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- Volume 80 - Année 2011
- Two New LBV Candidates in the M 33 Galaxy
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Two New LBV Candidates in the M 33 Galaxy
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Abstract
We present two new luminous blue variable (LBV) candidate stars discovered in M 33. We identified these stars (Valeev et al. 2010a, b) as massive star candidates at the final stages of evolution. The candidates were selected from the Massey et al. (2006) catalog based on the following criteria: emission in Halpha, V < 18.m 5 and 0.m 35 < (B−V) < 1.m 2 (presumably reddened early stars). Based on our spectroscopy of the stars, we estimated their main parameters. Object N4 5901 has a bolometric luminosity log(L/Lo) = 6.0 – 6.2 with the value of interstellar extinction AV = 2.3±0.1. The temperature of the star’s photosphere is T* ~ 13000 − 15000 K, its probable mass is M ~ 60–80 Mo. The infrared excess in N 45901 corresponds to the emission of warm dust with a temperature Twarm ~ 1000 K. the bolometric luminosity of the second object, N125093, is log(L/Lo) = 6.3 – 6.6, the value of interstellar extinction is AV = 2.75 ± 0.15. Its photosphere’s temperature is T* ~ 13000 − 16000 K, the initial mass is M ~ 90-120 Mo. The infrared excess in N125093 amounts to 5–6% of the bolometric luminosity. Its spectral energy distribution reveals two thermal components with temperatures Twarm ~ 1000K and Tcold ~ 480 K. The [Ca II] lambda lambda 7291, 7323 lines, observed in LBV-like stars Var A and N 93351 in M33, are also present in the spectrum of N 125093. The high bolometric luminosities of these stars and broad Halpha emissions allow classifying the studied objects as LBV candidates.
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Acerca de: O. N. Sholukhova
Special Astrophysical Observatory of the Russian AS, Nizhnij Arkhyz, Russia
Acerca de: A. F. Valeev
Special Astrophysical Observatory of the Russian AS, Nizhnij Arkhyz, Russia
Acerca de: S. N Fabrika
Special Astrophysical Observatory of the Russian AS, Nizhnij Arkhyz, Russia