| 1. |
|
|
| 2. |
- Barausse, Enrico, et al.
(författare)
-
Prospects for fundamental physics with LISA
- 2020
-
Ingår i: General Relativity and Gravitation. - : SPRINGER/PLENUM PUBLISHERS. - 0001-7701 .- 1572-9532. ; 52:8
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, which is of programmatic rather than quantitative nature, we aim to further delineate and sharpen the future potential of the LISA mission in the area of fundamental physics. Given the very broad range of topics that might be relevant to LISA,we present here a sample of what we view as particularly promising fundamental physics directions. We organize these directions through a "science-first" approach that allows us to classify how LISA data can inform theoretical physics in a variety of areas. For each of these theoretical physics classes, we identify the sources that are currently expected to provide the principal contribution to our knowledge, and the areas that need further development. The classification presented here should not be thought of as cast in stone, but rather as a fluid framework that is amenable to change with the flow of new insights in theoretical physics.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Sebastian, D., et al.
(författare)
-
The EBLM project - IX. Five fully convective M-dwarfs, precisely measured with CHEOPS and TESS light curves
- 2023
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 519:3, s. 3546-3563
-
Tidskriftsartikel (refereegranskat)abstract
- Eclipsing binaries are important benchmark objects to test and calibrate stellar structure and evolution models. This is especially true for binaries with a fully convective M-dwarf component for which direct measurements of these stars' masses and radii are difficult using other techniques. Within the potential of M-dwarfs to be exoplanet host stars, the accuracy of theoretical predictions of their radius and effective temperature as a function of their mass is an active topic of discussion. Not only the parameters of transiting exoplanets but also the success of future atmospheric characterization relies on accurate theoretical predictions. We present the analysis of five eclipsing binaries with low-mass stellar companions out of a subsample of 23, for which we obtained ultra-high-precision light curves using the CHEOPS satellite. The observation of their primary and secondary eclipses are combined with spectroscopic measurements to precisely model the primary parameters and derive the M-dwarfs mass, radius, surface gravity, and effective temperature estimates using the PYCHEOPS data analysis software. Combining these results to the same set of parameters derived from TESS light curves, we find very good agreement (better than 1 percent for radius and better than 0.2 percent for surface gravity). We also analyse the importance of precise orbits from radial velocity measurements and find them to be crucial to derive M-dwarf radii in a regime below 5 percent accuracy. These results add five valuable data points to the mass-radius diagram of fully convective M-dwarfs.
|
|
| 6. |
- Alonso, R., et al.
(författare)
-
No random transits in CHEOPS observations of HD 139139 *,**
- 2023
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 680
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 7. |
- Collins, C. G., et al.
(författare)
-
Experimental warming differentially affects vegetative and reproductive phenology of tundra plants
- 2021
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- Rapid climate warming is altering Arctic and alpine tundra ecosystem structure and function, including shifts in plant phenology. While the advancement of green up and flowering are well-documented, it remains unclear whether all phenophases, particularly those later in the season, will shift in unison or respond divergently to warming. Here, we present the largest synthesis to our knowledge of experimental warming effects on tundra plant phenology from the International Tundra Experiment. We examine the effect of warming on a suite of season-wide plant phenophases. Results challenge the expectation that all phenophases will advance in unison to warming. Instead, we find that experimental warming caused: (1) larger phenological shifts in reproductive versus vegetative phenophases and (2) advanced reproductive phenophases and green up but delayed leaf senescence which translated to a lengthening of the growing season by approximately 3%. Patterns were consistent across sites, plant species and over time. The advancement of reproductive seasons and lengthening of growing seasons may have significant consequences for trophic interactions and ecosystem function across the tundra. It is unclear whether climate driven phenological shifts of tundra plants are consistent across the plant growing season. Here the authors analyse data from a network of field warming experiments in Arctic and alpine tundra, finding that warming differentially affects the timing and duration of reproductive and vegetative phenology.
|
|
| 8. |
- Krenn, A., et al.
(författare)
-
The geometric albedo of the hot Jupiter HD 189733b measured with CHEOPS
- 2023
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 672
-
Tidskriftsartikel (refereegranskat)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 3σconfidence. 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.
|
|
| 9. |
- Pagano, I., et al.
(författare)
-
Constraining the reflective properties of WASP-178 b using CHEOPS photometry
- 2024
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 682
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Multiwavelength photometry of the secondary eclipses of extrasolar planets is able to disentangle the reflected and thermally emitted light radiated from the planetary dayside. Based on this, we can measure the planetary geometric albedo Ag, which is an indicator of the presence of clouds in the atmosphere, and the recirculation efficiency ϵ, which quantifies the energy transport within the atmosphere. Aims. We measure Ag and ϵ for the planet WASP-178 b, a highly irradiated giant planet with an estimated equilibrium temperature of 2450 K. Methods. We analyzed archival spectra and the light curves collected by CHEOPS and TESS to characterize the host WASP-178, refine the ephemeris of the system, and measure the eclipse depth in the passbands of the two telescopes. Results. We measured a marginally significant eclipse depth of 70 ± 40 ppm in the TESS passband, and a statistically significant depth of 70 ± 20 ppm in the CHEOPS passband. Conclusions. Combining the eclipse-depth measurement in the CHEOPS (λeff = 6300 Å) and TESS (λeff = 8000 Å) passbands, we constrained the dayside brightness temperature of WASP-178 b in the 2250-2800 K interval. The geometric albedo 0.1< Ag<0.35 generally supports the picture that giant planets are poorly reflective, while the recirculation efficiency ϵ >0.7 makes WASP-178 b an interesting laboratory for testing the current heat-recirculation models.
|
|
| 10. |
- Patel, Jayshil Ashokkumar, et al.
(författare)
-
CHEOPS and TESS view of the ultra-short-period super-Earth TOI-561 b
- 2023
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 679
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Ultra-short-period planets (USPs) are a unique class of super-Earths with an orbital period of less than a day, and hence they are subject to intense radiation from their host star. These planets cannot retain a primordial H/He atmosphere, and most of them are indeed consistent with being bare rocky cores. A few USPs, however, show evidence for a heavyweight envelope, which could be a water layer resilient to evaporation or a secondary metal-rich atmosphere sustained by outgassing of the molten volcanic surface. Much thus remains to be learned about the nature and formation of USPs. Aims. The prime goal of the present work is to refine the bulk planetary properties of the recently discovered TOI-561 b through the study of its transits and occultations. This is crucial in order to understand the internal structure of this USP and to assess the presence of an atmosphere. Methods. We obtained ultra-precise transit photometry of TOI-561 b with CHEOPS, and performed a joint analysis of these data along with three archival visits from CHEOPS and four TESS sectors. Results. Our analysis of TOI-561 b transit photometry put strong constraints on its properties. In particular, we restrict the uncertainties on the planetary radius at similar to 2% retrieving R-p = 1.42 +/- 0.02 R-circle plus. This result informs our internal structure modelling of the planet, which shows that the observations are consistent with a negligible H/He atmosphere; however, other lighter materials are required, in addition to a pure iron core and a silicate mantle, to explain the observed density. We find that this can be explained by the inclusion of a water layer in our model. Additionally, we ran a grid of forward models with a water-enriched atmosphere to explain the transit radius. We searched for variability in the measured R-p/R-star over time, which could trace changes in the structure of the planetary envelope. However, no temporal variations are recovered within the present data precision. In addition to the transit event, we tentatively detect an occultation signal in the TESS data with an eclipse depth L = 27.40(-11.35)(+10.87) ppm. We use models of outgassed atmospheres from the literature to explain this eclipse signal. We find that the thermal emission from the planet can mostly explain the observation. Based on this, we predict that near- to mid-infrared observations with the James Webb Space Telescope should be able to detect silicate species in the atmosphere of the planet. This could also reveal important clues about the planetary interior and help disentangle planet formation and evolution models.
|
|
