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.
Temperature-controlled fiber-optic light source with liquid core
20.06.2018 | Leibniz-Institut für Photonische Technologien e. V.
New material for splitting water
19.06.2018 | American Institute of Physics
In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.
Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...
Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
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21.06.2018 | Earth Sciences