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New LBV Star Discovered in the Galaxy - a Twin of the Famous LBV P Cygni

Russian version  

    Luminous blue variable (LBV) stars are the most massive stars with 40-120 solar masses, which are passing the short stage of evolution losing their hydrogen envelopes before exploding as Supernovae. These are extremely rare objects, only about a dozen of the most massive LBVs are known in the Galaxy. The theory predicts that there should be several dozen of such objects in the Galaxy. But all still undiscovered LBVs are hidden from us by the dust absorption. Astrophysicist from Sternberg Institute V.V.Gvaramadze studied infrared images surveyed by the space Spitzer Observatory to search for hidden LBVs and made a list of candidates which later were studied with the BTA.
    In the spectral observations of stars with infrared circular nebulae, found in the Spitzer survey (24 microns), a new LBV star in the Galaxy was discovered. It was named MN112. The spectrum of MN112 is almost identical to the famous LBV P Cygni. The star P Cygni itself was one of the brightest stars in the sky 400 years ago. An archive search showed that the brightness of MN112 in the I-band grew by 0.4 magnitudes over the past 17 years. The absorption of light to MN112 is about 9 magnitudes in the V-band. The differences between MN112 and P Cygni: MN112 bolometric luminosity is somewhat higher (and therefore its mass is greater), temperature is also slightly higher (for precise temperature measurements further modelling studies are required), the wind velocity is 2 times higher and amounts to around 400km/s.
SAO: S.N.Fabrika, O.N.Sholukhova
SAI: V.V.Gvaramadze, A.M.Cherepashchuk, L.N.Berdnikov, A.V.Zharova
SAAO: A.Y. Kniazev
(Gvaramadze et al., MNRAS, 2010, accepted for publication)

Contact - S.N.Fabrika

Fig.1. Image of the ring nebula around MN112 (Spitzer MIPS, 24 microns)

Fig.2. MN112 spectra (BTA, SCORPIO and Calar Alto, TWIN) with an identification of principal lines