2015A&A...581A.127O

The red giant L₂ Pup started a dimming event in 1994, which is considered to be caused by the ejection of dust clouds. We present near-IR aperture-synthesis imaging of L₂ Pup achieved by combining data from VLT/NACO and the AMBER instrument of the Very Large Telescope Interferometer (VLTI). Our aim is to spatially resolve the innermost region of the circumstellar environment. We carried out speckle interferometric observations at 2.27µm with VLT/NACO and long-baseline interferometric observations with VLTI/AMBER at 2.2-2.35µm with baselines of 15-81m. We also extracted an 8.7µm image from the mid-IR VLTI instrument MIDI. The diffraction-limited image obtained by bispectrum speckle interferometry with NACO with a spatial resolution of 57mas shows an elongated component. The aperture-synthesis imaging combining the NACO speckle data and AMBER data with a spatial resolution of 5.6x7.3mas further resolves not only this elongated component, but also the central star. The reconstructed image reveals that the elongated component is a nearly edge-on disk with a size of ∼180x50mas lying in the E-W direction, and furthermore, that the southern hemisphere of the central star is severely obscured by the equatorial dust lane of the disk. The angular size of the disk is consistent with the distance that the dust clouds that were ejected at the onset of the dimming event should have traveled by the time of our observations, if we assume that the dust clouds moved radially. This implies that the formation of the disk may be responsible for the dimming event. The 8.7µm image with a spatial resolution of 220mas extracted from the MIDI data taken in 2004 (seven years before the AMBER and NACO observations) shows an approximately spherical envelope without a signature of the disk. This suggests that the mass loss before the dimming event may have been spherical.