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Statistics of BY Draconis chromospheric variable stars
de Grijs, Richard; Kamath, Devika; Chen, Xiaodian +1 more
We present an extensive catalogue of BY Draconis (BY Dra)-type variables and their stellar parameters. BY Dra are main-sequence FGKM-type stars. They exhibit inhomogeneous starspots and bright faculae in their photospheres. These features are caused by stellar magnetic fields, which are carried along with the stellar disc through rotation and whic…
High-contrast, high-angular resolution view of the GJ 367 exoplanet system
Brandner, Wolfgang; Calissendorff, Per; Cantalloube, Faustine +1 more
We search for additional companions in the GJ 367 exoplanet system and aim to better constrain its age and evolutionary status. We analyse high-contrast direct imaging observations obtained with HST/NICMOS, VLT/NACO, and VLT/SPHERE. We investigate and critically discuss conflicting age indicators based on theoretical isochrones and models for Gala…
Peculiar hydrogen-deficient carbon stars: strontium-rich stars and the s-process
Clayton, Geoffrey C.; Tisserand, Patrick; Crawford, Courtney L. +1 more
Context. R Coronae Borealis (RCB) variables and their non-variable counterparts, the dustless Hydrogen-deficient Carbon (dLHdC) stars have been known to exhibit enhanced s-processed material on their surfaces, especially Sr, Y, and Ba. No comprehensive work has been done to explore the s-process in these types of stars, however one particular RCB …
Chemically Peculiar Stars in the Open Cluster Stock 2
Bouy, Hervé; Agüeros, Marcel A.; Gebran, Marwan +2 more
The recently rediscovered open cluster Stock 2, located roughly 375 pc away and about 400 Myr old, has the potential to be an exciting new testbed for our understanding of stellar evolution. We present results from a spectroscopic campaign to characterize stars near the cluster's main-sequence turnoff; our goal is to identify candidate chemically …
Galactic Cosmic Rays at Mars and Venus: Temporal Variations from Hours to Decades Measured as the Background Signal of Onboard Microchannel Plates
Barabash, Stas; Nilsson, Hans; Holmström, Mats +8 more
A microchannel plate (MCP) is a component widely used for counting particles in space. Using the background counts from MCPs on the Mars Express and Venus Express orbiters-operating over 17 yr and 8 yr, respectively-we investigated the galactic cosmic ray (GCR) characteristics of the inner solar system. The MCP background counts at Mars and Venus,…
Evidence of globular cluster abundance anomalies in the SMC intermediate-age cluster Kron 3
Da Costa, G. S.; Milone, A. P.; Marino, A. F. +5 more
Using spectra obtained with the VLT/FORS2 and Gemini-S/GMOS-S instruments, we have investigated carbon, nitrogen, and sodium abundances in a sample of red giant members of the Small Magellanic Cloud star cluster Kron 3. The metallicity and luminosity of the cluster are comparable to those of Galactic globular clusters but it is notably younger (ag…
Ionization and Star Formation in the Giant H II Region SMC-N66
Kniazev, A.; Hamann, W. -R.; Sabbi, E. +8 more
The NGC 346 young stellar system and associated N66 giant H II region in the Small Magellanic Cloud are the nearest example of a massive star-forming event in a low metallicity (Z ≈ 0.2Z ⊙) galaxy. With an age of ≲3 Myr this system provides a unique opportunity to study relationships between massive stars and their associated H II regio…
Constraining Europa's Subsolar Atmosphere With a Joint Analysis of HST Spectral Images and Galileo Magnetic Field Data
Saur, J.; Cervantes, S.
We constrain Europa's tenuous atmosphere on the subsolar hemisphere by combining two sets of observations: oxygen emissions at 1,304 and 1,356 Å from Hubble Space Telescope (HST) spectral images and Galileo magnetic field measurements from its closest encounter, the E12 flyby. We describe Europa's atmosphere with three neutral gas species: global …
CaSSIS-based stereo products for Mars after three years in orbit
Mège, Daniel; Pajola, Maurizio; Cremonese, Gabriele +10 more
The Colour and Stereo Surface Imaging System (CaSSIS) on board the ExoMars Trace Gas Orbiter (TGO), operating in push-frame mode, provides multiband images at four different wavelengths thanks to a Filter Strip Assembly with a panchromatic filter and three broadband filters within the visible and near infrared range. The camera acquires stereo pai…
Upstream solar wind speed at comet 67P. Reconstruction method, model comparison, and results
Holmström, M.; Gunell, H.; Futaana, Y. +7 more
Context. Rosetta followed comet 67P at heliocentric distances from 1.25 to 3.6 au. The solar wind was observed for much of this time, but was significantly deflected and to some extent slowed down by the interaction with the coma.
Aims: We use the different changes in the speed of H+ and He2+ when they interact with the …