Search Publications
Twisted Flux Tube Emergence Evidenced in Longitudinal Magnetograms: Magnetic Tongues
Mandrini, C. H.; van Driel-Gesztelyi, L.; Démoulin, P. +1 more
Bipolar active regions (ARs) are thought to be formed by twisted flux tubes, as the presence of such twist is theoretically required for a cohesive rise through the whole convective zone. We use longitudinal magnetograms to demonstrate that a clear signature of a global magnetic twist is present, particularly, during the emergence phase when the A…
Very Large Telescope/NACO Polarimetric Differential Imaging of HD100546—Disk Structure and Dust Grain Properties between 10 and 140 AU
Henning, Thomas; Brandner, Wolfgang; Meyer, Michael R. +4 more
We present polarimetric differential imaging (PDI) data of the circumstellar disk around the Herbig Ae/Be star HD100546 obtained with Very Large Telescope/NACO. We resolve the disk in polarized light in the H and Ks filter between ~0farcs1 and 1farcs4 (i.e., ~10-140 AU). The innermost disk regions are directly imaged for the first time …
Orbital Motion of HR 8799 b, c, d Using Hubble Space Telescope Data from 1998: Constraints on Inclination, Eccentricity, and Stability
Pueyo, Laurent; Marois, Christian; Rajan, Abhijith +3 more
HR 8799 is currently the only multiple-planet system that has been detected with direct imaging, with four giant planets of masses 7-10 M Jup orbiting at large separations (15-68 AU) from this young late A star. Orbital motion provides insight into the stability and possible formation mechanisms of this planetary system. Dynamical studi…
The peculiar horizontal branch of NGC 2808
Dalessandro, E.; Salaris, M.; Sabbi, E. +5 more
We present an accurate analysis of the peculiar horizontal branch (HB) of the massive Galactic globular cluster NGC 2808, based on high-resolution far-UV and optical images of the central region of the cluster obtained with the Hubble Space Telescope. We confirm the multimodal distribution of stars along the HB: four sub-populations separated by g…
The star cluster - field star connection in nearby spiral galaxies. II. Field star and cluster formation histories and their relation
Larsen, S. S.; Silva-Villa, E.
Context. Recent studies have started to cast doubt on the assumption that most stars are formed in clusters. Observational studies of field stars and star cluster systems in nearby galaxies can lead to better constraints on the fraction of stars forming in clusters. Ultimately this may lead to a better understanding of star formation in galaxies, …
Dusty plasma in the vicinity of Enceladus
Gurnett, D. A.; Persoon, A. M.; Kurth, W. S. +7 more
We present in situ Cassini Radio Plasma Wave Science observations in the vicinity of Enceladus and in the E ring of Saturn that indicate the presence of dusty plasma. The four flybys of Enceladus in 2008 revealed the following cold plasma characteristics: (1) there is a large plasma density (both ions and electrons) within the Enceladus plume regi…
Model of the Jovian magnetic field topology constrained by the Io auroral emissions
Bonfond, B.; Zarka, P.; Grodent, D. +1 more
The determination of the internal magnetic field of Jupiter has been the object of many studies and publications. These models have been computed from the Pioneer, Voyager, and Ulysses measurements. Some models also use the position of the Io footprints as a constraint: the magnetic field lines mapping to the footprints must have their origins alo…
The Stellar Velocity Dispersion of a Compact Massive Galaxy at z = 1.80 Using X-Shooter: Confirmation of the Evolution in the Mass-Size and Mass-Dispersion Relations
van Dokkum, Pieter G.; Franx, Marijn; Labbé, Ivo +7 more
Recent photometric studies have shown that early-type galaxies at fixed stellar mass were smaller and denser at earlier times. In this Letter, we assess that finding by deriving the dynamical mass of such a compact quiescent galaxy at z = 1.8. We have obtained a high-quality spectrum with full UV-NIR wavelength coverage of galaxy NMBS-C7447 using …
Solar Flares and Coronal Mass Ejections: A Statistically Determined Flare Flux - CME Mass Correlation
Hughes, W. J.; Stassun, K. G.; McGregor, S. L. +1 more
In an effort to examine the relationship between flare flux and corresponding CME mass, we temporally and spatially correlate all X-ray flares and CMEs in the LASCO and GOES archives from 1996 to 2006. We cross-reference 6733 CMEs having well-measured masses against 12 050 X-ray flares having position information as determined from their optical c…
Star Formation in 30 Doradus
Mutchler, Max; McCarthy, Patrick J.; Calzetti, Daniela +24 more
Using observations obtained with the Wide-Field Camera 3 on board the Hubble Space Telescope, we have studied the properties of the stellar populations in the central regions of 30 Dor in the Large Magellanic Cloud. The observations clearly reveal the presence of considerable differential extinction across the field. We characterize and quantify t…