| 1. |
- Bonfanti, A., et al.
(författare)
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Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley ★,★★
- 2024
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 682
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Tidskriftsartikel (refereegranskat)abstract
- TOI-732 is an M dwarf hosting two transiting planets that are located on the two opposite sides of the radius valley. Inferring a reliable demographics for this type of systems is key to understanding their formation and evolution mechanisms. Aims. By doubling the number of available space-based observations and increasing the number of radial velocity (RV) measurements, we aim at refining the parameters of TOI-732 b and c. We also use the results to study the slope of the radius valley and the density valley for a well-characterised sample of M-dwarf exoplanets. Methods. We performed a global Markov chain Monte Carlo analysis by jointly modelling ground-based light curves and CHEOPS and TESS observations, along with RV time series both taken from the literature and obtained with the MAROON-X spectrograph. The slopes of the M-dwarf valleys were quantified via a support vector machine (SVM) procedure. Results. TOI-732 b is an ultrashort-period planet (P = 0.76837931−+000000004200000039 days) with a radius Rb = 1.325+−00057058 R☉, a mass Mb = 2.46 ± 0.19 M☉, and thus a mean density ρb = 5.8+−1008 g cm−3, while the outer planet at P = 12.252284 ± 0.000013 days has Rc = 2.39+−001011 R☉, Mc = 8.04+−005048 M☉, and thus ρc = 3.24+−005543 g cm−3. Even with respect to the most recently reported values, this work yields uncertainties on the transit depths and on the RV semi-amplitudes that are smaller up to a factor of ∼1.6 and ∼2.4 for TOI-732 b and c, respectively. Our calculations for the interior structure and the location of the planets in the mass-radius diagram lead us to classify TOI-732 b as a super-Earth and TOI-732 c as a mini-Neptune. Following the SVM approach, we quantified d log Rp,valley/d log P = −0.065+−00024013, which is flatter than for Sun-like stars. In line with former analyses, we note that the radius valley for M-dwarf planets is more densely populated, and we further quantify the slope of the density valley as d log ρ̂valley/d log P = −0.02+−001204. Conclusions. Compared to FGK stars, the weaker dependence of the position of the radius valley on the orbital period might indicate that the formation shapes the radius valley around M dwarfs more strongly than the evolution mechanisms.
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| 2. |
- Chaturvedi, P., et al.
(författare)
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TOI-1468: A system of two transiting planets, a super-Earth and a mini-Neptune, on opposite sides of the radius valley
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery and characterization of two small transiting planets orbiting the bright M3.0V star TOI-1468 (LSPM J0106+1913), whose transit signals were detected in the photometric time series in three sectors of the TESS mission. We confirm the planetary nature of both of them using precise radial velocity measurements from the CARMENES and MAROON-X spectrographs, and supplement them with ground-based transit photometry. A joint analysis of all these data reveals that the shorter-period planet, TOI-1468 b (P-b = 1.88 d), has a planetary mass of M-b = 3.21 +/- 0.24M(circle plus) and a radius of R-b = 1.280(-0.039)(+0.038) R-circle plus, resulting in a density of rho(b) = 8.39(-0.92)(+1.05) g cm(-3), which is consistent with a mostly rocky composition. For the outer planet, TOI-1468 c (P-c = 15.53 d), we derive a mass of M-c = 6.64(-0.68)(+0.67) M-circle plus,aradius of R-c = 2.06 +/- 0.04 R-circle plus, and a bulk density of rho(c) = 2.00(-0.19)(+0.21) g cm(-3), which corresponds to a rocky core composition with a H/He gas envelope. These planets are located on opposite sides of the radius valley, making our system an interesting discovery as there are only a handful of other systems with the same properties. This discovery can further help determine a more precise location of the radius valley for small planets around M dwarfs and, therefore, shed more light on planet formation and evolution scenarios.
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| 3. |
- Pfeffer, M. A., et al.
(författare)
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Ground-Based measurements of the 2014-2015 holuhraun volcanic cloud (Iceland)
- 2018
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Ingår i: Geosciences (Switzerland). - : MDPI AG. - 2076-3263. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The 2014-2015 Bárðarbunga fissure eruption at Holuhraun in central Iceland was distinguished by the high emission of gases, in total 9.6 Mt SO 2 , with almost no tephra. This work collates all ground-based measurements of this extraordinary eruption cloud made under particularly challenging conditions: remote location, optically dense cloud with high SO 2 column amounts, low UV intensity, frequent clouds and precipitation, an extensive and hot lava field, developing ramparts, and high-latitude winter conditions. Semi-continuous measurements of SO 2 flux with three scanning DOAS instruments were augmented by car traverses along the ring-road and along the lava. The ratios of other gases/SO 2 were measured by OP-FTIR, MultiGAS, and filter packs. Ratios of SO 2 /HCl = 30-110 and SO 2 /HF = 30-130 show a halogen-poor eruption cloud. Scientists on-site reported extremely minor tephra production during the eruption. OPC and filter packs showed low particle concentrations similar to non-eruption cloud conditions. Three weather radars detected a droplet-rich eruption cloud. Top of eruption cloud heights of 0.3-5.5 km agl were measured with ground-and aircraft-based visual observations, web camera and NicAIR II infrared images, triangulation of scanning DOAS instruments, and the location of SO 2 peaks measured by DOAS traverses. Cloud height and emission rate measurements were critical for initializing gas dispersal simulations for hazard forecasting.
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| 4. |
- Stefansson, Gunnar, 1963, et al.
(författare)
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Processes and operations cases
- 2011
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Ingår i: Sustainable Supply Chain Management: Practical Ideas for Moving Towards Best Practice. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783642120220 ; , s. 213-258
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In order to lower logistics costs and increase efficiency in its transportation and warehousing operations, IKEA started an internal competition to reduce unnecessary air in their product packaging. This Air hunting competition focused on removing as much air as possible from packaging and thereby increasing true product volume during transportation and storage. Several IKEA products were identified for packaging development, one being the Glimma tea candle that is described in this best practice documentation. The development of the Glimma tea candle packaging resulted in a 30% increase in products volume for each load unit. Thanks to this packaging development, the efficiency of the transportation and warehouse operations is now much greater and the impact on the environment has decreased significantly.
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