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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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Espinoza, N., Brahm, R., Henning, T., Jordan, A., Dorn, C., Rojas, F., et al. (2020). HD 213885b: a transiting 1-d-period super-Earth with an Earth-like composition around a bright (V=7.9) star unveiled by TESS. Mon. Not. Roy. Astron. Soc., 491(2), 2982–2999.
Abstract: We report the discovery of the 1.008-d, ultrashort period (USP) super-EarthHD213885b (TOI141b) orbiting the bright (V= 7.9) star HD 213885 (TOI-141, TIC 403224672), detected using photometry from the recently launched TESS mission. Using FEROS, HARPS, and CORALIE radial velocities, we measure a precise mass of 8.8 +/- 0.6M. for this 1.74 +/- 0.05 R. exoplanet, which provides enough information to constrain its bulk composition – similar to Earth's but enriched in iron. The radius, mass, and stellar irradiation of HD 213885b are, given our data, very similar to 55 Cancri e, making this exoplanet a good target to perform comparative exoplanetology of short period, highly irradiated super-Earths. Our precise radial velocities reveal an additional 4.78-d signal which we interpret as arising from a second, non-transiting planet in the system, HD 213885c, whoseminimum mass of 19.9 +/- 1.4M. makes it consistent with being a Neptune-mass exoplanet. The HD 213885 system is very interesting from the perspective of future atmospheric characterization, being the second brightest star to host an USP transiting super-Earth (with the brightest star being, in fact, 55 Cancri). Prospects for characterization with present and future observatories are discussed.
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Jones, M. I., Reinarz, Y., Brahm, R.., Tala Pinto, M., Eberhardt, J., Rojas, F., et al. (2024). A long-period transiting substellar companion in the super-Jupiters to brown dwarfs mass regime and a prototypical warm-Jupiter detected by TESS. Astron. Astrophys., 683, A192.
Abstract: We report on the confirmation and follow-up characterization of two long-period transiting substellar companions on low-eccentricity orbits around TIC 4672985 and TOI-2529, whose transit events were detected by the TESS space mission. Ground-based photometric and spectroscopic follow-up from different facilities, confirmed the substellar nature of TIC 4672985 b, a massive gas giant in the transition between the super-Jupiters and brown dwarfs mass regime. From the joint analysis we derived the following orbital parameters: P = 69.0480(-0.0005)(+0.0004) d, M-p = 12.74(-1.01)(+1.01) M-J, R-p = 1.026(-0.067)(+0.065) R-J and e = 0.018(-0.004)(+0.004). In addition, the RV time series revealed a significant trend at the similar to 350 m s(-1) yr(-1) level, which is indicative of the presence of a massive outer companion in the system. TIC 4672985 b is a unique example of a transiting substellar companion with a mass above the deuterium-burning limit, located beyond 0.1 AU and in a nearly circular orbit. These planetary properties are difficult to reproduce from canonical planet formation and evolution models. For TOI-2529 b, we obtained the following orbital parameters: P = 64.5949(-0.0003)(+0.0003) d, M-p = 2.340(-0.195)(+0.197) M-J, R-p = 1.030(-0.050)(+0.050) R-J and e = 0.021(-0.015)(+0.024), making this object a new example of a growing population of transiting warm giant planets.
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Leleu, A., Alibert, Y., Hara, N. C., Hooton, M. J., Wilson, T. G., Robutel, P., et al. (2021). Six transiting planets and a chain of Laplace resonances in TOI-178. Astron. Astrophys., 649, A26.
Abstract: Determining the architecture of multi-planetary systems is one of the cornerstones of understanding planet formation and evolution. Resonant systems are especially important as the fragility of their orbital configuration ensures that no significant scattering or collisional event has taken place since the earliest formation phase when the parent protoplanetary disc was still present. In this context, TOI-178 has been the subject of particular attention since the first TESS observations hinted at the possible presence of a near 2:3:3 resonant chain. Here we report the results of observations from CHEOPS, ESPRESSO, NGTS, and SPECULOOS with the aim of deciphering the peculiar orbital architecture of the system. We show that TOI-178 harbours at least six planets in the super-Earth to mini-Neptune regimes, with radii ranging from
1.152(-0.070)(+0.073)</textual-form> 1.152-0.070+0.073 to 2.87(-0.13)(+0.14)</textual-form> 2.87-0.13+0.14 Earth radii and periods of 1.91, 3.24, 6.56, 9.96, 15.23, and 20.71 days. All planets but the innermost one form a 2:4:6:9:12 chain of Laplace resonances, and the planetary densities show important variations from planet to planet, jumping from 1.02(-0.23)(+0.28)</textual-form> 1.02-0.23+0.28 to 0.177(-0.061)(+0.055)</textual-form> 0.177-0.061+0.055 times the Earth's density between planets c and d. Using Bayesian interior structure retrieval models, we show that the amount of gas in the planets does not vary in a monotonous way, contrary to what one would expect from simple formation and evolution models and unlike other known systems in a chain of Laplace resonances. The brightness of TOI-178 (H = 8.76 mag, J = 9.37 mag, V = 11.95 mag) allows for a precise characterisation of its orbital architecture as well as of the physical nature of the six presently known transiting planets it harbours. The peculiar orbital configuration and the diversity in average density among the planets in the system will enable the study of interior planetary structures and atmospheric evolution, providing important clues on the formation of super-Earths and mini-Neptunes. Keywords: HOT SUPER-EARTHS; TESS INPUT CATALOG; RADIUS DISTRIBUTION; MASS; SYSTEM; MODEL; STARS; MIGRATION; DYNAMICS; TOOL
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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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Psaridi, A., Bouchy, F., Lendl, M., Akinsanmi, B., Stassun, K. G., Smalley, B., et al. (2023). Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS TOI-615b, TOI-622b, and TOI-2641b. Astron. Astrophys., 675, A39.
Abstract: While the sample of confirmed exoplanets continues to grow, the population of transiting exoplanets around early-type stars is still limited. These planets allow us to investigate the planet properties and formation pathways over a wide range of stellar masses and study the impact of high irradiation on hot Jupiters orbiting such stars. We report the discovery of TOI-615b, TOI-622b, and TOI-2641b, three Saturn-mass planets transiting main sequence, F-type stars. The planets were identified by the Transiting Exoplanet Survey Satellite (TESS) and confirmed with complementary ground-based and radial velocity observations. TOI-615b is a highly irradiated (similar to 1277 F-circle dot) and bloated Saturn-mass planet (1.69(-0.06)(+0.05) R-Jup and 0.43(-0.08)(+0.09) M-Jup) in a 4.66 day orbit transiting a 6850 K star. TOI-622b has a radius of 0.82(-0.03)(+0.03) R-Jup and a mass of 0.30(-0.08)(+0.07) M-Jup in a 6.40 day orbit. Despite its high insolation flux (similar to 600 F-circle dot), TOI-622b does not show any evidence of radius inflation. TOI-2641b is a 0.39(-0.04)(+0.02) M-Jup planet in a 4.88 day orbit with a grazing transit (b = 1.04(-0.06)(+0.05)) that results in a poorly constrained radius of 1.61(-0.64)(+0.46) R-Jup. Additionally, TOI-615b is considered attractive for atmospheric studies via transmission spectroscopy with ground-based spectrographs and JWST. Future atmospheric and spin-orbit alignment observations are essential since they can provide information on the atmospheric composition, formation, and migration of exoplanets across various stellar types.
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Sedaghati, E., MacDonald, R. J., Casasayas-Barris, N., Hoeijmakers, H. J., Boffin, H. M. J., Rodler, F., et al. (2021). A spectral survey of WASP-19b with ESPRESSO. Mon. Not. Roy. Astron. Soc., 505(1), 435–458.
Abstract: High-resolution precision spectroscopy provides a multitude of robust techniques for probing exoplanetary atmospheres. We present multiple VLT/ESPRESSO transit observations of the hot-Jupiter exoplanet WASP-19b with previously published but disputed atmospheric features from low resolution studies. Through spectral synthesis and modelling of the Rossiter-McLaughlin (RM) effect we calculate stellar, orbital and physical parameters for the system. From narrow-band spectroscopy we do not detect any of Hi, Fei, Mgi, Cai, Nai, and Ki neutral species, placing upper limits on their line contrasts. Through cross-correlation analyses with atmospheric models, we do not detect Fei and place a 3 sigma upper limit of on its mass fraction, from injection and retrieval. We show the inability to detect the presence of H2O for known abundances, owing to lack of strong absorption bands, as well as relatively low S/N ratio. We detect a barely significant peak (3.02 +/- 0.15 sigma) in the cross-correlation map for TiO, consistent with the sub-solar abundance previously reported. This is merely a hint for the presence of TiO and does not constitute a confirmation. However, we do confirm the presence of previously observed enhanced scattering towards blue wavelengths, through chromatic RM measurements, pointing to a hazy atmosphere. We finally present a reanalysis of low-resolution transmission spectra of this exoplanet, concluding that unocculted starspots alone cannot explain previously detected features. Our reanalysis of the FORS2 spectra of WASP-19b finds a similar to 100x sub-solar TiO abundance, precisely constrained to , consistent with the TiO hint from ESPRESSO. We present plausible paths to reconciliation with other seemingly contradicting results.
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