrained, 2.03(-0.49)(+0.61)R(J) 2.03-0.49+0.61 RJ . The planet's distance to its host star is less than twice the separation at which it would be destroyed by Roche lobe overflow. It is expected to spiral into HIP 65A on a timescale ranging from 80 Myr to a few gigayears, assuming a reduced tidal dissipation quality factor of Q(s)(') = 10(7) – 10(9) Qs ' =107-109 . We performed a full phase-curve analysis of the TESS data and detected both illumination- and ellipsoidal variations as well as Doppler boosting. HIP 65A is part of a binary stellar system, with HIP 65B separated by 269 AU (3.95 arcsec on sky). TOI-157b (TIC 140691463) is a typical hot Jupiter with a mass of 1.18 +/- 0.13 M-J and a radius of 1.29 +/- 0.02 R-J. It has a period of 2.08 days, which corresponds to a separation of just 0.03 AU. This makes TOI-157 an interesting system, as the host star is an evolved G9 sub-giant star (V = 12.7). TOI-169b (TIC 183120439) is a bloated Jupiter orbiting a V = 12.4 G-type star. It has a mass of 0.79 +/- 0.06 M-J and a radius of 1.09(-0.05)(+0.08)R(J) 1.09-0.05+0.08<mml:msub>RJ . Despite having the longest orbital period (P = 2.26 days) of the three planets, TOI-169b receives the most irradiation and is situated on the edge of the Neptune desert. All three host stars are metal rich with [Fe / H] ranging from 0.18 to0.24.
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Osborn, A., Armstrong, D. J., Cale, B., Brahm, R., Wittenmyer, R. A., Dai, F., et al. (2021). TOI-431/HIP 26013: a super-Earth and a sub-Neptune transiting a bright, early K dwarf, with a third RV planet. Mon. Not. Roy. Astron. Soc., 507(2), 2782–2803.
Abstract: We present the bright (V-mag = 9.12), multiplanet system TOI-431, characterized with photometry and radial velocities (RVs). We estimate the stellar rotation period to be 30.5 +/- 0.7 d using archival photometry and RVs. Transiting Exoplanet Survey Satellite (TESS) objects of Interest (TOI)-431b is a super-Earth with a period of 0.49 d, a radius of 1.28 +/- 0.04 R-circle plus, a mass of 3.07 +/- 0.35 M-circle plus, and a density of 8.0 +/- 1.0 g cm(-3); TOI-431 d is a sub-Neptune with a period of 12.46 d, a radius of 3.29 +/- 0.09 R-circle plus, a mass of M-circle plus, and a density of 1.36 +/- 0.25 g cm(-3). We find a third planet, TOI-431c, in the High Accuracy Radial velocity Planet Searcher RV data, but it is not seen to transit in the TESS light curves. It has an Msin i of M-circle plus, and a period of 4.85 d. TOI-431d likely has an extended atmosphere and is one of the most well-suited TESS discoveries for atmospheric characterization, while the super-Earth TOI-431b may be a stripped core. These planets straddle the radius gap, presenting an interesting case-study for atmospheric evolution, and TOI-431b is a prime TESS discovery for the study of rocky planet phase curves.
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