Photometric and spectroscopic variability of the FUor star V582 Aurigae^⋆

¹ Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose blvd., 1784 Sofia, Bulgaria
e-mail: esemkov@astro.bas.bg
² INAF Osservatorio Astronomico di Padova, Sede di Asiago, 36032 Asiago ( VI), Italy
³ Institut d’Astrophysique de Paris, CNRS, and Université Pierre et Marie Curie, 98 bis Boulevard Arago, 75014 Paris, France
⁴ Kiso Observatory, Institute of Astronomy, School of Science, the University of Tokyo, Mitake-mura, Kiso-gun, 397-0101 Nagano-ken, Japan

Received: 18 April 2013
Accepted: 12 June 2013

Abstract

Aims. We present results from optical photometric and spectroscopic observations of the eruptive pre-main sequence star V582 Aur. Variability of the star was reported a few years ago when it was suspected as a possible FU Orionis object. Due to the small number of currently known FUors, a new object of this type is ideal target for follow-up photometric and spectroscopic observations.

Methods. We carried out BVRI CCD photometric observations in the field of V582 Aur from 2009 August to 2013 February. We acquired high-, medium-, and low-resolution spectroscopy of V582 Aur during this period. To study the pre-outburst variability of the target and construct its historical light curve, we searched for archival observations in photographic plate collections. Both CCD and photographic observations were analyzed using a sequence of 14 stars in the field of V582 Aur calibrated in BVRI.

Results. The pre-outburst photographic observations of V582 Aur show low-amplitude light variations typical of T Tauri stars. Archival photographic observations indicate that the increase in brightness began in late 1984 or early 1985 and the star reached the maximum level of brightness at 1986 January. The spectral type of V582 Aur can be defined as G0I with strong P Cyg profiles of Hα and Na I D lines, which are typical of FU Orionis objects. Our BVRI photometric observations show large amplitude variations (ΔV ~ 2m.8) during the 3.5 year period of observations. Most of the time, however, the star remains in a state close to the maximum brightness. The deepest drop in brightness was observed in the spring of 2012, when the brightness of the star fell to a level close to the pre-outburst. The multicolor photometric data show a color reversal during the minimum in brightness, which is typical of UX Ori variables. The corresponding spectral observations show strong variability in the profiles and intensities of the spectral lines (especially Hα), which indicate significant changes in the accretion rate. On the basis of photometric monitoring performed over the past three years, the spectral properties of the maximal light, and the shape of the long-term light curve, we confirm the affiliation of V582 Aur to the group of FU Orionis objects.