Volume 523, November-December 2010
|Number of page(s)||4|
|Published online||15 November 2010|
Letter to the Editor
The large amplitude outburst of the young star HBC 722 in NGC 7000/IC 5070, a new FU Orionis candidate
Institute of Astronomy and National Astronomical Observatory, Bulgarian
Academy of Sciences, 72
Tsarigradsko Shose blvd., 1784
2 INAF Osservatorio Astronomico di Padova, Sede di Asiago, 36032 Asiago (VI), Italy
3 ANS Collaboration, Astronomical Observatory, 36012 Asiago (VI), Italy
Accepted: 27 October 2010
Context. The investigations of the photometric and spectral variability of PMS stars are essential to a better understanding of the early phases of stellar evolution. We are carrying out a photometric monitoring program of some fields of active star formation. One of our targets is the dark cloud region between the bright nebulae NGC 7000 and IC 5070.
Aims. We report the discovery of a large amplitude outburst from the young star HBC 722 (LkHα 188 G4) located in the region of NGC 7000/IC 5070. On the basis of photometric and spectroscopic observations, we argue that this outburst is of the FU Orionis type.
Methods. We gathered photometric and spectroscopic observations of the object both in the pre-outburst state and during a phase of increase in its brightness. The photometric BVRI data (Johnson-Cousins system) that we present were collected from April 2009 to September 2010. To facilitate transformation from instrumental measurements to the standard system, fifteen comparison stars in the field of HBC 722 were calibrated in the BVRI bands. Optical spectra of HBC 722 were obtained with the 1.3-m telescope of Skinakas Observatory (Crete, Greece) and the 0.6-m telescope of Schiaparelli Observatory in Varese (Italy).
Results. The pre-outburst photometric and spectroscopic observations of HBC 722 show both low amplitude photometric variations and an emission-line spectrum typical of T Tau stars. The observed outburst started before May 2010 and reached its maximum brightness in September 2010, with a recorded ΔV ~ 4ṃ7 amplitude. Simultaneously with the increase in brightness the color indices changed significantly and the star became appreciably bluer. The light curve of HBC 722 during the period of rise in brightness is similar to the light curves of the classical FUors – FU Ori and V1057 Cyg. The spectral observations during the time of increase in brightness showed significant changes in both the profiles and intensity of the spectral lines. Only Hα remained in emission, while the Hβ, Na I 5890/5896, Mg I triplet 5174, and Ba II 5854/6497 lines were in strong absorption.
Key words: stars: pre-main sequence / stars: variables: T Tauri, Herbig Ae/Be / stars: individual: HBC 722
© ESO, 2010
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.