ORCID Profile
0000-0003-0030-332X
Current Organisation
University of Cambridge
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Publisher: EDP Sciences
Date: 04-2020
DOI: 10.1051/0004-6361/201937409
Abstract: Thermal inversions have long been predicted to exist in the atmospheres of ultra-hot Jupiters. However, the detection of two species thought to be responsible – titanium oxide and vanadium oxide – remains elusive. We present a search for TiO and VO in the atmosphere of the ultra-hot Jupiter WASP-121b ( T eq ≳ 2400 K), an exoplanet with evidence of VO in its atmosphere at low resolution which also exhibits water emission features in its dayside spectrum characteristic of a temperature inversion. We observed its transmission spectrum with the UV-Visual Echelle Spectrograph at the Very Large Telescope and used the cross-correlation method – a powerful tool for the unambiguous identification of the presence of atomic and molecular species – in an effort to detect whether TiO or VO were responsible for the observed temperature inversion. No evidence for the presence of TiO or VO was found at the terminator of WASP-121b. By injecting signals into our data at varying abundance levels, we set rough detection limits of [VO] ≲−7.9 and [TiO] ≲−9.3. However, these detection limits are largely degenerate with scattering properties and the position of the cloud deck. Our results may suggest that neither TiO or VO are the main drivers of the thermal inversion in WASP-121b however, until a more accurate line list is developed for VO, we cannot conclusively rule out its presence. Future works will consist of a search for other strong optically-absorbing species that may be responsible for the excess absorption in the red-optical.
Publisher: American Astronomical Society
Date: 20-09-2023
Publisher: EDP Sciences
Date: 12-2022
DOI: 10.1051/0004-6361/202243720
Abstract: Context. The HD 108236 system was first announced with the detection of four small planets based on TESS data. Shortly after, the transit of an additional planet with a period of 29.54 d was serendipitously detected by CHEOPS. In this way, HD 108236 (V = 9.2) became one of the brightest stars known to host five small transiting planets ( R p 3 R ⊕ ). Aims. We characterize the planetary system by using all the data available from CHEOPS and TESS space missions. We use the flexible pointing capabilities of CHEOPS to follow up the transits of all the planets in the system, including the fifth transiting body. Methods. After updating the host star parameters by using the results from Gaia eDR3, we analyzed 16 and 43 transits observed by CHEOPS and TESS, respectively, to derive the planets’ physical and orbital parameters. We carried out a timing analysis of the transits of each of the planets of HD 108236 to search for the presence of transit timing variations. Results. We derived improved values for the radius and mass of the host star ( R ★ = 0.876 ± 0.007 R 0 and M ★ = 0.867 -0.046 +0.047 M ⊙). We confirm the presence of the fifth transiting planet f in a 29.54 d orbit. Thus, the HD 108236 system consists of five planets of R b = 1.587±0.028, R c = 2.122±0.025, R d = 2.629 ± 0.031, R e = 3.008 ± 0.032, and R f = 1.89 ± 0.04 [ R ⊕ ]. We refine the transit ephemeris for each planet and find no significant transit timing variations for planets c, d , and e . For planets b and f , instead, we measure significant deviations on their transit times (up to 22 and 28 min, respectively) with a non-negligible dispersion of 9.6 and 12.6 min in their time residuals. Conclusions. We confirm the presence of planet f and find no significant evidence for a potential transiting planet in a 10.9 d orbital period, as previously suggested. Further monitoring of the transits, particularly for planets b and f , would confirm the presence of the observed transit time variations. HD 108236 thus becomes a key multi-planetary system for the study of formation and evolution processes. The reported precise results on the planetary radii – together with a profuse RV monitoring – will allow for an accurate characterization of the internal structure of these planets.
Publisher: EDP Sciences
Date: 2023
DOI: 10.1051/0004-6361/202244529
Abstract: 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 so-called stellar modified tidal quality factor Q * ′ , which describes the efficiency with which the kinetic energy of the planet is dissipated within the star. This can provide information about the interior of the star. Aims. In this study, we aim to improve constraints on the tidal decay of the KELT-9, KELT-16, and WASP-4 systems in order to find evidence for or against the presence of tidal orbital decay. With this, we want to constrain the Q * ′ value for each star. In addition, we aim to test the existence of the transit timing variations (TTVs) in the HD 97658 system, which previously favoured a quadratic trend with increasing orbital period. Methods. Making use of newly acquired photometric observations from CHEOPS (CHaracterising ExOplanet Satellite) and TESS (Transiting Exoplanet Survey Satellite), combined with archival transit and occultation data, we use Markov chain Monte Carlo (MCMC) algorithms to fit three models to the data, namely a constant-period model, an orbital-decay model, and an apsidal-precession model. Results. We find that the KELT-9 system is best described by an apsidal-precession model for now, with an orbital decay trend at over 2 σ being a possible solution as well. A Keplerian orbit model with a constant orbital period provides the best fit to the transit timings of KELT-16 b because of the scatter and scale of their error bars. The WASP-4 system is best represented by an orbital decay model at a 5 σ significance, although apsidal precession cannot be ruled out with the present data. For HD 97658 b, using recently acquired transit observations, we find no conclusive evidence for a previously suspected strong quadratic trend in the data.
Publisher: Oxford University Press (OUP)
Date: 28-01-2022
Abstract: We present a precise characterization of the TOI-561 planetary system obtained by combining previously published data with TESS and CHEOPS photometry, and a new set of 62 HARPS-N radial velocities (RVs). Our joint analysis confirms the presence of four transiting planets, namely TOI-561 b (P = 0.45 d, R = 1.42 R⊕, M = 2.0 M⊕), c (P = 10.78 d, R = 2.91 R⊕, M = 5.4 M⊕), d (P = 25.7 d, R = 2.82 R⊕, M = 13.2 M⊕), and e (P = 77 d, R = 2.55 R⊕, M = 12.6 R⊕). Moreover, we identify an additional, long-period signal (& d) in the RVs, which could be due to either an external planetary companion or to stellar magnetic activity. The precise masses and radii obtained for the four planets allowed us to conduct interior structure and atmospheric escape modelling. TOI-561 b is confirmed to be the lowest density (ρb = 3.8 ± 0.5 g cm−3) ultra-short period (USP) planet known to date, and the low metallicity of the host star makes it consistent with the general bulk density-stellar metallicity trend. According to our interior structure modelling, planet b has basically no gas envelope, and it could host a certain amount of water. In contrast, TOI-561 c, d, and e likely retained an H/He envelope, in addition to a possibly large water layer. The inferred planetary compositions suggest different atmospheric evolutionary paths, with planets b and c having experienced significant gas loss, and planets d and e showing an atmospheric content consistent with the original one. The uniqueness of the USP planet, the presence of the long-period planet TOI-561 e, and the complex architecture make this system an appealing target for follow-up studies.
Publisher: Oxford University Press (OUP)
Date: 20-11-2019
Abstract: We report the discovery, by the Next Generation Transit Survey (NGTS), of two hot-Jupiters NGTS-8b and NGTS-9b. These orbit a $V\\, =\\, 13.68$ K0V star (Teff = 5241 ± 50 K) with a period of 2.49970 days, and a $V\\, =\\, 12.80$ F8V star (Teff = 6330 ± 130 K) in 4.43527 days, respectively. The transits were independently verified by follow-up photometric observations with the SAAO 1.0-m and Euler telescopes, and we report on the planetary parameters using HARPS, FEROS and CORALIE radial velocities. NGTS-8b has a mass, $0.93\\, ^{+0.04}_{-0.03}$ MJ and a radius, 1.09 ± 0.03 RJ similar to Jupiter, resulting in a density of $0.89\\, ^{+0.08}_{-0.07}$ g cm−3. This is in contrast to NGTS-9b, which has a mass of 2.90 ± 0.17 MJ and a radius of 1.07 ± 0.06 RJ, resulting in a much greater density of $2.93^{+0.53}_{-0.49}$ g cm−3. Statistically, the planetary parameters put both objects in the regime where they would be expected to exhibit larger than predicted radii. However, we find that their radii are in agreement with predictions by theoretical non-inflated models.
Publisher: Springer Science and Business Media LLC
Date: 13-10-2020
Publisher: American Astronomical Society
Date: 08-2022
Abstract: We report the discovery in TESS data and validation of HD 56414 b (a.k.a. TOI-1228 b), a Neptune-size ( R p = 3.71 ± 0.20 R ⊕ ) planet with a 29 day orbital period transiting a young (age = 420 ± 140 Myr) A-type star in the TESS southern continuous-viewing zone. HD 56414 is one of the hottest stars ( T eff = 8500 ± 150 K) to host a known sub-Jovian planet. HD 56414 b lies on the boundary of the hot Neptune desert in the planet radius–bolometric insolation flux space, suggesting that the planet may be experiencing mass loss. To explore this, we apply a photoevaporation model that incorporates the high near-ultraviolet continuum emission of A-type stars. We find that the planet can retain most of its atmosphere over the typical 1 Gyr main-sequence lifetime of an A-type star if its mass is ≥8 M ⊕ . Our model also predicts that close-in Neptune-size planets with masses M ⊕ are susceptible to total atmospheric stripping over 1 Gyr, hinting that the hot Neptune desert, which has been previously observed around FGKM-type stars, likely extends to A-type stars.
Publisher: Oxford University Press (OUP)
Date: 20-02-2020
Abstract: We report the discovery of a new ultrashort period (USP) transiting hot Jupiter from the Next Generation Transit Survey (NGTS). NGTS-10b has a mass and radius of $2.162\\, ^{+0.092}_{-0.107}$ MJ and $1.205\\, ^{+0.117}_{-0.083}$ RJ and orbits its host star with a period of 0.7668944 ± 0.0000003 d, making it the shortest period hot Jupiter yet discovered. The host is a 10.4 ± 2.5 Gyr old K5V star (Teff = 4400 ± 100 K) of Solar metallicity ([Fe/H] = −0.02 ± 0.12 dex) showing moderate signs of stellar activity. NGTS-10b joins a short list of USP Jupiters that are prime candidates for the study of star–planet tidal interactions. NGTS-10b orbits its host at just 1.46 ± 0.18 Roche radii, and we calculate a median remaining inspiral time of 38 Myr and a potentially measurable orbital period decay of 7 s over the coming decade, assuming a stellar tidal quality factor $Q^{\\prime }_{\\rm s}$ =2 × 107.
Publisher: American Astronomical Society
Date: 06-2023
Abstract: We present the discovery and characterization of HIP 33609 b, a transiting warm brown dwarf orbiting a late B star, discovered by NASA's Transiting Exoplanet Survey Satellite as TOI-588 b. HIP 33609 b is a large ( R b = 1.580 − 0.070 + 0.074 R J ) brown dwarf on a highly eccentric ( e = 0.560 − 0.031 + 0.029 ) orbit with a 39 days period. The host star is a bright ( V = 7.3 mag), T eff = 10,400 − 660 + 800 K star with a mass of M * = 2.383 − 0.095 + 0.10 M ⊙ and radius of R * = 1.863 − 0.082 + 0.087 R ⊙ , making it the hottest transiting brown dwarf host star discovered to date. We obtained radial velocity measurements from the CHIRON spectrograph confirming the companion's mass of M b = 68.0 − 7.1 + 7.4 M J as well as the host star's rotation rate ( v sin i * = 55.6 ± 1.8 km s −1 ). We also present the discovery of a new comoving group of stars, designated as MELANGE-6, and determine that HIP 33609 is a member. We use a combination of rotation periods and isochrone models fit to the cluster members to estimate an age of 150 ± 25 Myr. With a measured mass, radius, and age, HIP 33609 b becomes a benchmark for substellar evolutionary models.
Publisher: Springer Science and Business Media LLC
Date: 14-09-2020
Publisher: American Astronomical Society
Date: 30-05-2022
Abstract: The Kepler and TESS missions have demonstrated that planets are ubiquitous. However, the success of these missions heavily depends on ground-based radial velocity (RV) surveys, which combined with transit photometry can yield bulk densities and orbital properties. While most Kepler host stars are too faint for detailed follow-up observations, TESS is detecting planets orbiting nearby bright stars that are more amenable to RV characterization. Here, we introduce the TESS-Keck Survey (TKS), an RV program using ∼100 nights on Keck/HIRES to study exoplanets identified by TESS. The primary survey aims are investigating the link between stellar properties and the compositions of small planets studying how the ersity of system architectures depends on dynamical configurations or planet multiplicity identifying prime candidates for atmospheric studies with JWST and understanding the role of stellar evolution in shaping planetary systems. We present a fully automated target selection algorithm, which yielded 103 planets in 86 systems for the final TKS s le. Most TKS hosts are inactive, solar-like, main-sequence stars (4500 K ≤ T eff K) at a wide range of metallicities. The selected TKS s le contains 71 small planets ( R p ≤ 4 R ⊕ ), 11 systems with multiple transiting candidates, six sub-day-period planets and three planets that are in or near the habitable zone ( S inc ≤ 10 S ⊕ ) of their host star. The target selection described here will facilitate the comparison of measured planet masses, densities, and eccentricities to predictions from planet population models. Our target selection software is publicly available and can be adapted for any survey that requires a balance of multiple science interests within a given telescope allocation.
Publisher: EDP Sciences
Date: 28-10-2022
DOI: 10.1051/0004-6361/202243093
Abstract: We present the discovery of two small planets transiting HD 93963A (TOI-1797), a GOV star ( M * = 1.109 ± 0.043 M ⊙ , R * = 1.043 ± 0.009 R ⊙ ) in a visual binary system. We combined TESS and CHEOPS space-borne photometry with MuSCAT 2 ground-based photometry, ‘Alopeke and PHARO high-resolution imaging, TRES and FIES reconnaissance spectroscopy, and SOPHIE radial velocity measurements. We validated and spectroscopically confirmed the outer transiting planet HD 93963 A c, a sub-Neptune with an orbital period of P c ≈ 3.65 d that was reported to be a TESS object of interest (TOI) shortly after the release of Sector 22 data. HD 93963 A c has amass of M c = 19.2 ± 4.1 M ⊕ and a radius of R c = 3.228 ± 0.059 R ⊕ , implying a mean density of ρ c = 3.1 ± 0.7 g cm -3 . The inner object, HD 93963 A b, is a validated 1.04 d ultra-short period (USP) transiting super-Earth that we discovered in the TESS light curve and that was not listed as a TOI, owing to the low significance of its signal (TESS signal-to-noise ratio ≈6.7, TESS + CHEOPS combined transit depth D b = 141.5 −8.3 +8.5 ppm). We intensively monitored the star with CHEOPS by performing nine transit observations to confirm the presence of the inner planet and validate the system. HD 93963 A b is the first small ( R b = 1.35 ± 0.042 R ⊕ ) USP planet discovered and validated by TESS and CHEOPS. Unlike planet c, HD 93963 Ab is not significantly detected in our radial velocities ( M b = 7.8 ± 3.2 M ⊕ ). The two planets are on either side of the radius valley, implying that they could have undergone completely different evolution processes. We also discovered a linear trend in our Doppler measurements, suggesting the possible presence of a long-period outer planet. With a V -band magnitude of 9.2, HD 93963 A is among the brightest stars known to host a USP planet, making it one of the most favourable targets for precise mass measurement via Doppler spectroscopy and an important laboratory to test formation, evolution, and migration models of planetary systems hosting ultra-short period planets.
Publisher: Oxford University Press (OUP)
Date: 02-07-2021
Abstract: Ultrahot Jupiters (UHJs) present excellent targets for atmospheric characterization. Their hot dayside temperatures (T ≳ 2200 K) strongly suppress the formation of condensates, leading to clear and highly inflated atmospheres extremely conducive to transmission spectroscopy. Recent studies using optical high-resolution spectra have discovered a plethora of neutral and ionized atomic species in UHJs, placing constraints on their atmospheric structure and composition. Our recent work has presented a search for molecular features and detection of Fe i in the UHJ WASP-121b using Very Large Telescope (VLT)/UV–Visual Echelle Spectrograph (UVES) transmission spectroscopy. Here, we present a systematic search for atomic species in its atmosphere using cross-correlation methods. In a single transit, we uncover potential signals of 17 atomic species that we investigate further, categorizing five as strong detections, three as tentative detections, and nine as weak signals worthy of further exploration. We confirm previous detections of Cr i, V i, Ca i, K i, and exospheric H i and Ca ii made with the High Accuracy Radial velocity Planet Searcher (HARPS) and the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO), and independently re-recover our previous detection of Fe i at 8.8σ using both the blue and red arms of the UVES data. We also add a novel detection of Sc ii at 4.2σ. Our results further demonstrate the richness of UHJs for optical high-resolution spectroscopy.
Publisher: EDP Sciences
Date: 06-2023
DOI: 10.1051/0004-6361/202345943
Abstract: Context . Multi-planet systems are important sources of information regarding the evolution of planets. However, the long-period planets in these systems often escape detection. These objects in particular may retain more of their primordial characteristics compared to close-in counterparts because of their increased distance from the host star. HD 22946 is a bright ( G = 8.13 mag) late F-type star around which three transiting planets were identified via Transiting Exoplanet Survey Satellite (TESS) photometry, but the true orbital period of the outermost planet d was unknown until now. Aims . We aim to use the Characterising Exoplanet Satellite (CHEOPS) space telescope to uncover the true orbital period of HD 22946d and to refine the orbital and planetary properties of the system, especially the radii of the planets. Methods . We used the available TESS photometry of HD 22946 and observed several transits of the planets b, c, and d using CHEOPS. We identified two transits of planet d in the TESS photometry, calculated the most probable period aliases based on these data, and then scheduled CHEOPS observations. The photometric data were supplemented with ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) radial velocity data. Finally, a combined model was fitted to the entire dataset in order to obtain final planetary and system parameters. Results . Based on the combined TESS and CHEOPS observations, we successfully determined the true orbital period of the planet d to be 47.42489 ± 0.00011 days, and derived precise radii of the planets in the system, namely 1.362 ± 0.040 R ⊕ , 2.328 ± 0.039 R ⊕ , and 2.607 ± 0.060 R ⊕ for planets b, c, and d, respectively. Due to the low number of radial velocities, we were only able to determine 3 σ upper limits for these respective planet masses, which are 13.71 M ⊕ , 9.72 M ⊕ , and 26.57 M ⊕ . We estimated that another 48 ESPRESSO radial velocities are needed to measure the predicted masses of all planets in HD 22946. We also derived stellar parameters for the host star. Conclusions . Planet c around HD 22946 appears to be a promising target for future atmospheric characterisation via transmission spectroscopy. We can also conclude that planet d, as a warm sub-Neptune, is very interesting because there are only a few similar confirmed exoplanets to date. Such objects are worth investigating in the near future, for ex le in terms of their composition and internal structure.
Publisher: Oxford University Press (OUP)
Date: 20-09-2018
Publisher: EDP Sciences
Date: 03-2023
DOI: 10.1051/0004-6361/202244790
Abstract: The planetary system around the naked-eye star v 2 Lupi (HD 136352 TOI-2011) is composed of three exoplanets with masses of 4.7, 11.2, and 8.6 Earth masses ( M ⊕ ). The TESS and CHEOPS missions revealed that all three planets are transiting and have radii straddling the radius gap separating volatile-rich and volatile-poor super-earths. Only a partial transit of planet d had been covered so we re-observed an inferior conjunction of the long-period 8.6 M ⊕ exoplanet v 2 Lup d with the CHEOPS space telescope. We confirmed its transiting nature by covering its whole 9.1 h transit for the first time. We refined the planet transit ephemeris to P = 107.1361 −0.0022 +0.0019 days and T c = 2459009.7759 −0.0096 +0.0101 BJD TDB , improving by ~40 times on the previously reported transit timing uncertainty. This refined ephemeris will enable further follow-up of this outstanding long-period transiting planet to search for atmospheric signatures or explore the planet’s Hill sphere in search for an exomoon. In fact, the CHEOPS observations also cover the transit of a large fraction of the planet’s Hill sphere, which is as large as the Earth’s, opening the tantalising possibility of catching transiting exomoons. We conducted a search for exomoon signals in this single-epoch light curve but found no conclusive photometric signature of additional transiting bodies larger than Mars. Yet, only a sustained follow-up of v 2 Lup d transits will warrant a comprehensive search for a moon around this outstanding exoplanet.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Matthew Hooton.