An international team of astronomers led by E. Tatulli (Grenoble, France) and S. Kraus (Bonn, Germany)  used the unique capability of the VLT near-infrared interferometer, coupled with spectroscopy, to probe the gaseous environment of Herbig Ae/Be stars. These are young stars of intermediate mass (approximately 2 to 10 solar masses), which are still contracting and often show strong line emissions.
In recent years, young stars have been widely studied with near-infrared interferometers, allowing astronomers to study their close environment with high spatial resolution (see for example the A&A special feature on AMBER/VLTI first results, published in March 2007). So far, near-infrared interferometry has been used mostly to probe the dust that closely surrounds young stellar objects. However, dust is only 1% of the total mass of protoplanetary disks, while gas is their main component (99%) and may be responsible for the structure of forming planetary disks.
High-resolution observations of emission spectral lines are then required to trace this gaseous component. Various processes have been proposed as the source of emission lines. For example, they might come from an accreting gaseous inner disk or might be due to either magnetospheric accretion processes or to a stellar wind. Most of these processes would take place close to the star (less than 1 AU), and are therefore not accessible with direct imaging facilities.
Using the capabilities of AMBER/VLTI, including milli-arcsecond spatial resolution , the team has now been able to trace the inner gaseous environment of six Herbig Ae/Be stars. They measured the geometry and position of the emitting regions surrounding these stars, for several diagnostic emission lines . For two Herbig Be stars, they find that the emission line is probably associated with mass infall; in one case (51 Ophiuchi), the emission line could originate within a dust-free hot gaseous disk. In the other one (HD 98922), the emitting region is very compact and might originate from magnetospheric accretion, through which the material is transported from the disk to the stellar surface. For the four other Herbig Ae/Be stars that have been observed, the emission line would be related to mass outflow, with gas lifted from the surface of a circumstellar disk and then ejected from the stellar system.
Until now, the origin of the gas emission from these young stars was still being debated, because in most earlier investigations of the gas component, the spatial resolution was not high enough to study the gas distribution close to the star. Applying the new high-resolution feature of the AMBER instrument to gas emission observations, the team was then able to show that the gas emission can distinctly trace the physical processes acting close to the star.
 The team includes S. Kraus, K.-H. Hofmann, A. Meilland, N. Nardetto, T. Preibisch, D. Schertl, G. Weigelt (MPI, Bonn, Germany), E. Tatulli (INAF, Italy / Laboratoire d'Astrophysique de Grenoble, France), M. Benisty, J.-P. Berger, F. Malbet, F. Ménard (Laboratoire d'Astrophysique de Grenoble, France), O. Chesneau, P. Stee, (OCA, France), A. Natta (INAF, Italy), M. Smith (Univ. of Kent, UK), C. Gil, L. Testi (ESO), and S. Robbe-Dubois (Université de Nice, France).
 Observing the Moon with milli-arcsecond resolution, one should be able to distinguish details about 2 meters in size.
 They used the Brackett-Γ line of hydrogen at 2.166 µm and the CO emission feature at 2.3 µm as diagnostic lines.
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22.10.2019 | Tata Institute of Fundamental Research
A cavity leads to a strong interaction between light and matter
22.10.2019 | Universität Basel
Researchers have succeeded in creating an efficient quantum-mechanical light-matter interface using a microscopic cavity. Within this cavity, a single photon is emitted and absorbed up to 10 times by an artificial atom. This opens up new prospects for quantum technology, report physicists at the University of Basel and Ruhr-University Bochum in the journal Nature.
Quantum physics describes photons as light particles. Achieving an interaction between a single photon and a single atom is a huge challenge due to the tiny...
A very special kind of light is emitted by tungsten diselenide layers. The reason for this has been unclear. Now an explanation has been found at TU Wien (Vienna)
It is an exotic phenomenon that nobody was able to explain for years: when energy is supplied to a thin layer of the material tungsten diselenide, it begins to...
Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols.
The nanocosmos is constantly in motion. All natural processes are ultimately determined by the interplay between radiation and matter. Light strikes particles...
Particles that are mere nanometers in size are at the forefront of scientific research today. They come in many different shapes: rods, spheres, cubes, vesicles, S-shaped worms and even donut-like rings. What makes them worthy of scientific study is that, being so tiny, they exhibit quantum mechanical properties not possible with larger objects.
Researchers at the Center for Nanoscale Materials (CNM), a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE's Argonne National...
A new research project at the TH Mittelhessen focusses on the development of a novel light weight design concept for leisure boats and yachts. Professor Stephan Marzi from the THM Institute of Mechanics and Materials collaborates with Krake Catamarane, which is a shipyard located in Apolda, Thuringia.
The project is set up in an international cooperation with Professor Anders Biel from Karlstad University in Sweden and the Swedish company Lamera from...
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