Planets and Planet-Sized Binaries from the OGLE Transit Survey

The OGLE survey for transiting planets has identified 177 transit candidates. Subsequent radial velocity follow-up of these candidates has allowed the detection of five transiting planets, as well as several dozen eclipsing binaries.Some of these systems consist of solar-type stars transited by small M dwarf companion, including the smallest stellar companions yet measured by transit. As a result, the OGLE transit survey has yielded a wealth of data on the mass-radius relation of planets and low-mass stars. In particular, two planet-sized stars were found, an empirical proof of the model predictions on Jupiter-sized main-sequence stars.     

Polarization in the young cluster NGC 6611: circumstellar, interstellar, or ... both?

We obtained linear polarization observations of 82 A/B-type stars in the young cluster NGC 6611, in order to probe the circumstellar material and to search for any evidence of intracluster or interstellar material that could also contribute to the polarization. We found linear polarization values that reach up to 14%. We consider the distribution of the polarization, its position angle, correlations with extinction and membership probability, polarization variability and wavelength distribution to identify the origin of the polarization toward NGC 6611. The polarization is found to be dominated by interstellar polarization, although some stars also have some circumstellar polarization. There is no evidence for intracluster dust. Rather, the dust must be located in a low density cloud toward the general line of sight to NGC 6611 and in front of it. The depth of that cloud along the line of sight increases slowly from the south–east to the north–west. The cloud is threaded by a very uniform magnetic field.     

Multi-Scale Analysis of Magnetic Fields in Filamentary Molecular Clouds

Using polarimetry, at both visible and submillimeter wavelengths, we propose to study the role and to compare the structure of the magnetic fields within and near filamentary molecular clouds. The optical polarization data obtained at Mont Mégantic and from the Heiles catalog constrain the large scale topology of magnetic fields in the near environment of the clouds. Submillimeter data probe the structure of the field at smaller scale within the clouds. The aim of this research is to put constraints on the way the magnetic field threading the filaments connects to larger structures in the ISM. This should help to illuminate the large scale topology of the field, which is crucial to understanding the formation of filaments and the role of magnetic fields within these structures. Two different regions have been selected for this project, OMC where star formation actively occurs and CL04/CL21 which is a cold molecular filament in the earliest stages of stellar formation.     

Magmatism at continental passive margins inferred from Ambient‐Noise Phase‐velocity in the Gulf of Aden

Non‐volcanic continental passive margins have traditionally been considered to be tectonically and magmatically inactive once continental breakup has occurred and seafloor spreading has commenced. We use ambient‐noise tomography to constrain Rayleigh‐wave phase‐velocity maps beneath the eastern Gulf of Aden (eastern Yemen and southern Oman). In the crust, we image low velocities beneath the Jiza‐Qamar (Yemen) and Ashawq‐Salalah (Oman) basins, likely caused by the presence of partial melt associated with magmatic plumbing systems beneath the rifted margin. Our results provide strong evidence that magma intrusion persists after breakup, modifying the composition and thermal structure of the continental margin. The coincidence between zones of crustal intrusion and steep gradients in lithospheric thinning, as well as with transform faults, suggests that magmatism post‐breakup may be driven by small‐scale convection and enhanced by edge‐driven flow at the juxtaposition of lithosphere of varying thickness and thermal age.     

Seismic‐stratigraphic record of a deglaciation sequence: from the marine Laflamme Gulf to Lake Saint‐Jean (late Quaternary,Québec,Canada)

The stratigraphy of the last deglaciation sequence is investigated in Lake Saint‐Jean (Québec Province, Canada) based on 300 km of echo‐sounder two dimensional seismic profiles. The sedimentary archive of this basin is documented from the Late Pleistocene Laurentidian ice‐front recession to the present‐day situation. Ten seismic units have been identified that reflect spatio‐temporal variations in depositional processes characterizing different periods of the Saint‐Jean basin evolution. During the postglacial marine flooding, a high deposition rate of mud settling, from proglacial glacimarine and then prodeltaic plumes in the Laflamme Gulf, produced an extensive, up to 50 m thick mud sheet draping the isostatically depressed marine basin floor. Subsequently, a closing of the water body due to glacio‐isostatic rebound occurred at 8.5 cal. ka BP, drastically modifying the hydrodynamics. Hyperpycnal flows appeared because fresh lake water replaced dense marine water. River sediments were transferred towards the deeper part of the lake into river‐related sediment drifts and confined lobes. The closing of the water body is also marked by the onset of a wind‐driven internal circulation associating coastal hydrodynamics and bottom currents with sedimentary features including shoreface deposits, sediment drifts and a prograding shelf‐type body. The fingerprints of a forced regression are well expressed by mouth‐bar systems and by the shoreface–shelf system, the latter unexpected in such a lacustrine setting. In both cases, a regressive surface of lacustrine erosion (RSLE) has been identified, separating sandy mouth‐bar from glaciomarine to prodeltaic muds, and sandy shoreface wedges from the heterolithic shelf‐type body, respectively. The Lake Saint‐Jean record is an example of a regressive succession driven by a glacio‐isostatic rebound and showing the transition from late‐glacial to post‐glacial depositional systems.