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- Rodet, L., et al.
(författare)
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Dynamical masses of M-dwarf binaries in young moving groups I. The case of TWA22 and GJ2060
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 618
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Tidskriftsartikel (refereegranskat)abstract
- Context. Evolutionary models are widely used to infer the mass of stars, brown dwarfs, and giant planets. Their predictions are thought to be less reliable at young ages (<200 Myr) and in the low-mass regime (< 1 M-circle dot). GJ 2060AB and TWA22AB are two rare astrometric M-dwarf binaries, respectively members of the AB Doradus (AB Dor) and Beta Pictoris (beta Pic) moving groups. As their dynamical mass can be measured to within a few years, they can be used to calibrate the evolutionary tracks and set new constraints on the age of young moving groups.Aims. We provide the first dynamical mass measurement of GJ 2060 and a refined measurement of the total mass of TWA22. We also characterize the atmospheric properties of the individual components of GJ 2060 that can be used as inputs to the evolutionary models.Methods. We used NaCo and SPHERE observations at VLT and archival Keck/NIRC2 data to complement the astrometric monitoring of the binaries. We combined the astrometry with new HARPS radial velocities (RVs) and FEROS RVs of GJ 2060. We used a Markov chain MonteCarlo (MCMC) module to estimate posteriors on the orbital parameters and dynamical masses of GJ 2060AB and TWA22AB from the astrometry and RVs. Complementary data obtained with the integral field spectrograph VLT /SINFONI were gathered to extract the individual near-infrared (1.1-2.5 mu m) medium-resolution (R similar to 1500 2000) spectra of GJ 2060A and B. We compared the spectra to those of known objects and to grids of BT-SETTL model spectra to infer the spectral type, bolometric luminosities, and temperatures of those objects.Results. We find a total mass of 0 : 18 +/- 0 : 02 M-circle dot for TWA22, which is in good agreement with model predictions at the age of the fi Pic moving group. We obtain a total mass of 1 : 09 +/- 0 : 10 M-circle dot for GJ 2060. We estimate a spectral type of M1 +/- 0.5, L/L-circle dot = -1.20 +/- 0.05 dex, and T-eff = 3700 +/- 100 K for GJ 2060 A. The B component is a M3 +/- 0 : 5 dwarf with L/L-circle dot = 1.63 +/- 0.05 dex and T-eff = 3400 +/- 100 K. The dynamical mass of GJ 2060AB is inconsistent with the most recent models predictions (BCAH15, PARSEC) for an AB Dor age in the range 50-150 Myr. It is 10%-20% (1-2 sigma, depending on the assumed age) above the model's predictions, corresponding to an underestimation of 0.10-0.20 M fi. Coevality suggests a young age for the system (similar to 50 Myr) according to most evolutionary models.Conclusions. TWA22 validates the predictions of recent evolutionary tracks at similar to 20 Myr. On the other hand, we evidence a 1-2 sigma mismatch between the predicted and observed mass of GJ 2060 AB. This slight departure may indicate that one of the stars hosts a tight companion. Alternatively, this would confirm the model's tendency to underestimate the mass of young low-mass stars.
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| 2. |
- Walther, G, et al.
(författare)
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Report on challenges for SCIs
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report discusses the challenges posed by four types of threats – terrorist attacks, cyber-attacks, extreme weather and social unrest – on the following eight smart critical infrastructure systems:a.ALPHA - Finance (financial system): The analysis focuses on disturbed information flow and disabling/manipulating IT and communication systems, including attacks on the “physical layer” using the example of IEMI/HPEM threats, as well as the software layer.b. BRAVO - Energy supply (system): The analysis focuses on disruption of “smart” energy supply in a “smart city”, caused by natural hazards, in this case flooding, leading to cascading effects and severe consequences for other energy-depending SCIs.c. CHARLIE - Health care (system):Focus of the analysis is on all threats that might cause large increases in the numbers of injuries or sick patients within a densely populated area. This will include indirect impacts, e.g. large numbers of injuries caused by a disaster or terrorist attacks or disease epidemics, but also direct impacts, e.g. service disruptions in critical health infrastructures, such as hospitals, due to attacks or disasters hitting the infrastructure itself.d.DELTA - Transportation (system) – airports: According to the framework situation, threats on Smart Airports will be assessed under circumstances of (i) blocked traffic, (ii) passenger and airplane traffic exceeding capacity (iii) flood.e. ECHO - Industry (in zones in cities) "Industrial Production Plants":The analysis focuses mainly on technological accidents within the refinery complex, but also accidents caused by natural hazards affecting refinery property outside the main refinery complex, e.g. accident on jetty belonging to refinery on the river Danube during unloading/loading oil products from barge to a tank, damages by a gale or storm on process installations (pipes, hoses) resulting in river pollution. Both scenarios could lead to cascading effects for other SCIs in close vicinity.f. FOXTROT - Water supply (systems): The analysis focuses on three cases of local and regional drinking water supply chains, with different kinds of vulnerabilities in terms of climate threats, ICT challenges, security issues and human error.g.GOLF - Urban flood protection (systems): The analysis focuses in the disruption of water and transport caused through tidal and fluvial flooding events.h. HOTEL: City of Helsinki - Flooding underground coal storage. Resilience of the energy infrastructure (city environment).The way this analysis was conducted was by assessing these threats using a 5x5 framework matrix. The two axes of the matrix were phases (understand risks, anticipate/prepare, absorb/withstand, respond/recover, adapt/learn) and dimensions (system/physical, information/data, organizational/business, societal/political, cognitive/decision-making).Each individual matrix block was discussed by subject experts who identified specific challenges and implications for each matrix element and rated its relevance (high, medium, low).In terms of the results, the system/physical dimension received the highest number of important challenges.Overall, the most important singular element was to understand risks in the organizational/business dimension. The least importance was attributed to the adapt/learn phase.
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