60 research outputs found
TOI-3235 b: A Transiting Giant Planet around an M4 Dwarf Star
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 â 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 â, a radius of 0.3697 ± 0.0018 R â, 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
TOI-4336 A b:A temperate sub-Neptune ripe for atmospheric characterization in a nearby triple M-dwarf system
Small planets transiting bright nearby stars are essential to our understanding of the formation and evolution of exoplanetary systems. However, few constitute prime targets for atmospheric characterization, and even fewer are part of multiple star systems. This work aims to validate TOI-4336 A b, a sub-Neptune-sized exoplanet candidate identified by the TESS space-based transit survey around a nearby M-dwarf. We validate the planetary nature of TOI-4336 A b through the global analysis of TESS and follow-up multi-band high-precision photometric data from ground-based telescopes, medium- and high-resolution spectroscopy of the host star, high-resolution speckle imaging, and archival images. The newly discovered exoplanet TOI-4336 A b has a radius of 2.1±0.1Râ. Its host star is an M3.5-dwarf star of mass 0.33±0.01Mâ and radius 0.33±0.02Râ member of a hierarchical triple M-dwarf system 22 pc away from the Sun. The planet's orbital period of 16.3 days places it at the inner edge of the Habitable Zone of its host star, the brightest of the inner binary pair. The parameters of the system make TOI-4336 A b an extremely promising target for the detailed atmospheric characterization of a temperate sub-Neptune by transit transmission spectroscopy with JWST
TOI-3235 b: a transiting giant planet around an M4 dwarf star
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
and a radius of . It
orbits close to its host star, with an orbital period of ,
but has an equilibrium temperature of , well below
the expected threshold for radius inflation of hot Jupiters. The host star has
a mass of , a radius of
, an effective temperature of , and a J-band magnitude of . 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.Comment: 15 pages, 4 figures. Accepted for publication in APJ
TOI-2084 b and TOI-4184 b: two new sub-Neptunes around M dwarf stars
We present the discovery and validation of two TESS exoplanets orbiting
nearby M dwarfs: TOI-2084b, and TOI-4184b. We characterized the host stars by
combining spectra from Shane/Kast and Magellan/FIRE, SED (Spectral Energy
Distribution) analysis, and stellar evolutionary models. In addition, we used
Gemini-South/Zorro & -North/Alopeke high-resolution imaging, archival science
images, and statistical validation packages to support the planetary
interpretation. We performed a global analysis of multi-colour photometric data
from TESS and ground-based facilities in order to derive the stellar and
planetary physical parameters for each system. We find that TOI-2084b and
TOI-4184b are sub-Neptune-sized planets with radii of Rp = 2.47 +/- 0.13R_Earth
and Rp = 2.43 +/- 0.21R_Earth, respectively. TOI-2084b completes an orbit
around its host star every 6.08 days, has an equilibrium temperature of T_eq =
527 +/- 8K and an irradiation of S_p = 12.8 +/- 0.8 S_Earth. Its host star is a
dwarf of spectral M2.0 +/- 0.5 at a distance of 114pc with an effective
temperature of T_eff = 3550 +/- 50 K, and has a wide, co-moving M8 companion at
a projected separation of 1400 au. TOI-4184b orbits around an M5.0 +/- 0.5 type
dwarf star (Kmag = 11.87) each 4.9 days, and has an equilibrium temperature of
T_eq = 412 +/- 8 K and an irradiation of S_p = 4.8 +/- 0.4 S_Earth. TOI-4184 is
a metal poor star ([Fe/H] = -0.27 +/- 0.09 dex) at a distance of 69 pc with an
effective temperature of T_eff = 3225 +/- 75 K. Both planets are located at the
edge of the sub-Jovian desert in the radius-period plane. The combination of
the small size and the large infrared brightness of their host stars make these
new planets promising targets for future atmospheric exploration with JWST.Comment: Accepted for publication in A&
TOI-2084 b and TOI-4184 b:two new sub-Neptunes around M dwarf stars
Funding: The research leading to these results has received funding from the ARC grant for Concerted Research Actions, financed by the Wallonia-Brussels Federation. This research is in part funded by the European Unionâs Horizon 2020 research and innovation program (grants agreements n⊠803193/BEBOP), and from the Science and Technology Facilities Council (STFC; grant n⊠ST/S00193X/1). U.G.J. gratefully acknowledges support from tthe European Union H2020-MSCA-ITN-2019 under grant No. 860470 (CHAMELEON). We acknowledge funding from the European Research Council under the ERC Grant Agreement n. 337591-ExTrA.We present the discovery and validation of two TESS exoplanets orbiting nearby M dwarfs: TOI-2084 b, and TOI-4184b. We characterized the host stars by combining spectra from Shane/Kast and Magellan/FIRE, spectral energy distribution analysis, and stellar evolutionary models. In addition, we used Gemini-South/Zorro & -North/Alopeke high-resolution imaging, archival science images, and statistical validation packages to support the planetary interpretation. We performed a global analysis of multi-colour photometric data from TESS and ground-based facilities in order to derive the stellar and planetary physical parameters for each system. We find that TOI-2084 band TOI-4184 bare sub-Neptune-sized planets with radii of Rp = 2.47 ± 0.13Râ and Rp = 2.43 ± 0.21 Râ, respectively. TOI-2084 b completes an orbit around its host star every 6.08 days, has an equilibrium temperature of Teq = 527 ± 8 K and an irradiation of Sp = 12.8 ± 0.8 Sâ. Its host star is a dwarf of spectral M2.0 ± 0.5 at a distance of 114 pc with an effective temperature of Teff = 3550 ± 50 K, and has a wide, co-moving M8 companion at a projected separation of 1400 au. TOI-4184 b orbits around an M5.0 ± 0.5 type dwarf star (Kmag = 11.87) each 4.9 days, and has an equilibrium temperature of Teq = 412 ± 8 K and an irradiation of Sp = 4.8 ± 0.4 Sâ. TOI-4184 is a metal poor star ([Fe/H] = â0.27 ± 0.09 dex) at a distance of 69 pc with an effective temperature of Teff = 3225 ± 75 K. Both planets are located at the edge of the sub-Jovian desert in the radius-period plane. The combination of the small size and the large infrared brightness of their host stars make these new planets promising targets for future atmospheric exploration with JWST.Publisher PDFPeer reviewe
TOI-5678 b: A 48-day transiting Neptune-mass planet characterized with CHEOPS and HARPS
A large sample of long-period giant planets has been discovered thanks to
long-term radial velocity surveys, but only a few dozen of these planets have a
precise radius measurement. Transiting gas giants are crucial targets for the
study of atmospheric composition across a wide range of equilibrium
temperatures and for shedding light on the formation and evolution of planetary
systems. Indeed, compared to hot Jupiters, the atmospheric properties and
orbital parameters of cooler gas giants are unaltered by intense stellar
irradiation and tidal effects. We identify long-period planets in the
Transiting Exoplanet Survey Satellite (TESS) data as duo-transit events. To
solve the orbital periods of TESS duo-transit candidates, we use the
CHaracterising ExOPlanet Satellite (CHEOPS) to observe the highest-probability
period aliases in order to discard or confirm a transit event at a given
period. We also collect spectroscopic observations with CORALIE and HARPS in
order to confirm the planetary nature and measure the mass of the candidates.
We report the discovery of a warm transiting Neptune-mass planet orbiting
TOI-5678. After four non-detections corresponding to possible periods, CHEOPS
detected a transit event matching a unique period alias. Joint modeling reveals
that TOI-5678 hosts a 47.73 day period planet. TOI-5678 b has a mass of 20
(+-4) Me and a radius of 4.91 (+-0.08 Re) . Using interior structure modeling,
we find that TOI-5678 b is composed of a low-mass core surrounded by a large
H/He layer with a mass of 3.2 (+1.7, -1.3) Me. TOI-5678 b is part of a growing
sample of well-characterized transiting gas giants receiving moderate amounts
of stellar insolation (11 Se). Precise density measurement gives us insight
into their interior composition, and the objects orbiting bright stars are
suitable targets to study the atmospheric composition of cooler gas giants.Comment: 17 pages, 10 figures, accepted to A&
Identification of the top TESS objects of interest for atmospheric characterization of transiting exoplanets with JWST
Funding: Funding for the TESS mission is provided by NASA's Science Mission Directorate. This work makes use of observations from the LCOGT network. Part of the LCOGT telescope time was granted by NOIRLab through the Mid-Scale Innovations Program (MSIP). MSIP is funded by NSF. This paper is based on observations made with the MuSCAT3 instrument, developed by the Astrobiology Center and under financial support by JSPS KAKENHI (grant No. JP18H05439) and JST PRESTO (grant No. JPMJPR1775), at Faulkes Telescope North on Maui, HI, operated by the Las Cumbres Observatory. This paper makes use of data from the MEarth Project, which is a collaboration between Harvard University and the Smithsonian Astrophysical Observatory. The MEarth Project acknowledges funding from the David and Lucile Packard Fellowship for Science and Engineering, the National Science Foundation under grant Nos. AST-0807690, AST-1109468, AST-1616624 and AST-1004488 (Alan T. Waterman Award), the National Aeronautics and Space Administration under grant No. 80NSSC18K0476 issued through the XRP Program, and the John Templeton Foundation. C.M. would like to gratefully acknowledge the entire Dragonfly Telephoto Array team, and Bob Abraham in particular, for allowing their telescope bright time to be put to use observing exoplanets. B.J.H. acknowledges support from the Future Investigators in NASA Earth and Space Science and Technology (FINESST) program (grant No. 80NSSC20K1551) and support by NASA under grant No. 80GSFC21M0002. K.A.C. and C.N.W. acknowledge support from the TESS mission via subaward s3449 from MIT. D.R.C. and C.A.C. acknowledge support from NASA through the XRP grant No. 18-2XRP18_2-0007. C.A.C. acknowledges that this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). S.Z. and A.B. acknowledge support from the Israel Ministry of Science and Technology (grant No. 3-18143). The research leading to these results has received funding from the ARC grant for Concerted Research Actions, financed by the Wallonia-Brussels Federation. TRAPPIST is funded by the Belgian Fund for Scientific Research (Fond National de la Recherche Scientifique, FNRS) under the grant No. PDR T.0120.21. The postdoctoral fellowship of K.B. is funded by F.R.S.-FNRS grant No. T.0109.20 and by the Francqui Foundation. H.P.O.'s contribution has been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation under grant Nos. 51NF40_182901 and 51NF40_205606. F.J.P. acknowledges financial support from the grant No. CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033. A.J. acknowledges support from ANIDâMillennium Science InitiativeâICN12_009 and from FONDECYT project 1210718. Z.L.D. acknowledges the MIT Presidential Fellowship and that this material is based upon work supported by the National Science Foundation Graduate Research Fellowship under grant No. 1745302. P.R. acknowledges support from the National Science Foundation grant No. 1952545. This work is partly supported by JSPS KAKENHI grant Nos. JP17H04574, JP18H05439, JP21K20376; JST CREST grant No. JPMJCR1761; and Astrobiology Center SATELLITE Research project AB022006. This publication benefits from the support of the French Community of Belgium in the context of the FRIA Doctoral Grant awarded to M.T. D.D. acknowledges support from TESS Guest Investigator Program grant Nos. 80NSSC22K1353, 80NSSC22K0185, and 80NSSC23K0769. A.B. acknowledges the support of M.V. Lomonosov Moscow State University Program of Development. T.D. was supported in part by the McDonnell Center for the Space Sciences. V.K. acknowledges support from the youth scientific laboratory project, topic FEUZ-2020-0038.JWST has ushered in an era of unprecedented ability to characterize exoplanetary atmospheres. While there are over 5000 confirmed planets, more than 4000 Transiting Exoplanet Survey Satellite (TESS) planet candidates are still unconfirmed and many of the best planets for atmospheric characterization may remain to be identified. We present a sample of TESS planets and planet candidates that we identify as âbest-in-classâ for transmission and emission spectroscopy with JWST. These targets are sorted into bins across equilibrium temperature Teq and planetary radius Rp and are ranked by a transmission and an emission spectroscopy metric (TSM and ESM, respectively) within each bin. We perform cuts for expected signal size and stellar brightness to remove suboptimal targets for JWST. Of the 194 targets in the resulting sample, 103 are unconfirmed TESS planet candidates, also known as TESS Objects of Interest (TOIs). We perform vetting and statistical validation analyses on these 103 targets to determine which are likely planets and which are likely false positives, incorporating ground-based follow-up from the TESS Follow-up Observation Program to aid the vetting and validation process. We statistically validate 18 TOIs, marginally validate 31 TOIs to varying levels of confidence, deem 29 TOIs likely false positives, and leave the dispositions for four TOIs as inconclusive. Twenty-one of the 103 TOIs were confirmed independently over the course of our analysis. We intend for this work to serve as a community resource and motivate formal confirmation and mass measurements of each validated planet. We encourage more detailed analysis of individual targets by the community.Peer reviewe
GJ 3090 b: one of the most favourable mini-Neptune for atmospheric characterisation
We report the detection of GJ 3090 b (TOI-177.01), a mini-Neptune on a 2.9-day orbit transiting a bright (K = 7.3 mag) M2 dwarf located at 22 pc. The planet was identified by the Transiting Exoplanet Survey Satellite and was confirmed with the High Accuracy Radial velocity Planet Searcher radial velocities. Seeing-limited photometry and speckle imaging rule out nearby eclipsing binaries. Additional transits were observed with the LCOGT, Spitzer, and ExTrA telescopes. We characterise the star to have a mass of 0.519 ± 0.013 Mâ and a radius of 0.516 ± 0.016 Râ. We modelled the transit light curves and radial velocity measurements and obtained a planetary mass of 3.34 ± 0.72 ME, a radius of 2.13 ± 0.11 RE, and a mean density of 1.89â0.45+0.52 g cmâ3. The low density of the planet implies the presence of volatiles, and its radius and insolation place it immediately above the radius valley at the lower end of the mini-Neptune cluster. A coupled atmospheric and dynamical evolution analysis of the planet is inconsistent with a pure HâHe atmosphere and favours a heavy mean molecular weight atmosphere. The transmission spectroscopy metric of 221â46+66 means that GJ 3090 b is the second or third most favorable mini-Neptune after GJ 1214 b whose atmosphere may be characterised. At almost half the mass of GJ 1214 b, GJ 3090 b is an excellent probe of the edge of the transition between super-Earths and mini-Neptunes. We identify an additional signal in the radial velocity data that we attribute to a planet candidate with an orbital period of 13 days and a mass of 17.1â3.2+8.9 ME, whose transits are not detected
Three new brown dwarfs and a massive hot Jupiter revealed by TESS around early-type stars
Context. The detection and characterization of exoplanets and brown dwarfs around massive AF-type stars is essential to investigate and constrain the impact of stellar mass on planet properties. However, such targets are still poorly explored in radial velocity (RV) surveys because they only feature a small number of stellar lines and those are usually broadened and blended by stellar rotation as well as stellar jitter. As a result, the available information about the formation and evolution of planets and brown dwarfs around hot stars is limited.
Aims. We aim to increase the sample and precisely measure the masses and eccentricities of giant planets and brown dwarfs transiting early-type stars detected by the Transiting Exoplanet Survey Satellite (TESS).
Methods. We followed bright (V 6200 K that host giant companions (R > 7 Râ) using ground-based photometric observations as well as high precision radial velocity measurements from the CORALIE, CHIRON, TRES, FEROS, and MINERVA-Australis spectrographs.
Results. In the context of the search for exoplanets and brown dwarfs around early-type stars, we present the discovery of three brown dwarf companions, TOI-629b, TOI-1982b, and TOI-2543b, and one massive planet, TOI-1107b. From the joint analysis of TESS and ground-based photometry in combination with high precision radial velocity measurements, we find the brown dwarfs have masses between 66 and 68 MJup, periods between 7.54 and 17.17 days, and radii between 0.95 and 1.11 RJup. The hot Jupiter TOI-1107b has an orbital period of 4.08 days, a radius of 1.30 RJup, and a mass of 3.35 MJup. As a by-product of this program, we identified four low-mass eclipsing components (TOI-288b, TOI-446b, TOI-478b, and TOI-764b).
Conclusions. Both TOI-1107b and TOI-1982b present an anomalously inflated radius with respect to the age of these systems. TOI-629 is among the hottest stars with a known transiting brown dwarf. TOI-629b and TOI-1982b are among the most eccentric brown dwarfs. The massive planet and the three brown dwarfs add to the growing population of well-characterized giant planets and brown dwarfs transiting AF-type stars and they reduce the apparent paucity
Two temperate super-Earths transiting a nearby late-type M dwarf
peer reviewedIn the age of JWST, temperate terrestrial exoplanets transiting nearby late-type M dwarfs provide unique opportunities for characterising their atmospheres, as well as searching for biosignature gases. We report here the discovery and validation of two temperate super-Earths transiting LP 890-9 (TOI-4306, SPECULOOS-2), a relatively low-activity nearby (32 pc) M6V star. The inner planet, LP 890-9b, was first detected by TESS (and identified as TOI-4306.01) based on four sectors of data. Intensive photometric monitoring of the system with the SPECULOOS Southern Observatory then led to the discovery of a second outer transiting planet, LP 890-9c (also identified as SPECULOOS-2c), previously undetected by TESS. The orbital period of this second planet was later confirmed by MuSCAT3 follow-up observations. With a mass of 0.118±0.002 Mâ, a radius of 0.1556±0.0086 Râ, and an effective temperature of 2850±75 K, LP 890-9 is the second-coolest star found to host planets, after TRAPPIST-1. The inner planet has an orbital period of 2.73 d, a radius of 1.320+0.053â0.027 Râ, and receives an incident stellar flux of 4.09±0.12 Sâ. The outer planet has a similar size of 1.367+0.055â0.039 Râ and an orbital period of 8.46 d. With an incident stellar flux of 0.906 ± 0.026 Sâ, it is located within the conservative habitable zone, very close to its inner limit. Although the masses of the two planets remain to be measured, we estimated their potential for atmospheric characterisation via transmission spectroscopy using a mass-radius relationship and found that, after the TRAPPIST-1 planets, LP 890-9c is the second-most favourable habitable-zone terrestrial planet known so far. The discovery of this remarkable system offers another rare opportunity to study temperate terrestrial planets around our smallest and coolest neighbours
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