| 1. |
- Hawthorn, F., et al.
(författare)
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TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 520:3, s. 3649-3668
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Tidskriftsartikel (refereegranskat)abstract
- 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 0.68 ± 0.05 M and a radius of 0.67 ± 0.01 R. We obtain photometric follow-up observations with a variety of facilities, and we use these data sets to determine that the inner planet, TOI-836 b, is a 1.70 ± 0.07 R super-Earth in a 3.82-d orbit, placing it directly within the so-called ‘radius valley’. The outer planet, TOI-836 c, is a 2.59 ± 0.09 R mini-Neptune in an 8.60-d orbit. Radial velocity measurements reveal that TOI-836 b has a mass of 4.5 ± 0.9 M, while TOI-836 c has a mass of 9.6 ± 2.6 M. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 min for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet.
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| 2. |
- Lendl, M., et al.
(författare)
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The hot dayside and asymmetric transit of WASP-189 b seen by CHEOPS
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 643
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Tidskriftsartikel (refereegranskat)abstract
- The CHEOPS space mission dedicated to exoplanet follow-up was launched in December 2019, equipped with the capacity to perform photometric measurements at the 20 ppm level. As CHEOPS carries out its observations in a broad optical passband, it can provide insights into the reflected light from exoplanets and constrain the short-wavelength thermal emission for the hottest of planets by observing occultations and phase curves. Here, we report the first CHEOPS observation of an occultation, namely, that of the hot Jupiter WASP-189 b, a MP ≈ 2MJ planet orbiting an A-type star. We detected the occultation of WASP-189 b at high significance in individual measurements and derived an occultation depth of dF = 87.9 ± 4.3 ppm based on four occultations. We compared these measurements to model predictions and we find that they are consistent with an unreflective atmosphere heated to a temperature of 3435 ± 27 K, when assuming inefficient heat redistribution. Furthermore, we present two transits of WASP-189 b observed by CHEOPS. These transits have an asymmetric shape that we attribute to gravity darkening of the host star caused by its high rotation rate. We used these measurements to refine the planetary parameters, finding a ~25% deeper transit compared to the discovery paper and updating the radius of WASP-189 b to 1.619 ± 0.021RJ. We further measured the projected orbital obliquity to be λ = 86.4-4.4+2.9°, a value that is in good agreement with a previous measurement from spectroscopic observations, and derived a true obliquity of ψ = 85.4 ± 4.3°. Finally, we provide reference values for the photometric precision attained by the CHEOPS satellite: for the V = 6.6 mag star, and using a 1-h binning, we obtain a residual RMS between 10 and 17 ppm on the individual light curves, and 5.7 ppm when combining the four visits.
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| 3. |
- Meier Valdes, E., et al.
(författare)
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Investigating the visible phase-curve variability of 55 Cnc e
- 2023
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 677
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Tidskriftsartikel (refereegranskat)abstract
- Context. 55 Cnc e is an ultra-short period super-Earth transiting a Sun-like star. Previous observations in the optical range detected a time-variable flux modulation that is phased with the planetary orbital period, whose amplitude is too large to be explained by reflected light and thermal emission alone. Aims. The goal of the study is to investigate the origin of the variability and timescale of the phase-curve modulation in 55 Cnc e. To this end, we used the CHaracterising ExOPlanet Satellite (CHEOPS), whose exquisite photometric precision provides an opportunity to characterise minute changes in the phase curve from one orbit to the next. Methods. CHEOPS observed 29 individual visits of 55 Cnc e between March 2020 and February 2022. Based on these observations, we investigated the different processes that could be at the origin of the observed modulation. In particular, we built a toy model to assess whether a circumstellar torus of dust driven by radiation pressure and gravity might match the observed flux variability timescale. Results. We find that the phase-curve amplitude and peak offset of 55 Cnc e do vary between visits. The sublimation timescales of selected dust species reveal that silicates expected in an Earth-like mantle would not survive long enough to explain the observed phase-curve modulation. We find that silicon carbide, quartz, and graphite are plausible candidates for the circumstellar torus composition because their sublimation timescales are long. Conclusions. The extensive CHEOPS observations confirm that the phase-curve amplitude and offset vary in time. We find that dust could provide the grey opacity source required to match the observations. However, the data at hand do not provide evidence that circumstellar material with a variable grain mass per unit area causes the observed variability. Future observations with the James Webb Space Telescope (JWST) promise exciting insights into this iconic super-Earth.
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| 4. |
- Prost, Stefan, et al.
(författare)
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Comparative analyses identify genomic features potentially involved in the evolution of birds-of-paradise
- 2019
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Ingår i: GigaScience. - : OXFORD UNIV PRESS. - 2047-217X. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- The diverse array of phenotypes and courtship displays exhibited by birds-of-paradise have long fascinated scientists and nonscientists alike. Remarkably, almost nothing is known about the genomics of this iconic radiation. There are 41 species in 16 genera currently recognized within the birds-of-paradise family (Paradisaeidae), most of which are endemic to the island of New Guinea. In this study, we sequenced genomes of representatives from all five major clades within this family to characterize genomic changes that may have played a role in the evolution of the group's extensive phenotypic diversity. We found genes important for coloration, morphology, and feather and eye development to be under positive selection. In birds-of-paradise with complex lekking systems and strong sexual dimorphism, the core birds-of-paradise, we found Gene Ontology categories for "startle response" and "olfactory receptor activity" to be enriched among the gene families expanding significantly faster compared to the other birds in our study. Furthermore, we found novel families of retrovirus-like retrotransposons active in all three de novo genomes since the early diversification of the birds-of-paradise group, which might have played a role in the evolution of this fascinating group of birds.
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| 5. |
- Blom, Mozes P. K., et al.
(författare)
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Hybridization in birds-of-paradise : Widespread ancestral gene flow despite strong sexual selection in a lek-mating system
- 2024
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Ingår i: iScience. - : Cell Press. - 2589-0042. ; 27:7
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Tidskriftsartikel (refereegranskat)abstract
- Sexual selection can directly contribute to reproductive isolation and is an important mechanism that can lead to speciation. Lek-mating is one of the most extreme forms of sexual selection, but surprisingly does not seem to preclude occasional hybridization in nature. However, hybridization among lekking species may still be trivial if selection against offspring with intermediate phenotypes prohibits introgression. Here we investigate this further by sequencing the genomes of nearly all bird-of-paradise (Paradisaeidae) species and 10 museum specimens of putative hybrid origin. We find that intergeneric hybridization indeed still takes place despite extreme differentiation in form, plumage, and behavior. In parallel, the genomes of contemporary species contain widespread signatures of past introgression, demonstrating that hybridization has repeatedly resulted in shared genetic variation despite strong sexual isolation. Our study raises important questions about extrinsic factors that modulate hybridization probability and the evolutionary consequences of introgressive hybridization between lekking species.
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| 6. |
- Oliveros, Carl H., et al.
(författare)
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Earth history and the passerine superradiation
- 2019
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 116:16, s. 7916-7925
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Tidskriftsartikel (refereegranskat)abstract
- Avian diversification has been influenced by global climate change, plate tectonic movements, and mass extinction events. However, the impact of these factors on the diversification of the hyper-diverse perching birds (passerines) is unclear because family level relationships are unresolved and the timing of splitting events among lineages is uncertain. We analyzed DNA data from 4,060 nuclear loci and 137 passerine families using concatenation and coalescent approaches to infer a comprehensive phylogenetic hypothesis that clarifies relationships among all passerine families. Then, we calibrated this phylogeny using 13 fossils to examine the effects of different events in Earth history on the timing and rate of passerine diversification. Our analyses reconcile passerine diversification with the fossil and geological records; suggest that passerines originated on the Australian landmass ∼47 Ma; and show that subsequent dispersal and diversification of passerines was affected by a number of climatological and geological events, such as Oligocene glaciation and inundation of the New Zealand landmass. Although passerine diversification rates fluctuated throughout the Cenozoic, we find no link between the rate of passerine diversification and Cenozoic global temperature, and our analyses show that the increases in passerine diversification rate we observe are disconnected from the colonization of new continents. Taken together, these results suggest more complex mechanisms than temperature change or ecological opportunity have controlled macroscale patterns of passerine speciation.
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| 7. |
- Peona, Valentina, et al.
(författare)
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The hidden structural variability in avian genomes
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Structural variants (SVs) are DNA mutations that can have relevant effects at the micro- and macro-evolutionary scales. The detection of SVs is largely limited by the type and quality of sequencing technologies adopted, therefore genetic variability linked to SVs may remain undiscovered especially in complex repetitive regions. In this study, we used a combination of long-read and linked-read genome assemblies to explore the occurrence of insertions and deletions across the chromosomes of 14 species birds-of-paradise and two species of estrildid finches. The species sampling encompasses all genera of birds-of-paradise, allowing comparisons between individuals of the same species, genus, and family. Interestingly, we found the highest densities of SVs to be located on the microchromosomes and on the female-specific W chromosome. Genome assemblies of multiple individuals from the same species allowed us to compare the levels of genetic variability linked to SVs and single nucleotide polymorphisms (SNPs) on the W and other chromosomes. Our results demonstrate that the avian W chromosome harbours more genetic variability than previously thought and that its structure is shaped by the continuous accumulation and turnover of transposable element insertions, especially endogenous retroviruses.
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