| 1. |
- Fukui, A., et al.
(författare)
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TOI-1749: an M dwarf with a Trio of Planets including a Near-resonant Pair
- 2021
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 162:4
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of one super-Earth- (TOI-1749b) and two sub-Neptune-sized planets (TOI-1749c and TOI-1749d) transiting an early M dwarf at a distance of 100 pc, which were first identified as planetary candidates using data from the TESS photometric survey. We have followed up this system from the ground by means of multiband transit photometry, adaptive optics imaging, and low-resolution spectroscopy, from which we have validated the planetary nature of the candidates. We find that TOI-1749b, c, and d have orbital periods of 2.39, 4.49, and 9.05 days, and radii of 1.4, 2.1, and 2.5 R (circle plus), respectively. We also place 95% confidence upper limits on the masses of 57, 14, and 15 M (circle plus) for TOI-1749b, c, and d, respectively, from transit timing variations. The periods, sizes, and tentative masses of these planets are in line with a scenario in which all three planets initially had a hydrogen envelope on top of a rocky core, and only the envelope of the innermost planet has been stripped away by photoevaporation and/or core-powered mass-loss mechanisms. These planets are similar to other planetary trios found around M dwarfs, such as TOI-175b,c,d and TOI-270b,c,d, in the sense that the outer pair has a period ratio within 1% of 2. Such a characteristic orbital configuration, in which an additional planet is located interior to a near 2:1 period-ratio pair, is relatively rare around FGK dwarfs.
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| 2. |
- Barragan, O., et al.
(författare)
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The young HD 73583 (TOI-560) planetary system: two 10-M-circle plus mini-Neptunes transiting a 500-Myr-old, bright, and active K dwarf
- 2022
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 514:2, s. 1606-1627
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Tidskriftsartikel (refereegranskat)abstract
- We present the discovery and characterization of two transiting planets observed by TESS in the light curves of the young and bright (V = 9.67) star HD73583 (TOI-560). We perform an intensive spectroscopic and photometric space- and ground-based follow-up in order to confirm and characterize the system. We found that HD73583 is a young (similar to 500 Myr) active star with a rotational period of 12.08 +/- 0.11 d, and a mass and radius of 0.73 +/- 0.02 M-circle dot and 0.65 +/- 0.02 R-circle dot, respectively. HD 73583 b (P-b = 6.3980420(-0.0000062)(+0.0000067 )d) has a mass and radius of 10.2(-3.1)(+3.4) M-circle plus and 2.79 +/- 0.10 R-circle plus, respectively, which gives a density of 2.58(-0.81)(+0.95) g cm(-3). HD 73583 c (P-c = 18.87974(-0.00074)(+0.00086) d) has a mass and radius of 9.7(-1.7)(+1.8) M-circle plus and 2.39(-0.09)(+0.10) R-circle plus, respectively, which translates to a density of 3.88(-0.80)(+0.91) g cm(-3). Both planets are consistent with worlds made of a solid core surrounded by a volatile envelope. Because of their youth and host star brightness, they both are excellent candidates to perform transmission spectroscopy studies. We expect ongoing atmospheric mass-loss for both planets caused by stellar irradiation. We estimate that the detection of evaporating signatures on H and He would be challenging, but doable with present and future instruments.
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| 3. |
- Esparza-Borges, E., et al.
(författare)
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A hot sub-Neptune in the desert and a temperate super-Earth around faint M dwarfs Color validation of TOI-4479b and TOI-2081b
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We report the discovery and validation of two TESS exoplanets orbiting faint M dwarfs: TOI-4479b and TOI-2081b. Methods. We jointly analyzed space (TESS mission) and ground-based (MuSCAT2, MuSCAT3 and SINISTRO instruments) light curves using our multicolor photometry transit analysis pipeline. This allowed us to compute contamination limits for both candidates and validate them as planet-sized companions. Results. We found TOI-4479b to be a sub-Neptune-sized planet (R-p = 2.82(-0.63)(+0.65) R-circle plus) and TOI-2081b to be a super-Earth-sized planet (R-p = 2.04(-0.54)(+0.50) R-circle plus). Furthermore, we obtained that TOI-4479b, with a short orbital period of 1.15890(-0.00001)(+0.00002) days, lies within the Neptune desert and is in fact the largest nearly ultra-short period planet around an M dwarf known to date. Conclusions. These results make TOI-4479b rare among the currently known exoplanet population of M dwarf stars and an especially interesting target for spectroscopic follow-up and future studies of planet formation and evolution.
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| 4. |
- Kawauchi, K., et al.
(författare)
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Validation and atmospheric exploration of the sub-Neptune TOI-2136b around a nearby M3 dwarf
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
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Tidskriftsartikel (refereegranskat)abstract
- Context. The NASA space telescope TESS is currently in the extended mission of its all-sky search for new transiting planets. Of the thousands of candidates that TESS is expected to deliver, transiting planets orbiting nearby M dwarfs are particularly interesting targets since they provide a great opportunity to characterize their atmospheres by transmission spectroscopy. Aims. We aim to validate and characterize the new sub-Neptune-sized planet candidate TOI-2136.01 orbiting a nearby M dwarf (d = 33.36 +/- 0.02 pc, T-eff = 3373 +/- 108 K) with an orbital period of 7.852 days. Methods. We use TESS data, ground-based multicolor photometry, and radial velocity measurements with the InfraRed Doppler (IRD) instrument on the Subaru Telescope to validate the planetary nature of TOI-2136.01, and estimate the stellar and planetary parameters. We also conduct high-resolution transmission spectroscopy to search for helium in its atmosphere. Results. We confirm that TOI-2136.01 (now named TOI-2136b) is a bona fide planet with a planetary radius of R-p = 2.20 +/- 0.07 R-circle plus and a mass of M-p = 4.7(-2.6)(+3.1) M-circle plus. We also search for helium 10830 angstrom absorption lines and place an upper limit on the equivalent width of <7.8 m angstrom and on the absorption signal of <1.44% with 95% confidence. Conclusions. TOI-2136b is a sub-Neptune transiting a nearby and bright star (J = 10.8 mag), and is a potentially hycean planet, which is a new class of habitable planets with large oceans under a H-2-rich atmosphere, making it an excellent target for atmospheric studies to understand the formation, evolution, and habitability of the small planets.
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| 5. |
- Parviainen, H., et al.
(författare)
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TOI-2266 b: A keystone super-Earth at the edge of the M dwarf radius valley
- 2024
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 683
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Tidskriftsartikel (refereegranskat)abstract
- We validate the Transiting Exoplanet Survey Satellite (TESS) object of interest TOI-2266.01 (TIC 8348911) as a small transiting planet (most likely a super-Earth) orbiting a faint M5 dwarf (V = 16.54) on a 2.33 d orbit. The validation is based on an approach where multicolour transit light curves are used to robustly estimate the upper limit of the transiting object's radius. Our analysis uses SPOC-pipeline TESS light curves from Sectors 24, 25, 51, and 52, simultaneous multicolour transit photometry observed with MuSCAT2, MuSCAT3' and HiPERCAM, and additional transit photometry observed with the LCOGT telescopes. TOI-2266 b is found to be a planet with a radius of 1.54 ± 0.09 R, which locates it at the edge of the transition zone between rocky planets, water-rich planets, and sub-Neptunes (the so-called M dwarf radius valley). The planet is amenable to ground-based radial velocity mass measurement with red-sensitive spectrographs installed in large telescopes, such as MAROON-X and Keck Planet Finder (KPF), which makes it a valuable addition to a relatively small population of planets that can be used to probe the physics of the transition zone. Further, the planet's orbital period of 2.33 days places it inside a 'keystone planet'wedge in the period-radius plane where competing planet formation scenarios make conflicting predictions on how the radius valley depends on the orbital period. This makes the planet also a welcome addition to the small population of planets that can be used to test small-planet formation scenarios around M dwarfs.
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| 6. |
- Hawthorn, F., et al.
(författare)
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TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 520:3, s. 3649-3668
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Tidskriftsartikel (refereegranskat)abstract
- We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and Sector 38. TOI-836 is a bright (T = 8.5 mag), high proper motion (∼200 mas yr−1), low metallicity ([Fe/H]≈−0.28) K-dwarf with a mass of 0.68 ± 0.05 M and a radius of 0.67 ± 0.01 R. We obtain photometric follow-up observations with a variety of facilities, and we use these data sets to determine that the inner planet, TOI-836 b, is a 1.70 ± 0.07 R super-Earth in a 3.82-d orbit, placing it directly within the so-called ‘radius valley’. The outer planet, TOI-836 c, is a 2.59 ± 0.09 R mini-Neptune in an 8.60-d orbit. Radial velocity measurements reveal that TOI-836 b has a mass of 4.5 ± 0.9 M, while TOI-836 c has a mass of 9.6 ± 2.6 M. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 min for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet.
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| 7. |
- Bell, Taylor, et al.
(författare)
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Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b
- 2024
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Ingår i: Nature Astronomy. - 2397-3366. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Hot Jupiters are among the best-studied exoplanets, but it is still poorly understood how their chemical composition and cloud properties vary with longitude. Theoretical models predict that clouds may condense on the nightside and that molecular abundances can be driven out of equilibrium by zonal winds. Here we report a phase-resolved emission spectrum of the hot Jupiter WASP-43b measured from 5 μm to 12 μm with the JWST’s Mid-Infrared Instrument. The spectra reveal a large day–night temperature contrast (with average brightness temperatures of 1,524 ± 35 K and 863 ± 23 K, respectively) and evidence for water absorption at all orbital phases. Comparisons with three-dimensional atmospheric models show that both the phase-curve shape and emission spectra strongly suggest the presence of nightside clouds that become optically thick to thermal emission at pressures greater than ~100 mbar. The dayside is consistent with a cloudless atmosphere above the mid-infrared photosphere. Contrary to expectations from equilibrium chemistry but consistent with disequilibrium kinetics models, methane is not detected on the nightside (2σ upper limit of 1–6 ppm, depending on model assumptions). Our results provide strong evidence that the atmosphere of WASP-43b is shaped by disequilibrium processes and provide new insights into the properties of the planet’s nightside clouds. However, the remaining discrepancies between our observations and our predictive atmospheric models emphasize the importance of further exploring the effects of clouds and disequilibrium chemistry in numerical models.
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| 8. |
- Fukui, Akihiko, et al.
(författare)
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TOI-2285b: A 1.7 Earth-radius planet near the habitable zone around a nearby M dwarf
- 2022
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Ingår i: Publication of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 2053-051X .- 0004-6264. ; 74:1, s. L1-L8
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of TO1-2285b, a sub-Neptune-sized planet transiting a nearby (42 pc) M dwarf with a period of 27.3 d. We identified the transit signal from the Transiting Exoplanet Survey Satellite photometric data, which we confirmed with ground-based photometric observations using the multiband imagers MuSCAT2 and MuSCAT3. Combining these data with other follow-up observations including high-resolution spectroscopy with the Tillinghast Reflector Echelle Spectrograph, high-resolution imaging with the SPeckle Polarimeter, and radial velocity (RV) measurements with the InfraRed Doppler instrument, we find that the planet has a radius of 1.74 +/- 0.08 R-circle plus, a mass of <19.5 M-circle plus + (95% c.I.), and an insolation flux of 1.54 +/- 0.14 times that of the Earth. Although the planet resides just outside the habitable zone for a rocky planet, if the planet harbors an H2O layer under a hydrogen-rich atmosphere, then liquid water could exist on the surface of the H2O layer depending on the planetary mass and water mass fraction. The bright host star in the near-infrared (K-s = 9.0) makes this planet an excellent target for further RV and atmospheric observations to improve our understanding of the composition, formation, and habitability of sub-Neptune-sized planets.
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| 9. |
- Hobson, Melissa J., et al.
(författare)
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TOI-199 b : A Well-characterized 100 day Transiting Warm Giant Planet with TTVs Seen from Antarctica
- 2023
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Ingår i: Astronomical Journal. - 0004-6256. ; 166:5
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Tidskriftsartikel (refereegranskat)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 + 0.001 day 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 + 0.26 days and an estimated mass of 0.28 − 0.01 + 0.02 M J . This period places it within the conservative habitable zone.
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| 10. |
- Morello, Giuseppe, 1989, et al.
(författare)
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TOI-1442 b and TOI-2445 b: Two potentially rocky ultra-short period planets around M dwarfs
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 673
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Tidskriftsartikel (refereegranskat)abstract
- Context. Exoplanets with orbital periods of less than one day are known as ultra-short period (USP) planets. They are relatively rare products of planetary formation and evolution processes, but especially favourable for characterisation with current planet detection methods. At the time of writing, 125 USP planets have already been confirmed. Aims. Our aim is to validate the planetary nature of two new transiting planet candidates around M dwarfs announced by the NASA Transiting Exoplanet Survey Satellite (TESS), registered as TESS Objects of Interest (TOIs) TOI-1442.01 and TOI-2445.01. Methods. We used TESS data, ground-based photometric light curves, and Subaru/IRD spectrograph radial velocity (RV) measurements to validate both planetary candidates and to establish their physical properties. Results. TOI-1442 b is a validated exoplanet with an orbital period of P = 0.4090682 ± 0.0000004 day, a radius of Rp = 1.15 ± 0.06 R☉, and equilibrium temperature of Tp,eq = 1357+−4942 K. TOI-2445 b is also validated with an orbital period of P = 0.3711286 ± 0.0000004 day, a radius of Rp = 1.33 ± 0.09 R☉, and equilibrium temperature of Tp,eq = 1330+−6156 K. Their physical properties align with current empirical trends and formation theories of USP planets. Based on the RV measurements, we set 3σ upper mass limits of 8 M☉ and 20 M☉, thus confirming the non-stellar, sub-Jovian nature of both transiting objects. More RV measurements will be needed to constrain the planetary masses and mean densities, and the predicted presence of outer planetary companions. These targets extend the small sample of USP planets orbiting around M dwarfs up to 21 members. They are also among the 20 most suitable terrestrial planets for atmospheric characterisation via secondary eclipse with the James Webb Space Telescope, according to a widespread emission spectroscopy metric.
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