ORCID Profile
0000-0002-3012-0316
Current Organisations
University of Cambridge
,
ETH Zurich
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Publisher: American Astronomical Society
Date: 14-01-2016
Publisher: Oxford University Press (OUP)
Date: 14-03-2019
DOI: 10.1093/MNRAS/STZ742
Publisher: Oxford University Press (OUP)
Date: 13-09-2018
Publisher: EDP Sciences
Date: 10-2022
DOI: 10.1051/0004-6361/202243583
Abstract: Context. Long-period transiting planets provide the opportunity to better understand the formation and evolution of planetary systems. Their atmospheric properties remain largely unaltered by tidal or radiative effects of the host star, and their orbital arrangement reflects a different and less extreme migrational history compared to close-in objects. The s le of long-period exoplanets with well-determined masses and radii is still limited, but a growing number of long-period objects reveal themselves in the Transiting Exoplanet Survey Satellite (TESS) data. Aims. Our goal is to vet and confirm single-transit planet candidates detected in the TESS space-based photometric data through spectroscopic and photometric follow-up observations with ground-based instruments. Methods. We used high-resolution spectrographs to confirm the planetary nature of the transiting candidates and measure their masses. We also used the Next Generation Transit Survey (NGTS) to photometrically monitor the candidates in order to observe additional transits. Using a joint modeling of the light curves and radial velocities, we computed the orbital parameters of the system and were able to precisely measure the mass and radius of the transiting planets. Results. We report the discovery of two massive, warm Jupiter-size planets, one orbiting the F8-type star TOI-5153 and the other orbiting the G1-type star NGTS-20 (=TOI-5152). From our spectroscopic analysis, both stars are metal rich with a metallicity of 0.12 and 0.15, respectively. Only TOI-5153 presents a second transit in the TESS extended mission data, but NGTS observed NGTS-20 as part of its mono-transit follow-up program and detected two additional transits. Follow-up high-resolution spectroscopic observations were carried out with CORALIE, CHIRON, FEROS, and HARPS. TOI-5153 hosts a planet with a period of 20.33 days, a planetary mass of 3.26 −0.17 +0.18 Jupiter masses ( M J ), a radius of 1.06 −0.04 +0.04 R J , and an orbital eccentricity of 0.091 −0.026 +0.024 . NGTS-20 b is a 2.98 −0.15 +0.16 M J planet with a radius of 1.07 −0.04 +0.04 R J on an eccentric 0.432 −0.023 +0.023 orbit with an orbital period of 54.19 days. Both planets are metal enriched and their heavy element content is in line with the previously reported mass-metallicity relation for gas giants. Conclusions. Both warm Jupiters orbit moderately bright host stars, making these objects valuable targets for follow-up studies of the planetary atmosphere and measurement of the spin-orbit angle of the system.
Publisher: Oxford University Press (OUP)
Date: 03-11-2017
Publisher: Oxford University Press (OUP)
Date: 27-08-2019
Abstract: We report the discovery of a new ultrashort period hot Jupiter from the Next Generation Transit Survey. NGTS-6b orbits its star with a period of 21.17 h, and has a mass and radius of $1.330^{+0.024}_{-0.028}$MJ and $1.271^{+0.197}_{-0.188}$RJ, respectively, returning a planetary bulk density of $0.711^{+0.214}_{-0.136}$ g cm−3. Conforming to the currently known small population of ultrashort period hot Jupiters, the planet appears to orbit a metal-rich star ([Fe/H] = +0.11 ± 0.09 dex). Photoevaporation models suggest the planet should have lost 5 per cent of its gaseous atmosphere over the course of the 9.6 Gyr of evolution of the system. NGTS-6b adds to the small, but growing list of ultrashort period gas giant planets, and will help us to understand the dominant formation and evolutionary mechanisms that govern this population.
Publisher: Oxford University Press (OUP)
Date: 26-07-2019
Abstract: SuperWASP, the Northern hemisphere WASP observatory, has been observing the skies from La Palma since 2004. In that time, more than 50 planets have been discovered with data contributions from SuperWASP. In the process of validating planets, many false-positive candidates have also been identified. The TESS telescope is set to begin observations of the northern sky in 2019. Similar to the WASP survey, the TESS pixel size is relatively large (13 arcsec for WASP and 21 arcsec for TESS), making it susceptible to many blended signals and false detections caused principally by grazing and blended stellar eclipsing binary systems. In order to reduce duplication of effort on targets, we present a catalogue of 1 041 Northern hemisphere SuperWASP targets that have been rejected as planetary transits through follow-up observation.
Publisher: American Astronomical Society
Date: 22-01-2021
DOI: 10.3847/PSJ/ABD022
Abstract: We have collected transit times for the TRAPPIST-1 system with the Spitzer Space Telescope over four years. We add to these ground-based, HST, and K2 transit-time measurements, and revisit an N -body dynamical analysis of the seven-planet system using our complete set of times from which we refine the mass ratios of the planets to the star. We next carry out a photodynamical analysis of the Spitzer light curves to derive the density of the host star and the planet densities. We find that all seven planets’ densities may be described with a single rocky mass–radius relation which is depleted in iron relative to Earth, with Fe 21 wt% versus 32 wt% for Earth, and otherwise Earth-like in composition. Alternatively, the planets may have an Earth-like composition but enhanced in light elements, such as a surface water layer or a core-free structure with oxidized iron in the mantle. We measure planet masses to a precision of 3%–5%, equivalent to a radial-velocity (RV) precision of 2.5 cm s −1 , or two orders of magnitude more precise than current RV capabilities. We find the eccentricities of the planets are very small, the orbits are extremely coplanar, and the system is stable on 10 Myr timescales. We find evidence of infrequent timing outliers, which we cannot explain with an eighth planet we instead account for the outliers using a robust likelihood function. We forecast JWST timing observations and speculate on possible implications of the planet densities for the formation, migration, and evolution of the planet system.
Publisher: Oxford University Press (OUP)
Date: 17-05-2019
Abstract: The TRAPPIST-1 planetary system is a favourable target for the atmospheric characterization of temperate earth-sized exoplanets by means of transmission spectroscopy with the forthcoming James Webb Space Telescope (JWST). A possible obstacle to this technique could come from the photospheric heterogeneity of the host star that could affect planetary signatures in the transit transmission spectra. To constrain further this possibility, we gathered an extensive photometric data set of 25 TRAPPIST-1 transits observed in the near-IR J band (1.2 μm) with the UKIRT and the AAT, and in the NB2090 band (2.1 μm) with the VLT during the period 2015–18. In our analysis of these data, we used a special strategy aiming to ensure uniformity in our measurements and robustness in our conclusions. We reach a photometric precision of 0.003 (RMS of the residuals), and we detect no significant temporal variations of transit depths of TRAPPIST-1 b, c, e, and g over the period of 3 yr. The few transit depths measured for planets d and f hint towards some level of variability, but more measurements will be required for confirmation. Our depth measurements for planets b and c disagree with the stellar contamination spectra originating from the possible existence of bright spots of temperature 4500 K. We report updated transmission spectra for the six inner planets of the system which are globally flat for planets b and g and some structures are seen for planets c, d, e, and f.
Publisher: EDP Sciences
Date: 09-2011
Publisher: Oxford University Press (OUP)
Date: 07-07-2020
Abstract: We present the detection of high-energy white-light flares from pre-main-sequence stars associated with the Orion Complex, observed as part of the Next Generation Transit Survey (NGTS). With energies up to 5.2 × 1035 erg these flares are some of the most energetic white-light flare events seen to date. We have used the NGTS observations of flaring and non-flaring stars to measure the average flare occurrence rate for 4 Myr M0–M3 stars. We have also combined our results with those from previous studies to predict average rates for flares above 1 × 1035 erg for early M stars in nearby young associations.
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: Oxford University Press (OUP)
Date: 05-04-2022
Abstract: We analyse 829 481 stars from the Next Generation Transit Survey (NGTS) to extract variability periods. We utilize a generalization of the autocorrelation function (the G-ACF), which applies to irregularly s led time series data. We extract variability periods for 16 880 stars from late-A through to mid-M spectral types and periods between ∼0.1 and 130 d with no assumed variability model. We find variable signals associated with a number of astrophysical phenomena, including stellar rotation, pulsations, and multiple-star systems. The extracted variability periods are compared with stellar parameters taken from Gaia DR2, which allows us to identify distinct regions of variability in the Hertzsprung–Russell Diagram. We explore a s le of rotational main-sequence objects in period-colour space, in which we observe a dearth of rotation periods between 15 and 25 d. This ‘bi-modality’ was previously only seen in space-based data. We demonstrate that stars in sub-s les above and below the period gap appear to arise from a stellar population not significantly contaminated by excess multiple systems. We also observe a small population of long-period variable M-dwarfs, which highlight a departure from the predictions made by rotational evolution models fitted to solar-type main-sequence objects. The NGTS data spans a period and spectral type range that links previous rotation studies such as those using data from Kepler, K2, and MEarth.
Publisher: EDP Sciences
Date: 23-11-2010
Publisher: Oxford University Press (OUP)
Date: 22-11-2018
Publisher: EDP Sciences
Date: 2012
Publisher: Cambridge University Press (CUP)
Date: 12-2012
Publisher: EDP Sciences
Date: 28-03-2023
DOI: 10.1051/0004-6361/202245016
Abstract: Context. Measurements of the occultation of an exoplanet at visible wavelengths allow us to determine the reflective properties of a planetary atmosphere. The observed occultation depth can be translated into a geometric albedo. This in turn aids in characterising the structure and composition of an atmosphere by providing additional information on the wavelength-dependent reflective qualities of the aerosols in the atmosphere. Aims. Our aim is to provide a precise measurement of the geometric albedo of the gas giant HD 189733b by measuring the occultation depth in the broad optical bandpass of CHEOPS (350–1100 nm). Methods. We analysed 13 observations of the occultation of HD 189733b performed by CHEOPS utilising the Python package PyCHEOPS. The resulting occultation depth is then used to infer the geometric albedo accounting for the contribution of thermal emission from the planet. We also aid the analysis by refining the transit parameters combining observations made by the TESS and CHEOPS space telescopes. Results. We report the detection of an 24.7 ± 4.5 ppm occultation in the CHEOPS observations. This occultation depth corresponds to a geometric albedo of 0.076 ± 0.016. Our measurement is consistent with models assuming the atmosphere of the planet to be cloud-free at the scattering level and absorption in the CHEOPS band to be dominated by the resonant Na doublet. Taking into account previous optical-light occultation observations obtained with the Hubble Space Telescope, both measurements combined are consistent with a super-stellar Na elemental abundance in the dayside atmosphere of HD 189733b. We further constrain the planetary Bond albedo to between 0.013 and 0.42 at 3 σ confidence. Conclusions. We find that the reflective properties of the HD 189733b dayside atmosphere are consistent with a cloud-free atmosphere having a super-stellar metal content. When compared to an analogous CHEOPS measurement for HD 209458b, our data hint at a slightly lower geometric albedo for HD 189733b (0.076 ± 0.016) than for HD 209458b (0.096 ± 0.016), or a higher atmospheric Na content in the same modelling framework. While our constraint on the Bond albedo is consistent with previously published values, we note that the higher-end values of ~0.4, as derived previously from infrared phase curves, would also require peculiarly high reflectance in the infrared, which again would make it more difficult to disentangle reflected and emitted light in the total observed flux, and therefore to correctly account for reflected light in the interpretation of those phase curves. Lower reported values for the Bond albedos are less affected by this ambiguity.
Publisher: EDP Sciences
Date: 05-2012
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: EDP Sciences
Date: 07-2013
Publisher: Oxford University Press (OUP)
Date: 20-04-2019
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: American Astronomical Society
Date: 23-11-2011
Publisher: Oxford University Press (OUP)
Date: 03-10-2018
Publisher: Oxford University Press (OUP)
Date: 30-03-2021
Abstract: We report the discovery of four new hot Jupiters with the Next-Generation Transit Survey (NGTS). NGTS-15b, NGTS-16b, NGTS-17b, and NGTS-18b are short-period (P & 5 d) planets orbiting G-type main-sequence stars, with radii and masses between 1.10 and 1.30RJ and 0.41 and 0.76MJ, respectively. By considering the host star luminosities and the planets’ small orbital separations (0.039–0.052 au), we find that all four hot Jupiters are highly irradiated and therefore occupy a region of parameter space in which planetary inflation mechanisms become effective. Comparison with statistical studies and a consideration of the planets’ high incident fluxes reveal that NGTS-16b, NGTS-17b, and NGTS-18b are indeed likely inflated, although some disparities arise upon analysis with current Bayesian inflationary models. However, the underlying relationships that govern radius inflation remain poorly understood. We postulate that the inclusion of additional hyperparameters to describe latent factors such as heavy element fraction, as well as the addition of an updated catalogue of hot Jupiters, would refine inflationary models, thus furthering our understanding of the physical processes that give rise to inflated planets.
Publisher: Springer Science and Business Media LLC
Date: 14-09-2020
Publisher: Oxford University Press (OUP)
Date: 09-10-2018
Publisher: Oxford University Press (OUP)
Date: 20-09-2018
Publisher: EDP Sciences
Date: 28-08-2012
Publisher: Springer Science and Business Media LLC
Date: 12-2003
DOI: 10.1007/BF03216799
Publisher: Oxford University Press (OUP)
Date: 07-05-2018
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: Oxford University Press (OUP)
Date: 30-05-2022
Abstract: We present the discovery of TOI-2136 b, a sub-Neptune planet transiting a nearby M4.5V-type star every 7.85 d, identified through photometric measurements from the Transiting Exoplanet Survey Satellite (TESS) mission. The host star is located 33 pc away with a radius of R* = 0.34 ± 0.02 R⊙, a mass of $0.34\\pm 0.02 \\, \\mathrm{M}_{\\odot }$, and an effective temperature of 3342 ± 100 K. We estimate its stellar rotation period to be 75 ± 5 d based on archival long-term photometry. We confirm and characterize the planet based on a series of ground-based multiwavelength photometry, high-angular-resolution imaging observations, and precise radial velocities from Canada–France–Hawaii Telescope (CFHT)/SpectroPolarimètre InfraROUge (SPIRou). Our joint analysis reveals that the planet has a radius of 2.20 ± 0.17 R⊕ and a mass of 6.4 ± 2.4 M⊕. The mass and radius of TOI-2136 b are consistent with a broad range of compositions, from water-ice to gas-dominated worlds. TOI-2136 b falls close to the radius valley for M dwarfs predicted by thermally driven atmospheric mass-loss models, making it an interesting target for future studies of its interior structure and atmospheric properties.
Publisher: Oxford University Press (OUP)
Date: 24-04-2020
Abstract: We observed a transit of WASP-166 b using nine Next Generation Transit Survey (NGTS) telescopes simultaneously with the Transiting Exoplanet Survey Satellite (TESS) observations of the same transit. We achieved a photometric precision of 152 ppm per 30 min with the nine NGTS telescopes combined, matching the precision reached by TESS for the transit event around this bright (T = 8.87) star. The in idual NGTS light-curve noise is found to be dominated by scintillation noise and appears free from any time-correlated noise or any correlation between telescope systems. We fit the NGTS data for TC and Rp/R*. We find TC to be consistent to within 0.25σ of the result from the TESS data, and the difference between the TESS and NGTS measured Rp/R* values is 0.9σ. This experiment shows that multitelescope NGTS photometry can match the precision of TESS for bright stars, and will be a valuable tool in refining the radii and ephemerides for bright TESS candidates and planets. The transit timing achieved will also enable NGTS to measure significant transit timing variations in multiplanet systems.
Publisher: American Astronomical Society
Date: 07-05-2020
Publisher: Oxford University Press (OUP)
Date: 08-01-2020
Abstract: We determine rotation periods for 127 stars in the ∼115-Myr-old Blanco 1 open cluster using ∼200 d of photometric monitoring with the Next Generation Transit Survey. These stars span F5–M3 spectral types (1.2 M⊙ ≳ M ≳ 0.3 M⊙) and increase the number of known rotation periods in Blanco 1 by a factor of four. We determine rotation periods using three methods: Gaussian process (GP) regression, generalized autocorrelation function (G-ACF), and Lomb–Scargle (LS) periodogram, and find that the GP and G-ACF methods are more applicable to evolving spot modulation patterns. Between mid-F and mid-K spectral types, single stars follow a well-defined rotation sequence from ∼2 to 10 d, whereas stars in photometric multiple systems typically rotate faster. This may suggest that the presence of a moderate-to-high mass ratio companion inhibits angular momentum loss mechanisms during the early pre-main sequence, and this signature has not been erased at ∼100 Myr. The majority of mid-F to mid-K stars display evolving modulation patterns, whereas most M stars show stable modulation signals. This morphological change coincides with the shift from a well-defined rotation sequence (mid-F to mid-K stars) to a broad rotation period distribution (late-K and M stars). Finally, we compare our rotation results for Blanco 1 to the similarly aged Pleiades: the single-star populations in both clusters possess consistent rotation period distributions, which suggests that the angular momentum evolution of stars follows a well-defined pathway that is, at least for mid-F to mid-K stars, strongly imprinted by ∼100 Myr.
Publisher: EDP Sciences
Date: 09-2010
Publisher: Springer Science and Business Media LLC
Date: 13-10-2020
Publisher: Springer Science and Business Media LLC
Date: 06-11-2011
Publisher: EDP Sciences
Date: 02-12-2010
Publisher: EDP Sciences
Date: 11-2010
Publisher: EDP Sciences
Date: 06-06-2011
Publisher: EDP Sciences
Date: 09-2010
Publisher: EDP Sciences
Date: 28-02-2013
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: American Astronomical Society
Date: 07-2020
Abstract: We report the discovery of NGTS-11 b (=TOI-1847b), a transiting Saturn in a 35.46 day orbit around a mid K-type star ( = 5050 ± 80 K). We initially identified the system from a single-transit event in a TESS full-frame image light curve. Following 79 nights of photometric monitoring with an NGTS telescope, we observed a second full transit of NGTS-11 b approximately one year after the TESS single-transit event. The NGTS transit confirmed the parameters of the transit signal and restricted the orbital period to a set of 13 discrete periods. We combined our transit detections with precise radial-velocity measurements to determine the true orbital period and measure the mass of the planet. We find NGTS-11 b has a radius of , a mass of , and an equilibrium temperature of just K, making it one of the coolest known transiting gas giants. NGTS-11 b is the first exoplanet to be discovered after being initially identified as a TESS single-transit event, and its discovery highlights the power of intense photometric monitoring in recovering longer-period transiting exoplanets from single-transit events.
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: EDP Sciences
Date: 07-06-2011
Publisher: Cambridge University Press (CUP)
Date: 08-2015
DOI: 10.1017/S1743921316000867
Abstract: The IAU Working Group on Extrasolar Planets (WGESP) was created by the Executive Council as a Working Group of Division III. This decision took place in June 1999, that is only 7 years after the discovery of planets around the pulsar PSR B1257+12 and 4 years after the discovery of 51 Peg b. This working group was renewed for 3 years at the General Assembly in 2003 in Sydney, Australia. It was chaired by Alan Boss from Carnegie Institution of Washington. The WGESP members were Paul Butler, William Hubbard, Philip Ianna, Martin Kürster, Jack Lissauer, Michel Mayor, Karen Meech, Francois Mignard, Alan Penny, Andreas Quirrenbach, Jill Tarter, and Alfred Vidal-Madjar.
Publisher: Oxford University Press (OUP)
Date: 28-09-2020
Abstract: We report the discovery of the transiting exoplanet NGTS-12b by the Next Generation Transit Survey (NGTS). The host star, NGTS-12, is a V = 12.38 mag star with an effective temperature of Teff = 5690 ± 130 K. NGTS-12b orbits with a period of P = 7.53 d, making it the longest period planet discovered to date by the main NGTS survey. We verify the NGTS transit signal with data extracted from the Transiting Exoplanet Survey Satellite (TESS) full-frame images, and combining the photometry with radial velocity measurements from HARPS and FEROS we determine NGTS-12b to have a mass of 0.208 ± 0.022 MJ and a radius of 1.048 ± 0.032 RJ. NGTS-12b sits on the edge of the Neptunian desert when we take the stellar properties into account, highlighting the importance of considering both the planet and star when studying the desert. The long period of NGTS-12b combined with its low density of just 0.223 ± 0.029 g cm−3 make it an attractive target for atmospheric characterization through transmission spectroscopy with a Transmission Spectroscopy Metric of 89.4.
Publisher: EDP Sciences
Date: 08-2022
DOI: 10.1051/0004-6361/202244221
Abstract: Context. Stellar occultation is a powerful technique that allows the determination of some physical parameters of the occulting object. The result depends on the photometric accuracy, the temporal resolution, and the number of chords obtained. Space telescopes can achieve high photometric accuracy as they are not affected by atmospheric scintillation. Aims. Using ESA’s CHEOPS space telescope, we observed a stellar occultation by the transneptunian object (50000) Quaoar. We compare the obtained chord with previous occultations by this object and determine its astrometry with sub-milliarcsecond precision. Also, we determine upper limits to the presence of a global methane atmosphere on the occulting body. Methods. We predicted and observed a stellar occultation by Quaoar using the CHEOPS space telescope. We measured the occultation light curve from this dataset and determined the dis- and reappearance of the star behind the occulting body. Furthermore, a ground-based telescope in Australia was used to constrain Quaoar’s limb. Combined with results from previous works, these measurements allowed us to obtain a precise position of Quaoar at the occultation time. Results. We present the results obtained from the first stellar occultation by a transneptunian object using a space telescope orbiting Earth it was the occultation by Quaoar observed on 2020 June 11. We used the CHEOPS light curve to obtain a surface pressure upper limit of 85 nbar for the detection of a global methane atmosphere. Also, combining this observation with a ground-based observation, we fitted Quaoar’s limb to determine its astrometric position with an uncertainty below 1.0 mas. Conclusions. This observation is the first of its kind, and it shall be considered as a proof of concept of stellar occultation observations of transneptunian objects with space telescopes orbiting Earth. Moreover, it shows significant prospects for the James Webb Space Telescope.
Publisher: Oxford University Press (OUP)
Date: 20-09-2019
Abstract: We report the discovery and characterization of WASP-180Ab, a hot Jupiter confirmed by the detection of its Doppler shadow and by measuring its mass using radial velocities. We find the 0.9 ± 0.1 MJup, 1.24 ± 0.04 RJup planet to be in a misaligned, retrograde orbit around an F7 star with Teff = 6500 K and a moderate rotation speed of vsin i⋆ = 19.9 km s−1. The host star is the primary of a V = 10.7 binary, where a secondary separated by ∼5 arcsec (∼1200 au) contributes ∼ 30 per cent of the light. WASP-180Ab therefore adds to a small s le of transiting hot Jupiters known in binary systems. A 4.6-d modulation seen in the WASP data is likely to be the rotational modulation of the companion star, WASP-180B.
Publisher: American Astronomical Society
Date: 24-06-2015
Publisher: EDP Sciences
Date: 02-2012
Publisher: Oxford University Press (OUP)
Date: 30-09-2019
Abstract: We report on four new transiting hot Jupiters discovered by the WASP-South survey. WASP-178b transits a V = 9.9, A1V star with Teff = 9350 ± 150 K, the second-hottest transit host known. It has a highly bloated radius of 1.81 ± 0.09 RJup, in line with the known correlation between high irradiation and large size. With an estimated temperature of 2470 ± 60 K, the planet is one of the best targets for studying ultrahot Jupiters that is visible from the Southern hemisphere. The three host stars WASP-184, WASP-185, and WASP-192 are all post-main-sequence G0 stars of ages 4–8 Gyr. The larger stellar radii (1.3–1.7 M⊙) mean that the transits are relatively shallow (0.7–0.9 per cent) even though the planets have moderately inflated radii of 1.2–1.3 RJup. WASP-185b has an eccentric orbit (e = 0.24) and a relatively long orbital period of 9.4 d. A star that is 4.6 arcsec from WASP-185 and 4.4 mag fainter might be physically associated.
Publisher: Oxford University Press (OUP)
Date: 08-05-2020
Abstract: SPECULOOS-South, an observatory composed of four independent 1-m robotic telescopes, located at ESO Paranal, Chile, started scientific operation in 2019 January. This Southern hemisphere facility operates as part of the Search for Habitable Planets EClipsing ULtra-cOOl Stars (SPECULOOS), an international network of 1-m-class telescopes surveying for transiting terrestrial planets around the nearest and brightest ultracool dwarfs (UCDs). To automatically and efficiently process the observations of SPECULOOS-South, and to deal with the specialized photometric requirements of UCD targets, we present our automatic pipeline. This pipeline includes an algorithm for automated differential photometry and an extensive correction technique for the effects of telluric water vapour, using ground measurements of the precipitable water vapour. Observing very red targets in the near-infrared can result in photometric systematics in the differential light curves, related to the temporally-varying, wavelength-dependent opacity of the Earth’s atmosphere. These systematics are sufficient to affect the daily quality of the light curves, the longer time-scale variability study of our targets and even mimic transit-like signals. Here we present the implementation and impact of our water vapour correction method. Using the 179 nights and 98 targets observed in the I + z′ filter by SPECULOOS-South since 2019 January, we show the impressive photometric performance of the facility (with a median precision of ∼1.5 mmag for 30-min binning of the raw, non-detrended light curves) and assess its detection potential. We compare simultaneous observations with SPECULOOS-South and TESS, to show that we readily achieve high-precision, space-level photometry for bright, UCDs, highlighting SPECULOOS-South as the first facility of its kind.
Publisher: Oxford University Press (OUP)
Date: 23-08-2019
Abstract: We present the discovery of four new giant planets from the Wide Angle Search for Planets-South (WASP-South), three hot Jupiters and one bloated sub-Saturn mass planet: WASP-169b, WASP-171b, WASP-175b, and WASP-182b. Besides the discovery photometry from WASP-South we use radial velocity measurements from CORALIE and HARPS and follow-up photometry from EulerCam, TRAPPIST-North and -South, and SPECULOOS. WASP-169b is a low-density Jupiter ($M=0.561 \\pm 0.061\\,{M_{\\rm Jup}},\\ R=1.304^{+0.150}_{-0.073}\\,{R_{\\rm Jup}}$) orbiting a V = 12.17 F8 subgiant in a 5.611 d orbit. WASP-171b is a typical hot Jupiter ($M=1.084 \\pm 0.094\\,{M_{\\rm Jup}},\\ R=0.98^{+0.07}_{-0.04}\\,{R_{\\rm Jup}}$, P = 3.82 d) around a V = 13.05 G0 star. We find a linear drift in the radial velocities of WASP-171 spanning 3.5 yr, indicating the possibility of an additional outer planet or stellar companion. WASP-175b is an inflated hot Jupiter (M = 0.99 ± 0.13 MJup, R = 1.208 ± 0.081 RJup, P = 3.07 d) around a V = 12.04 F7 star, which possibly is part of a binary system with a star 7.9 arcsec away. WASP-182b is a bloated sub-Saturn mass planet (M = 0.148 ± 0.011 MJup, R = 0.850 ± 0.030 RJup) around a metal-rich V = 11.98 G5 star ([Fe/H] = 0.27 ± 0.11). With an orbital period of P = 3.377 d, it sits right in the apex of the sub-Jovian desert, bordering the upper and lower edge of the desert in both the mass–period and radius–period plane. WASP-169b, WASP-175b, and WASP-182b are promising targets for atmospheric characterization through transmission spectroscopy, with expected transmission signals of 121, 150, and 264 ppm, respectively.
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Publisher: EDP Sciences
Date: 09-2010
Publisher: EDP Sciences
Date: 08-03-2011
Publisher: American Astronomical Society
Date: 14-03-2019
Publisher: Oxford University Press (OUP)
Date: 18-05-2018
Publisher: EDP Sciences
Date: 2012
Publisher: EDP Sciences
Date: 05-2019
DOI: 10.1051/0004-6361/201935356
Abstract: Context. Since 1998, a planet-search around main sequence stars within 50 pc in the southern hemisphere has been underway with the CORALIE spectrograph at La Silla Observatory. Aims. With an observing time span of more than 20 yr, the CORALIE survey is able to detect long-term trends in data with masses and separations large enough to select ideal targets for direct imaging. Detecting these giant companion candidates will allow us to start bridging the gap between radial-velocity-detected exoplanets and directly imaged planets and brown dwarfs. Methods. Long-term precise Doppler measurements with the CORALIE spectrograph reveal radial-velocity signatures of massive planetary companions and brown dwarfs on long-period orbits. Results. In this paper, we report the discovery of new companions orbiting HD 181234, HD 13724, HD 25015, HD 92987 and HD 50499. We also report updated orbital parameters for HD 50499b, HD 92788b and HD 98649b. In addition, we confirm the recent detection of HD 92788c. The newly reported companions span a period range of 15.6–40.4 yr and a mass domain of 2.93–26.77 M Jup , the latter of which straddles the nominal boundary between planets and brown dwarfs. Conclusions. We report the detection of five new companions and updated parameters of four known extrasolar planets. We identify at least some of these companions to be promising candidates for imaging and further characterisation.
Publisher: Oxford University Press (OUP)
Date: 10-07-2019
Abstract: We report the discovery of WASP-166b, a super-Neptune planet with a mass of 0.1 MJup (1.9 MNep) and a bloated radius of 0.63 RJup. It transits a V = 9.36, F9V star in a 5.44-d orbit that is aligned with the stellar rotation axis (sky-projected obliquity angle λ = 3 ± 5 deg). Variations in the radial-velocity measurements are likely the result of magnetic activity over a 12-d stellar rotation period. WASP-166b appears to be a rare object within the ‘Neptune desert’.
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
No related grants have been discovered for Didier Queloz.