Spectro-astrometry of V1515 cygni

Abstract

Context. FU Orionis objects are a class of young stars with powerful bursts in luminosity that show evidence of accretion and ejection activity. It is generally accepted that they are surrounded by a Keplerian circumstellar disk and an infalling envelope. The outburst occurs because of a sudden increase in the accretion rate. Aims. We study the regions closer to the central star in order to observe the signs of the accretion and ejection activity. Methods. We present optical observations of the Hα line using the Integral Field Spectrograph OASIS, at the William Herschel Telescope, combined with adaptive optics. Since this technique gives the spectral information for both spatial directions, we carried out a two-dimensional spectro-astrometric study of the signal. Results. We measured a clear spectro-astrometric signal in the north-south direction. The cross-correlation between the spectra showed a spatial distribution in velocity suggestive of scattering by a disk surrounding the star. This would be one of the few spatial inferences of a disk observed in an FU Orionis object. However, to fully understand the observed structure, higher angular and spectral resolution observations are required. V1515 Cyg now appears to be an important object to be observed with a new generation of instruments to increase our knowledge about the disk and outflow structure in FU Orionis objects. © 2014 ESO.