| 1. |
- Bourrier, V., et al.
(author)
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A CHEOPS-enhanced view of the HD 3167 system
- 2022
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 668
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Journal article (peer-reviewed)abstract
- Much remains to be understood about the nature of exoplanets smaller than Neptune, most of which have been discovered in compact multi-planet systems. With its inner ultra-short period planet b aligned with the star and two larger outer planets d-c on polar orbits, the multi-planet system HD 3167 features a peculiar architecture and offers the possibility to investigate both dynamical and atmospheric evolution processes. To this purpose we combined multiple datasets of transit photometry and radial velocimetry (RV) to revise the properties of the system and inform models of its planets. This effort was spearheaded by CHEOPS observations of HD 3167b, which appear inconsistent with a purely rocky composition despite its extreme irradiation. Overall the precision on the planetary orbital periods are improved by an order of magnitude, and the uncertainties on the densities of the transiting planets b and c are decreased by a factor of 3. Internal structure and atmospheric simulations draw a contrasting picture between HD 3167d, likely a rocky super-Earth that lost its atmosphere through photo-evaporation, and HD 3167c, a mini-Neptune that kept a substantial primordial gaseous envelope. We detect a fourth, more massive planet on a larger orbit, likely coplanar with HD 3167d-c. Dynamical simulations indeed show that the outer planetary system d-c-e was tilted, as a whole, early in the system history, when HD 3167b was still dominated by the star influence and maintained its aligned orbit. RV data and direct imaging rule out that the companion that could be responsible for the present-day architecture is still bound to the HD 3167 system. Similar global studies of multi-planet systems will tell how many share the peculiar properties of the HD 3167 system, which remains a target of choice for follow-up observations and simulations.
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| 2. |
- Leleu, A., et al.
(author)
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Six transiting planets and a chain of Laplace resonances in TOI-178
- 2021
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 649
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Journal article (peer-reviewed)abstract
- Determining the architecture of multi-planetary systems is one of the cornerstones of understanding planet formation and evolution. Resonant systems are especially important as the fragility of their orbital configuration ensures that no significant scattering or collisional event has taken place since the earliest formation phase when the parent protoplanetary disc was still present. In this context, TOI-178 has been the subject of particular attention since the first TESS observations hinted at the possible presence of a near 2:3:3 resonant chain. Here we report the results of observations from CHEOPS, ESPRESSO, NGTS, and SPECULOOS with the aim of deciphering the peculiar orbital architecture of the system. We show that TOI-178 harbours at least six planets in the super-Earth to mini-Neptune regimes, with radii ranging from 1.152 to 2.87 Earth radii and periods of 1.91, 3.24, 6.56, 9.96, 15.23, and 20.71 days. All planets but the innermost one form a 2:4:6:9:12 chain of Laplace resonances, and the planetary densities show important variations from planet to planet, jumping from 1.02 to 0.177 times the Earth's density between planets c and d. Using Bayesian interior structure retrieval models, we show that the amount of gas in the planets does not vary in a monotonous way, contrary to what one would expect from simple formation and evolution models and unlike other known systems in a chain of Laplace resonances. The brightness of TOI-178 (H = 8.76 mag, J = 9.37 mag, V = 11.95 mag) allows for a precise characterisation of its orbital architecture as well as of the physical nature of the six presently known transiting planets it harbours. The peculiar orbital configuration and the diversity in average density among the planets in the system will enable the study of interior planetary structures and atmospheric evolution, providing important clues on the formation of super-Earths and mini-Neptunes. -0.070 -0.13 -0.23 -0.061 +0.073 +0.14 +0.28 +0.055
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| 3. |
- Szabo, Gy M., et al.
(author)
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Transit timing variations of AU Microscopii b and c*
- 2022
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 659
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Journal article (peer-reviewed)abstract
- Here we report large-amplitude transit timing variations (TTVs) for AU Microcopii b and c as detected in combined TESS (2018, 2020) and CHEOPS (2020, 2021) transit observations. AU Mic is a young planetary system with a debris disk and two transiting warm Neptunes. A TTV on the order of several minutes was previously reported for AU Mic b, which was suggested to be an outcome of mutual perturbations between the planets in the system. In 2021, we observed AU Mic b (five transits) and c (three transits) with the CHEOPS space telescope to follow-up the TTV of AU Mic b and possibly detect a TTV for AU Mic c. When analyzing TESS and CHEOPS 2020-2021 measurements together, we find that a prominent TTV emerges with a full span of >= 23 min between the two TTV extrema. Assuming that the period change results from a periodic process -such as mutual perturbations- we demonstrate that the times of transits in the summer of 2022 are expected to be 30-85 min later than predicted by the available linear ephemeris.
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| 4. |
- Alonso, R., et al.
(author)
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No random transits in CHEOPS observations of HD 139139 *,**
- 2023
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In: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 680
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Journal article (peer-reviewed)abstract
- Context . The star HD 139139 (a.k.a. ‘the Random Transiter’) is a star that exhibited enigmatic transit-like features with no apparent periodicity in K2 data. The shallow depth of the events (-200 ppm - equivalent to transiting objects with radii of -1.5 R⊕ in front of a Sun-like star) and their non-periodicity constitute a challenge for the photometric follow-up of this star. Aims . The goal of this study is to confirm with independent measurements the presence of shallow, non-periodic transit-like features on this object. Methods . We performed observations with CHEOPS for a total accumulated time of 12.75 days, distributed in visits of roughly 20 h in two observing campaigns in years 2021 and 2022. The precision of the data is sufficient to detect 150 ppm features with durations longer than 1.5 h. We used the duration and times of the events seen in the K2 curve to estimate how many events should have been detected in our campaigns, under the assumption that their behaviour during the CHEOPS observations would be the same as in the K2 data of 2017. Results . We do not detect events with depths larger than 150 ppm in our data set. If the frequency, depth, and duration of the events were the same as in the K2 campaign, we estimate the probability of having missed all events due to our limited observing window would be 4.8%. Conclusions . We suggest three different scenarios to explain our results: 1) Our observing window was not long enough, and the events were missed with the estimated 4.8% probability. 2) The events recorded in the K2 observations were time critical, and the mechanism producing them was either not active in the 2021 and 2022 campaigns or created shallower events under our detectability level. 3) The enigmatic events in the K2 data are the result of an unidentified and infrequent instrumental noise in the original data set or its data treatment.
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| 5. |
- Bonnard, Å, et al.
(author)
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Vestibular Loss in Children Affected by LVAS and IP2 Malformation and Operated with Cochlear Implant
- 2023
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In: Audiology research. - : MDPI AG. - 2039-4330 .- 2039-4349. ; 13:1, s. 130-142
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Journal article (peer-reviewed)abstract
- This is a single center cohort study regarding the prevalence of vestibular loss in hearing impaired children affected by large vestibular aqueduct syndrome (LVAS) with incomplete cochlear partition malformation type II (IP2), fitted with cochlear implant (CI). Twenty-seven children received CI operations at 0.4–13 years on one or both ears and tested for vestibular loss with head impulse test, video head impulse test, mini ice-water test and cervical VEMP. Vestibular loss was found in 19% of operated ears and in 13.9% of non-operated ears. The difference was not statistically significant and was not significantly modified by age at implantation, age at testing, sex, presence of SLC26A4 gene mutation or bilaterality. However, the presence of anatomic anomalies at the level of the vestibulum or semicircular canals was significantly associated with a higher incidence of vestibular loss in CI operated children but not in those non-operated. No other factors, such as the surgical access, the electrode type, the presence of Gusher perioperatively, or post-operative vertigo modified significantly the prevalence of vestibular loss. In conclusion, LVAS/IP2 appears to be the major determinant of vestibular loss in these children, with a less obvious impact of CI, excluding the cases with vestibulum/canal anomalies: this group might have a higher risk for vestibular loss after CI surgery.
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