The star in RNO 54 -- a post-FUor with short faint jet?

Abstract

The aim of the present study was the spectral analysis of an unusual pre-main-sequence star in the cometary nebula RNO 54, which was suspected by several researchers as a FUori-like object. We performed long-slit spectroscopy of the star on the 6-m telescope with the SCORPIO-2 multi-mode focal reducer. We discover a short ($\sim4$ arcsec or $\sim6000$ AU) and faint emission shock-excited jet from this star, probably oriented toward the long axis of the nebular ellipse. The spectral type of the star is estimated as G0-2 II; the split of absorption Li I line which is a typical sign indicating the FUori-like spectrum, is confirmed. The analysis of the available data shows virtual absence of the photometric variability, for at least the last 20 years. The lower limit of the bolometric luminosity of the star is estimated as 300 Lsun. Our study supports the classification of RNO 54 star as a FUor-like object in the long-after-outburst stage.