Research Note

Optical photometric and spectral study of the new FU Orionis object V2493 Cygni (HBC 722)^⋆

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 Physics Department, University of Rijeka, Omladinska 14, 51000 Rijeka, Croatia
⁴ Departamento de Fisica Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, 21071 Huelva, Spain
⁵ Galaxy View Observatory, 102 Galaxy View Ct., Sequim, WA 98382, USA
⁶ Department of Physics, Shumen University, 9700 Shumen, Bulgaria
⁷ Public Astronomical Observatory and Planetarium, Varna, Bulgaria

Received: 29 February 2012
Accepted: 24 April 2012

Abstract

Aims. We present new results from optical photometric and spectroscopic observations of the eruptive pre-main sequence star V2493 Cyg (HBC 722). The object has continued to undergo significant brightness variations over the past few months and is an ideal target for follow-up observations.

Methods. We carried out CCD BVRI photometric observations in the field of V2493 Cyg (“Gulf of Mexico”) from August 1994 to April 2012, i.e. at the pre-outburst states and during the phases of the outburst. We acquired high, medium, and low resolution spectroscopy of V2493 Cyg during the outburst. 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 15 comparison stars in the field of V2493 Cyg.

Results. The pre-outburst photographic and CCD photometric observations of V2493 Cyg show low-amplitude light variations typical of T Tauri stars. The recent photometric data show a slow light decrease from October 2010 to June 2011 followed by an increase in brightness that continued until early 2012. The spectral observations of V2493 Cyg are typical of FU Orionis stars absorption spectra with strong P Cyg profiles of Hα and Na I D lines. On the basis of photometric monitoring performed over the past two years, the spectral properties at the maximal light, as well as the shape of long-term light curves, we confirm that the observed outburst of V2493 Cyg is of FU Orionis type.