As the nearest known AGB star ( d = 64 pc ) and one of the brightest ( m _ { K } \approx - 2 ) , L _ { 2 } Pup is a particularly interesting benchmark object to monitor the final stages of stellar evolution .
We report new serendipitous imaging observations of this star with the VLT/NACO adaptive optics system in twelve narrow-band filters covering the 1.0 - 4.0 \mu m wavelength range .
These diffraction-limited images reveal an extended circumstellar dust lane in front of the star that exhibits a high opacity in the J band and becomes translucent in the H and K bands .
In the L band , extended thermal emission from the dust is detected .
We reproduced these observations using Monte Carlo radiative transfer modeling of a dust disk with the RADMC-3D code .
We also present new interferometric observations with the VLTI/VINCI and MIDI instruments .
We measured in the K band an upper limit to the limb-darkened angular diameter of \theta _ { \mathrm { LD } } = 17.9 \pm 1.6 mas , converting to a maximum linear radius of R = 123 \pm 14 R _ { \odot } .
Considering the geometry of the extended K band emission in the NACO images , this upper limit is probably close to the actual angular diameter of the star .
The position of L _ { 2 } Pup in the Hertzsprung-Russell diagram indicates that this star has a mass of about 2 M _ { \odot } and is probably experiencing an early stage of the asymptotic giant branch .
We did not detect any stellar companion of L _ { 2 } Pup in our adaptive optics and interferometric observations , and we attribute its apparent astrometric wobble in the Hipparcos data to variable lighting effects on its circumstellar material .
However , we do not exclude the presence of a binary companion , because the large loop structure extending to more than 10 AU to the northeast of the disk in our L -band images may be the result of interaction between the stellar wind of L _ { 2 } Pup and a hidden secondary object .
The geometric configuration that we propose , with a large dust disk seen almost edge-on , appears particularly favorable to test and develop our understanding of the formation of bipolar nebulae .