| 11. |
- Bourrier, V., et al.
(författare)
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A CHEOPS-enhanced view of the HD 3167 system
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 668
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Tidskriftsartikel (refereegranskat)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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| 12. |
- Benmahi, B., et al.
(författare)
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Monitoring of the evolution of H2O vapor in the stratosphere of Jupiter over an 18-yr period with the Odin space telescope
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 641
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Tidskriftsartikel (refereegranskat)abstract
- Context. The comet Shoemaker-Levy 9 impacted Jupiter in July 1994, leaving its stratosphere with several new species, with water vapor (H2O) among them. Aims. With the aid of a photochemical model, H2O can be used as a dynamical tracer in the Jovian stratosphere. In this paper, we aim to constrain the vertical eddy diffusion (Kzz) at levels where H2O is present. Methods. We monitored the H2O disk-averaged emission at 556.936 GHz with the space telescope between 2002 and 2019, covering nearly two decades. We analyzed the data with a combination of 1D photochemical and radiative transfer models to constrain the vertical eddy diffusion in the stratosphere of Jupiter. Results. Odin observations show us that the emission of H2O has an almost linear decrease of about 40% between 2002 and 2019. We can only reproduce our time series if we increase the magnitude of Kzz in the pressure range where H2O diffuses downward from 2002 to 2019, that is, from ~0.2 mbar to ~5 mbar. However, this modified Kzz is incompatible with hydrocarbon observations. We find that even if an allowance is made for the initially large abundances of H2O and CO at the impact latitudes, the photochemical conversion of H2O to CO2 is not sufficient to explain the progressive decline of the H2O line emission, which is suggestive of additional loss mechanisms. Conclusions. The Kzz we derived from the Odin observations of H2O can only be viewed as an upper limit in the ~0.2 mbar to ~5 mbar pressure range. The incompatibility between the interpretations made from H2O and hydrocarbon observations probably results from 1D modeling limitations. Meridional variability of H2O, most probably at auroral latitudes, would need to be assessed and compared with that of hydrocarbons to quantify the role of auroral chemistry in the temporal evolution of the H2O abundance since the SL9 impacts. Modeling the temporal evolution of SL9 species with a 2D model would naturally be the next step in this area of study.
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| 13. |
- Posch, Josefina
(författare)
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EP9 Starlight Reserves
- 2023
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Ingår i: Göteborgs Botaniska Trädgård, GIBCA Extended, 2023-08-19.
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- The sculpture EP9 Starlight Reserves was installed in Amerikadammen in Göteborgs Botaniska Trädgård and part of GIBCA Extended 2023. This work is situated in the expanded field of sculpture, where the negotiation with a specific situation plays a central role in material investigations of environmental and sustainability concerns. The shape and title of the sculpture derive from the container of old batteries, "Exposed Pallet 9," which the International Space Station launched into space in 2021 to circulate around the Earth for 2-4 years before entering the Earth's atmosphere and hopefully burn up. [1] Commercial interests, colonization, and tourism led by rich nations and private companies contribute to the increase of space debris. The main inquiry of this research project is how artistic work, through visualization in sculptural form, can draw attention to scientific observations and advocacy in establishing international environmental space law concerning space debris. By using recycled plastic from electronic scrap for the large-scale IRBAM printing of the sculpture, the work highlights the potential for sustainable and ephemeral materials in sculptural production to promote environmental awareness and question the validity of the standard requirement for "permanence" in public sculpture. 3D printing in collaboration with Samuel Johansson and Woodrow Wiest RISE – AM center in Mölndal, Sweden with in-kind funding. Supported by Göteborgs Stad Kultur och Göteborgs Botaniska Trädgård. [1] Mike Wall, “Space station tosses 2.9-ton hunk of space junk overboard. It will stay in orbit for years.”, space.com, accessed January 3, 2024, https://www.space.com/space-station-jettisons-huge-space-junk-pallet
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| 14. |
- Jones, K., et al.
(författare)
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The stable climate of KELT-9b
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
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Tidskriftsartikel (refereegranskat)abstract
- Even among the most irradiated gas giants, so-called ultra-hot Jupiters, KELT-9b stands out as the hottest planet thus far discovered with a dayside temperature of over 4500 K. At these extreme irradiation levels, we expect an increase in heat redistribution efficiency and a low Bond albedo owed to an extended atmosphere with molecular hydrogen dissociation occurring on the planetary dayside. We present new photometric observations of the KELT-9 system throughout 4 full orbits and 9 separate occultations obtained by the 30 cm space telescope CHEOPS. The CHEOPS bandpass, located at optical wavelengths, captures the peak of the thermal emission spectrum of KELT-9b. In this work we simultaneously analyse CHEOPS phase curves along with public phase curves from TESS and Spitzer to infer joint constraints on the phase curve variation, gravity-darkened transits, and occultation depth in three bandpasses, as well as derive 2D temperature maps of the atmosphere at three different depths. We find a day-night heat redistribution efficiency of similar to 0.3 which confirms expectations of enhanced energy transfer to the planetary nightside due to dissociation and recombination of molecular hydrogen. We also calculate a Bond albedo consistent with zero. We find no evidence of variability of the brightness temperature of the planet, excluding variability greater than 1% (1 sigma).
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| 15. |
- 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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| 16. |
- Belete, A. Bewketu, et al.
(författare)
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Molecular gas kinematics in the nuclear region of nearby Seyfert galaxies with ALMA
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 654
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Tidskriftsartikel (refereegranskat)abstract
- Context. The study of the distribution, morphology, and kinematics of cold molecular gas in the nuclear and circumnuclear regions of active galactic nuclei (AGNs) helps to characterise and hence to quantify the impact of the AGNs on the host galaxy over its lifetime. Aims. We present the analysis of the molecular gas in the nuclear regions of three Seyfert galaxies, NGC 4968, NGC 4845, and MCG-06-30-15, using Atacama Large sub-Millimetre Array (ALMA) observations of the CO(2-1) emission line. The aim is to determine the kinematics of the gas in the central (∼1 kpc) region and thereby to probe nuclear fueling and feedback of AGNs. Methods. We used two different softwares, namely the 3D-Based Analysis of Rotating Object via Line Observations and DiskFit, to model the kinematics of the gas in the molecular disc, and thereby to determine the gas rotation and any kinematical perturbations. Results. Circular motions dominate the kinematics of the molecular gas in the central discs, mainly in NGC 4845 and MCG-06-30-15; however there is clear evidence of non-circular motions in the central (∼1 kpc) region of NGC 4845 and NGC 4968. The strongest non-circular motion is detected in the inner disc of NGC 4968, mainly along the minor kinematic axis, with a velocity ∼115 km s-1. Of all DiskFit models, the bisymmetric model is found to give the best fit for NGC 4968 and NGC 4845, indicating that the observed non-circular motions in the inner disc of these galaxies could result from the nuclear barred structure, where the gas streams in elliptical orbits aligned along the bar. If the dynamics of NGC 4968 is modelled as a corotation pattern just outside of the bar, the bar pattern speed becomes ωb = 52 km s-1 kpc-1; the corotation is set at 3.5 kpc; and the inner Lindblad resonance (ILR) ring is R = 300 pc, corresponding to the CO emission ring. In the NGC 4968 galaxy, the torques exerted on the gas by the bar are positive in the centre, within the gas nuclear ring, and negative outside. This shows that the gas is transiently trapped in the ILR. The comparison of the CO intensity maps with the map of the cold dust emission shows an absence of CO in the centre of NGC 4968; also the dust distribution and CO emission in and around the centre of NGC 4845 have similar extensions. The 1.2 mm ALMA continuum is peaked and compact in NGC 4968 and MCG-06-30-15, but their CO(2-1) emissions have extended distributions. Allowing the CO-to-H2 conversion factor αCO between 0.8 and 3.2, which is typical of nearby galaxies of the same type, the molecular mass M(H2) is estimated to be ∼3 - 12 × 107 M⊙ (NGC 4968), ∼9 - 36 × 107 M⊙ (NGC 4845), and ∼1 - 4 × 107 M⊙ (MCG-06-30-15). Conclusions. We conclude that the observed non-circular motions in the molecular disc of NGC 4968 and likely those seen in NGC 4845 are due to the presence of the bar in the nuclear region. We discuss the possibility that the observed pattern in the kinematics might be a consequence of the presence of AGNs, and this might be the case for NGC 4845. At the current spectral and spatial resolution and sensitivity, we cannot claim any strong evidence in these sources of the long sought feedback or feeding effect resulting from the presence of AGNs.
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| 17. |
- Fäldt, Åke, 1950, et al.
(författare)
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The gyroscopic effect and moment of inertia
- 2023
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Ingår i: Physics Education. - : IOS Press. - 0031-9120 .- 1361-6552. ; 58:2
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a lab to help students develop their understanding of rotational motion. The focus is on moment of inertia, which the students investigate by rolling cylinders down a ramp and determine in two different ways for a bicycle wheel. The most important and original part of the lab is the exploration of the gyroscopic effect, where measurements of precession and rotation frequencies are made using the variation of the detected magnetic field, enabling the calculation of the moment of inertia. The lab is received well by the students and can be done with relatively simple equipment easily accessible to them.
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| 18. |
- Sundin, Maria, 1965, et al.
(författare)
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Mars - a target for teachers and science students
- 2020
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Ingår i: Contribution to IAU 367S, Education and Heritage in the Era of Big Data in Astronomy, 8-12 December 2020..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A case study is here presented of an interdisciplinary course about Mars for teachers and science students. We aim to share the experience of creating an interdisciplinary approach with lecturers spanning physics, geology, radiation physics and philosophy. Issues in ethics, morality, rights and obligations, conflict management and human psychology as well as rocket orbits, fuel economy, radiation hazards and knowledge of the solar system have proven to be a valued and successful initiative for the further training of teachers and science students. The focus of the course is on planning for a journey with humans to the planet Mars. This provides a great opportunity to package complex societal problems in a physics context. The course is offered with a special sustainability content mark. Mankind has always had a strong and dependent relationship with the physical landscape. The land has given us food and shelter but also imposed challenges and disasters. Understanding the physical environment has been crucial for our survival and development. The same will be equally, or more important for Mars where life conditions are much more extreme. We highlight similarities and differences in the geologic processes that have shaped Earth and Mars. What conditions do the future explorers on Mars have to manage? We then enter the modern era and explore the dynamic Martian landscape of today. Also, by learning to read the landscape we may find locations of shelter such as vast systems of lava tubes, or locations of essential resources such as preserved glacial ice etc. A journey to Mars will cause substantially higher personal irradiation than obtained on Earth. The radiation part of the course lectures starts with defining the different radiation types and the biological effects these different types of radiation will cause. Then, the difference between the irradiation on Earth to the elevated irradiation in space and on Mars is described. Thereafter, it is discussed if this elevated radiation burden can cause acute biological effects, e.g. fatigue, vomiting and death, and late biological effects as cancer induction. Last, possible radiation protection strategies are described and discussed. The philosophy of space exploration consists of philosophical approaches to ethics, presently applied to the topic of Mars exploration and colonization, with environmental ethics (anthropocentric vs ecocentric) and value theory at its core. Four main uses of philosophy are distinguished: ethics, aesthetics, cognition and existentialism. Research has shown that visual representation is an important part for students to be able to create a deeper understanding of concepts as well as context about the material that is taught. Interdisciplinary and complex societal problems have also been shown to be important in science teaching. One way for the teacher to develop his/her teaching is to take further education courses in universities whose focus is to seek and discuss the complex societal problems as well as its solutions from a physics and teacher perspective. Future research could be done on the impact of this course on the education in different levels.
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| 19. |
- Diamantidis, Periklis, 1988, et al.
(författare)
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Evaluation of the first three years of VGOS 24 h sessions using a Kalman filter with C5+
- 2023
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Ingår i: Earth, Planets and Space. - 1880-5981 .- 1343-8832. ; 75:1
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Tidskriftsartikel (refereegranskat)abstract
- We analyzed the first three years of VGOS 24 h sessions, and evaluated the performance in terms of Earth orientation parameters (EOP) and station positions. We estimated radio source coordinates which might be of particular importance in VGOS due to the different observing frequencies compared to legacy S/X VLBI. We investigated the impact of this procedure in the determination of the celestial reference, and detected possible increased crosstalk between radio source positions and nutation. We, thus, created an updated source coordinate catalogue that contains information from the VGOS observations and utilized that as our a priori for further analysis. We found that this procedure significantly attenuates mean biases in the estimated EOP time series. We then utilized a kalman filter with an empirically tuned stochastic modelling for nutation and polar motion and estimated repeatabilities on the 60–80 as level for nutation, and 100–130 as level for polar motion. The station position repeatabilities were evaluated to be 1.80 and 2.12 mm for the east and north components and 3.98 mm for the vertical, while the baseline length repeatabilities were estimated to be 4.22 mm at 6000 km. These results are promising with respect to the expected future VGOS performance, while increased attention should be paid to the celestial frame determination in the VGOS observing bands.
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| 20. |
- Deline, A., et al.
(författare)
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The atmosphere and architecture of WASP-189 b probed by its CHEOPS phase curve
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 659
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Tidskriftsartikel (refereegranskat)abstract
- Context. Gas giants orbiting close to hot and massive early-type stars can reach dayside temperatures that are comparable to those of the coldest stars. These 'ultra-hot Jupiters' have atmospheres made of ions and atomic species from molecular dissociation and feature strong day-to-night temperature gradients. Photometric observations at different orbital phases provide insights on the planet's atmospheric properties. Aims. We aim to analyse the photometric observations of WASP-189 acquired with the Characterising Exoplanet Satellite (CHEOPS) to derive constraints on the system architecture and the planetary atmosphere. Methods. We implemented a light-curve model suited for an asymmetric transit shape caused by the gravity-darkened photosphere of the fast-rotating host star. We also modelled the reflective and thermal components of the planetary flux, the effect of stellar oblateness and light-travel time on transit-eclipse timings, the stellar activity, and CHEOPS systematics. Results. From the asymmetric transit, we measure the size of the ultra-hot Jupiter WASP-189 b, R-p = 1.600(-0.016)(+0.017)R(J), with a precision of 1%, and the true orbital obliquity of the planetary system, Psi(P) = 89.6 +/- 1.2 deg (polar orbit). We detect no significant hotspot offset from the phase curve and obtain an eclipse depth of delta ecl = 96.5(-5.9)(+4).(5) ppm, from which we derive an upper limit on the geometric albedo: A(g) < 0.48. We also find that the eclipse depth can only be explained by thermal emission alone in the case of extremely inefficient energy redistribution. Finally, we attribute the photometric variability to the stellar rotation, either through superficial inhomogeneities or resonance couplings between the convective core and the radiative envelope. Conclusions. Based on the derived system architecture, we predict the eclipse depth in the upcoming Transiting Exoplanet Survey Satellite (TESS) observations to be up to similar to 165 ppm. High-precision detection of the eclipse in both CHEOPS and TESS passbands might help disentangle reflective and thermal contributions. We also expect the right ascension of the ascending node of the orbit to precess due to the perturbations induced by the stellar quadrupole moment J(2) (oblateness).
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