The environment of the fast rotating star Achernar - High-resolution thermal infrared imaging with VISIR in BURST mode

Abstract

Context: The geometry of the circumstellar envelopes (CSE) surrounding Be stars is still uncertain, although it is often assumed that they are formed by a disk around the stellar equator and a hot polar wind. Achernar (Alpha Eri) is the nearest Be star, and we recently detected a CSE using near-IR interferometry. Aims: Our initial goal was to constrain the geometry and flux contribution of the CSE of Achernar at distances of a few tens of AU from the star, in the thermal IR domain to complement our near-IR interferometric observations. Methods: We obtained diffraction-limited images of Achernar in the thermal infrared using VISIR at the VLT. In order to freeze the turbulence, we used the BURST mode of this instrument. Results: The images obtained in the PAH1 band show a point-like source located 0.280" north-west of Achernar (projected linear separation of 12.3 AU). Its emission is 1.8 % of the flux of Achernar in this band, but is not detected in the PAH2, SiC and NeII bands. We also provide new thermal IR photometry of Achernar in four bands. Conclusions: Being aligned with the expected azimuth of the equatorial plane of Achernar, the detected source could be a main sequence stellar companion. In this case, it apparent brightness would correspond to an A7V spectral type.

4 pages, 4 figures

References in corpus (2)

• Testing turbulence model at metric scales with mid-infrared VISIR images at the VLT
• An original interferometric study of NGC 1068 with VISIR BURST mode images

Cited by in corpus (9)

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• The binary system of the spinning-top Be star Achernar
• The environment of the fast rotating star Achernar - Thermal infrared interferometry with VLTI/MIDI and SIMECA modeling
• The impact of the oblateness of Regulus on the motion of its companion
• The nearby eclipsing stellar system delta Velorum - I. Origin of the infrared excess from VISIR and NACO imaging