The ongoing 2008–09 outburst of CI Cyg |
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| Authors: | A Siviero U Munari S Dallaporta P Valisa V Luppi S Moretti S Tomaselli S Bacci F Ballardini G Cherini M Graziani A Frigo A Vagnozzi |
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| Institution: | INAF Astronomical Observatory of Padova, 36012 Asiago (VI), Italy;Astrophysikalisches Institut Potsdam, Potsdam, Germany;ANS Collaboration, c/o Osservatorio Astronomico, via dell'Osservatorio 8, 36012 Asiago (VI), Italy |
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| Abstract: | In this paper, we discuss the early phases of the ongoing outburst that CI Cyg, a prototype symbiotic star, is currently undergoing after 30-year quiescence. We have tightly monitored CI Cyg in B V R C I C bands, starting a whole year before the onset of the outburst, and in addition we obtained numerous Echelle high- and low-resolution absolutely flux-calibrated spectra. The outburst started while the accreting white dwarf (WD) was being eclipsed by the Roche lobe filling M giant companion, and it was discovered during the egress phase on the second half of 2008 August. The system reached peak V -band brightness in early 2008 October and has been characterized by amplitudes Δ B = 1.9, Δ V = 1.5, Δ R C= 0.9, Δ I C= 0.4 mag. At maximum V -band brightness, the outbursting WD had expanded to closely resemble an F3 II/Ib star, with MV =?3.5, T eff～ 6900 K and R = 28 R⊙ . The high-ionization emission lines (Ne v ], Fe vii ], He ii ) disappeared and only lower ionization lines were visible. Balmer and He i emission lines declined in equivalent width but increased in absolute flux. The output radiated by the hot component during the outburst corresponds to nuclear burning proceeding at a 2 × 10?8 M⊙ yr?1 rate. |
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| Keywords: | binaries: symbiotic novae cataclysmic variables |
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