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The young mini-Neptune HD 207496b that is either a naked core or on the verge of becoming one (2023)
Journal Article
Barros, S. C. C., Demangeon, O. D. S., Armstrong, D. J., Mena, E. D., Acuna, L., Fernandez, J. F., …Winn, J. N. (2023). The young mini-Neptune HD 207496b that is either a naked core or on the verge of becoming one. Astronomy & Astrophysics, 673, Article A4. https://doi.org/10.1051/0004-6361/202245741

Aims. We report the discovery and characterisation of the transiting mini-Neptune HD 207496 b (TOI-1099) as part of a large programme that aims to characterise naked core planets. Methods. We obtained HARPS spectroscopic observations, one grou... Read More about The young mini-Neptune HD 207496b that is either a naked core or on the verge of becoming one.

The TESS Grand Unified Hot Jupiter Survey. II. Twenty New Giant Planets* (2023)
Journal Article
Hellier. (2023). The TESS Grand Unified Hot Jupiter Survey. II. Twenty New Giant Planets*. Astrophysical Journal Supplement, https://doi.org/10.3847/1538-4365/aca286

NASA's Transiting Exoplanet Survey Satellite (TESS) mission promises to improve our understanding of hot Jupiters by providing an all-sky, magnitude-limited sample of transiting hot Jupiters suitable for population studies. Assembling such a sample r... Read More about The TESS Grand Unified Hot Jupiter Survey. II. Twenty New Giant Planets*.

The EBLM project X. benchmark masses, radii and temperatures for two fully convective M-dwarfs using K2 (2023)
Journal Article
Duck, A., Martin, D. V., Gill, S., Armitage, T., Rodríguez Martínez, R., Maxted, P. F. L., …Udry, S. (2023). The EBLM project X. benchmark masses, radii and temperatures for two fully convective M-dwarfs using K2. Monthly Notices of the Royal Astronomical Society, 521(4), 6305-6317. https://doi.org/10.1093/mnras/stad452

M-dwarfs are the most abundant stars in the galaxy and popular targets for exoplanet searches. However, their intrinsic faintness and complex spectra inhibit precise characterisation. We only know of dozens of M-dwarfs with fundamental parameters of... Read More about The EBLM project X. benchmark masses, radii and temperatures for two fully convective M-dwarfs using K2.

TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf (2023)
Journal Article
Hawthorn, F., Bayliss, D., Wilson, T. G., Bonfanti, A., Adibekyan, V., Alibert, Y., …Zhang, H. (2023). TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf. Monthly Notices of the Royal Astronomical Society, 520(3), 3649 - 3668. https://doi.org/10.1093/mnras/stad306

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... Read More about TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf.

TOI-1075 b: A Dense, Massive, Ultra-short-period Hot Super-Earth Straddling the Radius Gap (2023)
Journal Article
Hellier. (2023). TOI-1075 b: A Dense, Massive, Ultra-short-period Hot Super-Earth Straddling the Radius Gap. Astronomical Journal, https://doi.org/10.3847/1538-3881/ac9c5b

Populating the exoplanet mass–radius diagram in order to identify the underlying relationship that governs planet composition is driving an interdisciplinary effort within the exoplanet community. The discovery of hot super-Earths—a high-temperature,... Read More about TOI-1075 b: A Dense, Massive, Ultra-short-period Hot Super-Earth Straddling the Radius Gap.

TOI-969: a late-K dwarf with a hot mini-Neptune in the desert and an eccentric cold Jupiter (2023)
Journal Article
Hellier. (2023). TOI-969: a late-K dwarf with a hot mini-Neptune in the desert and an eccentric cold Jupiter. Astronomy & Astrophysics, https://doi.org/10.1051/0004-6361/202243879

Context. The current architecture of a given multi-planetary system is a key fingerprint of its past formation and dynamical evolution history. Long-term follow-up observations are key to complete their picture. Aims. In this paper, we focus on the c... Read More about TOI-969: a late-K dwarf with a hot mini-Neptune in the desert and an eccentric cold Jupiter.

Examining the orbital decay targets KELT-9 b, KELT-16 b, and WASP-4 b, and the transit-timing variations of HD 97658 b (2023)
Journal Article
Maxted, P., & Hellier, C. (2023). Examining the orbital decay targets KELT-9 b, KELT-16 b, and WASP-4 b, and the transit-timing variations of HD 97658 b. Astronomy & Astrophysics, 669, Article A124. https://doi.org/10.1051/0004-6361/202244529

Context. Tidal orbital decay is suspected to occur for hot Jupiters in particular, with the only observationally confirmed case of this being WASP-12b. By examining this effect, information on the properties of the host star can be obtained using the... Read More about Examining the orbital decay targets KELT-9 b, KELT-16 b, and WASP-4 b, and the transit-timing variations of HD 97658 b.

TOI 560: Two Transiting Planets Orbiting a K Dwarf Validated with iSHELL, PFS, and HIRES RVs (2023)
Journal Article
Hellier. (2023). TOI 560: Two Transiting Planets Orbiting a K Dwarf Validated with iSHELL, PFS, and HIRES RVs. Astronomical Journal, https://doi.org/10.3847/1538-3881/ac9834

We validate the presence of a two-planet system orbiting the 0.15–1.4 Gyr K4 dwarf TOI 560 (HD 73583). The system consists of an inner moderately eccentric transiting mini-Neptune (TOI 560 b, $P={6.3980661}_{-0.0000097}^{+0.0000095}$ days, $e={0.294}... Read More about TOI 560: Two Transiting Planets Orbiting a K Dwarf Validated with iSHELL, PFS, and HIRES RVs.

The GAPS programme at TNG XL. A puffy and warm Neptune-sized planet and an outer Neptune-mass candidate orbiting the solar-type star TOI-1422 (2022)
Journal Article
Hellier. (2022). The GAPS programme at TNG XL. A puffy and warm Neptune-sized planet and an outer Neptune-mass candidate orbiting the solar-type star TOI-1422. Astronomy & Astrophysics, https://doi.org/10.1051/0004-6361/202244079

Context. Neptunes represent one of the main types of exoplanets and have chemical-physical characteristics halfway between rocky and gas giant planets. Therefore, their characterization is important for understanding and constraining both the formati... Read More about The GAPS programme at TNG XL. A puffy and warm Neptune-sized planet and an outer Neptune-mass candidate orbiting the solar-type star TOI-1422.

GJ 3090 b: one of the most favourable mini-Neptune for atmospheric characterisation (2022)
Journal Article
Hellier. (2022). GJ 3090 b: one of the most favourable mini-Neptune for atmospheric characterisation. Astronomy & Astrophysics, https://doi.org/10.1051/0004-6361/202243975

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 A... Read More about GJ 3090 b: one of the most favourable mini-Neptune for atmospheric characterisation.

The HD 260655 system: Two rocky worlds transiting a bright M dwarf at 10 pc (2022)
Journal Article
Hellier. (2022). The HD 260655 system: Two rocky worlds transiting a bright M dwarf at 10 pc. Astronomy & Astrophysics, 1 - 23. https://doi.org/10.1051/0004-6361/202243834

We report the discovery of a multiplanetary system transiting the M0 V dwarf HD 260655 (GJ 239, TOI-4599). The system consists of at least two transiting planets, namely HD 260655 b, with a period of 2.77 d, a radius of Rb = 1.240 ± 0.023 R?, a mass... Read More about The HD 260655 system: Two rocky worlds transiting a bright M dwarf at 10 pc.

TOI-712: A System of Adolescent Mini-Neptunes Extending to the Habitable Zone (2022)
Journal Article
Hellier. (2022). TOI-712: A System of Adolescent Mini-Neptunes Extending to the Habitable Zone. Astronomical Journal, https://doi.org/10.3847/1538-3881/ac7954

As an all-sky survey, NASA's Transiting Exoplanet Survey Satellite (TESS) mission is able to detect the brightest and rarest types of transiting planetary systems, including young planets that enable study of the evolutionary processes that occur wit... Read More about TOI-712: A System of Adolescent Mini-Neptunes Extending to the Habitable Zone.

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)
Journal Article
Hellier. (2022). 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. Monthly Notices of the Royal Astronomical Society, 1606 - 1627. https://doi.org/10.1093/mnras/stac638

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 foll... Read More about 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.

BEBOP II: sensitivity to sub-Saturn circumbinary planets using radial-velocities (2022)
Journal Article
Maxted, & Hellier. (2022). BEBOP II: sensitivity to sub-Saturn circumbinary planets using radial-velocities. Monthly Notices of the Royal Astronomical Society, 3571 - 3583. https://doi.org/10.1093/mnras/stac113

BEBOP is a radial-velocity survey that monitors a sample of single-lined eclipsing binaries, in search of circumbinary planets by using high-resolution spectrographs. Here, we describe and test the methods we use to identify planetary signals within... Read More about BEBOP II: sensitivity to sub-Saturn circumbinary planets using radial-velocities.

TOI-1201 b: A mini-Neptune transiting a bright and moderately young M dwarf (2021)
Journal Article
Hellier. (2021). TOI-1201 b: A mini-Neptune transiting a bright and moderately young M dwarf. Astronomy & Astrophysics, https://doi.org/10.1051/0004-6361/202141587

We present the discovery of a transiting mini-Neptune around TOI-1201, a relatively bright and moderately young early M dwarf (J ˜ 9.5 mag, ~600–800 Myr) in an equal-mass ~8 arcsecond-wide binary system, using data from the Transiting Exoplanet Surve... Read More about TOI-1201 b: A mini-Neptune transiting a bright and moderately young M dwarf.

GJ 367b: A dense, ultrashort-period sub-Earth planet transiting a nearby red dwarf star. (2021)
Journal Article
Hellier. (2021). GJ 367b: A dense, ultrashort-period sub-Earth planet transiting a nearby red dwarf star. Science, 1271 - 1275. https://doi.org/10.1126/science.aay3253

Ultrashort-period (USP) exoplanets have orbital periods shorter than 1 day. Precise masses and radii of USP exoplanets could provide constraints on their unknown formation and evolution processes. We report the detection and characterization of the U... Read More about GJ 367b: A dense, ultrashort-period sub-Earth planet transiting a nearby red dwarf star..

TIC 172900988: A Transiting Circumbinary Planet Detected in One Sector of TESS Data (2021)
Journal Article
Hellier, & Maxted. (2021). TIC 172900988: A Transiting Circumbinary Planet Detected in One Sector of TESS Data. Astronomical Journal, https://doi.org/10.3847/1538-3881/ac223a

We report the first discovery of a transiting circumbinary planet detected from a single sector of Transiting Exoplanet Survey Satellite (TESS) data. During Sector 21, the planet TIC 172900988b transited the primary star and then five days later it t... Read More about TIC 172900988: A Transiting Circumbinary Planet Detected in One Sector of TESS Data.

The EBLM project - VIII. First results for M-dwarf mass, radius, and effective temperature measurements using CHEOPS light curves (2021)
Journal Article
Hellier, & Maxted. (2021). The EBLM project - VIII. First results for M-dwarf mass, radius, and effective temperature measurements using CHEOPS light curves. Monthly Notices of the Royal Astronomical Society, 306 - 322. https://doi.org/10.1093/mnras/stab1687

The accuracy of theoretical mass, radius, and effective temperature values for M-dwarf stars is an active topic of debate. Differences between observed and theoretical values have raised the possibility that current theoretical stellar structure and... Read More about The EBLM project - VIII. First results for M-dwarf mass, radius, and effective temperature measurements using CHEOPS light curves.