OHNAKA , Keiichi

We study the close circumstellar environment of the nearby S-type star Pi^1 Gruis using high spatial-resolution, mid-infrared observations from the ESO/VLTI. Spectra and visibilities were obtained with the MIDI interferometer on the VLT Auxiliary Telescopes. The cool M5III giant Beta Gruis was used as bright primary calibrator, and a dedicated...

Context. Betelgeuse is the closest red supergiant (RSG), therefore it is well suited to study the complex processes in its atmosphere that lead to the chemical enrichment of the interstellar medium. Aims. We intend to investigate the shape and composition of the close molecular layer (also known as the MOLsphere) that surrounds the star. This...

Most Wolf-Rayet stars (WR) of WC9 sub-type exhibit a dusty circumstellar envelope, but it is still a matter of debate how dust can form in their harsh environment. In a few cases, a pinwheel-like structure of the dusty envelope has been detected. Therefore, it has been suggested that dust formation in all dusty WR stars might be linked to...

We present the first interferometric NIR observations of the LBV ? Carinae with high spectral resolution. The observations were carried out with three 8.2 m VLTI Unit Telescopes in the K-band. The raw data are spectrally dispersed interferograms obtained with spectral resolutions of 1,500 (MR-K mode) and 12,000 (HR-K mode). The observations...

High spatial resolution is the key for the understanding various astrophysical phenomena. But even with the future E-ELT, single dish instruments are limited to a spatial resolution of about 4 mas in the visible. For the closest objects within our Galaxy most of the stellar photosphere remains smaller than 1 mas. With the success of long...