| 1. |
- Tuson, A., et al.
(författare)
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TESS and CHEOPS discover two warm sub-Neptunes transiting the bright K-dwarf HD 15906
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 523:2, s. 3090-3118
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of two warm sub-Neptunes transiting the bright (G = 9.5 mag) K-dwarf HD 15906 (TOI 461, TIC 4646810). This star was observed by the Transiting Exoplanet Survey Satellite (TESS) in sectors 4 and 31, revealing two small transiting planets. The inner planet, HD 15906 b, was detected with an unambiguous period but the outer planet, HD 15906 c, showed only two transits separated by ∼ 734 d, leading to 36 possible values of its period. We performed follow-up observations with the CHaracterising ExOPlanet Satellite (CHEOPS) to confirm the true period of HD 15906 c and improve the radius precision of the two planets. From TESS, CHEOPS, and additional ground-based photometry, we find that HD 15906 b has a radius of 2.24 ± 0.08 R and a period of 10.924709 ± 0.000032 d, whilst HD 15906 c has a radius of 2.93+−000607 R and a period of 21.583298+−00000055000052 d. Assuming zero bond albedo and full day-night heat redistribution, the inner and outer planet have equilibrium temperatures of 668 ± 13 K and 532 ± 10 K, respectively. The HD 15906 system has become one of only six multiplanet systems with two warm (700 K) sub-Neptune sized planets transiting a bright star (G ≤ 10 mag). It is an excellent target for detailed characterization studies to constrain the composition of sub-Neptune planets and test theories of planet formation and evolution.
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| 2. |
- Carleo, Ilaria, et al.
(författare)
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The Multiplanet System TOI-421*
- 2020
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 160:3
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Crossfield, Ian J. M., et al.
(författare)
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197 CANDIDATES AND 104 VALIDATED PLANETS IN K2's FIRST FIVE FIELDS
- 2016
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 226:1
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Tidskriftsartikel (refereegranskat)abstract
- We present 197 planet candidates discovered using data from the first year of the NASA K2 mission (Campaigns 0-4), along with the results of an intensive program of photometric analyses, stellar spectroscopy, high-resolution imaging, and statistical validation. We distill these candidates into sets of 104 validated planets (57 in multi-planet systems), 30 false positives, and 63 remaining candidates. Our validated systems span a range of properties, with median values of R-P = 2.3 R-circle plus, P = 8.6 days, T-eff = 5300 K, and Kp = 12.7 mag. Stellar spectroscopy provides precise stellar and planetary parameters for most of these systems. We show that K2 has increased by 30% the number of small planets known to orbit moderately bright stars (1-4 R-circle plus, Kp = 9-13. mag). Of particular interest are 76 planets smaller than 2 R-circle plus, 15 orbiting stars brighter than Kp = 11.5. mag, 5 receiving Earth-like irradiation levels, and several multi-planet systems-including 4 planets orbiting the M dwarf K2-72 near mean-motion resonances. By quantifying the likelihood that each candidate is a planet we demonstrate that our candidate sample has an overall false positive rate of 15%-30%, with rates substantially lower for small candidates (<2 R-circle plus) and larger for candidates with radii >8 R-circle plus and/or with P < 3 days. Extrapolation of the current planetary yield suggests that K2 will discover between 500 and 1000 planets in its planned four-year mission, assuming sufficient follow-up resources are available. Efficient observing and analysis, together with an organized and coherent follow-up strategy, are essential for maximizing the efficacy of planet-validation efforts for K2, TESS, and future large-scale surveys.
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| 4. |
- de Leon, J. P., et al.
(författare)
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37 new validated planets in overlapping K2 campaigns
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 508:1, s. 195-218
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Tidskriftsartikel (refereegranskat)abstract
- We analysed 68 candidate planetary systems first identified during Campaigns 5 and 6 (C5 and C6) of the NASA K2 mission. We set out to validate these systems by using a suite of follow-up observations, including adaptive optics, speckle imaging, and reconnaissance spectroscopy. The overlap between C5 with C16 and C18, and C6 with C17, yields light curves with long baselines that allow us to measure the transit ephemeris very precisely, revisit single transit candidates identified in earlier campaigns, and search for additional transiting planets with longer periods not detectable in previous works. Using vespa, we compute false positive probabilities of less than 1 percent for 37 candidates orbiting 29 unique host stars and hence statistically validate them as planets. These planets have a typical size of 2.2 R-circle plus and orbital periods between 1.99 and 52.71 d. We highlight interesting systems including a sub-Neptune with the longest period detected by K2, sub-Saturns around F stars, several multiplanetary systems in a variety of architectures. These results show that a wealth of planetary systems still remains in the K2 data, some of which can be validated using minimal follow-up observations and taking advantage of analyses presented in previous catalogues.
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| 5. |
- 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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| 6. |
- Subjak, Jan, et al.
(författare)
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TOI-503: The First Known Brown-dwarf Am-star Binary from the TESS Mission
- 2020
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 1538-3881 .- 0004-6256. ; 159:4
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of an intermediate-mass transiting brown dwarf (BD), TOI-503b, from the TESS mission. TOI-503b is the first BD discovered by TESS, and it has circular orbit around a metallic-line A-type star with a period of P.=.3.6772.+/-.0.0001 days. The light curve from TESS indicates that TOI-503b transits its host star in a grazing manner, which limits the precision with which we measure the BD's radius ( = R 1.34+ R b 0.150.26 J). We obtained highresolution spectroscopic observations with the FIES, Ondr.ejov, PARAS, Tautenburg, and TRES spectrographs, and measured the mass of TOI-503b to be Mb.=.53.7.+/-.1.2 MJ. The host star has a mass of Ma.=.1.80.+/-.0.06Me, a radius of Ra.=.1.70.+/-.0.05Re, an effective temperature of Teff.=.7650.+/-.160 K, and a relatively high metallicity of 0.61.+/-.0.07 dex. We used stellar isochrones to derive the age of the system to be 180 Myr, which places its age between that of RIK 72b (a 10 Myr old BD in the Upper Scorpius stellar association) and AD 3116b (a 600 Myr old BD in the Praesepe cluster). Given the difficulty in measuring the tidal interactions between BDs and their host stars, we cannot precisely say whether this BD formed in situ or has had its orbit circularized by its host star over the relatively short age of the system. Instead, we offer an examination of plausible values for the tidal quality factor for the star and BD. TOI-503b joins a growing number of known short-period, intermediate-mass BDs orbiting mainsequence stars, and is the second such BD known to transit an A star, after HATS-70b. With the growth in the population in this regime, the driest region in the BD desert (35-55MJ sin i) is reforesting.
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