Open AccessThe ongoing 2008–09 outburst of CI Cyg
Author(s) -
Siviero A.,
Munari U.,
Dallaporta S.,
Valisa P.,
Luppi V.,
Moretti S.,
Tomaselli S.,
Bacci S.,
Ballardini F.,
Cherini G.,
Graziani M.,
Frigo A.,
Vagnozzi A.
Publication year - 2009
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2009.15414.x
Subject(s) - physics , astrophysics , balmer series , white dwarf , roche lobe , brightness , symbiotic star , flux (metallurgy) , emission spectrum , equivalent width , astronomy , spectral line , stars , materials science , metallurgy
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 M V =−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.