68 research outputs found
A new Luminous Variable in M33
We present a new luminous star in M33 located in the nuclear region. The star
shows strong FeII and [FeII] forest, hydrogen emissions in the spectrum, as
well as nebular lines. TiII and SiII lines were detected in absorption, their
radial velocity shifted by ~ -30km/s relative to emission lines. The star is
variable over seven years with 0.5 mag variations over a year. We studied its
spectral energy distribution together with five confirmed Luminous Blue
Variables and Var A in M33 using homogeneous data and methods. We found the
star's bolometric luminosity to be log(L/Lsun)~6.27, a surface temperature of
T~16000K and black body temperatures of two dust components of T~900 and 420K.
The new star has properties intermediate between the LBVs and VarA (probable
cool hypergiant). In the same time it has a hot photosphere, LBV-like
luminosity and an extensive circumstellar material (strong [CaII] lines). In
these seven luminous variables in M33 we find the total range of the hot
component luminosities is 1.0 dex, but that of the dust componets is 2.0 dex.
We conclude that the dust phenomenon in the luminous variables is temporary and
variable, and that dust activity may follow strong eruptions.Comment: 5 pages, 6 figures; MNRAS Letter accepte
Modeling spectra of MN112
MN112 is the Galactic luminous blue variable (LBV) candidate with
circumstellar nebula. P Cygni is the first discovered LBV, which was recorded
during major eruptions in the 17th century. The stars have similar spectra with
strong emission hydrogen lines, He I, N II, Si II, and Fe III lines. We present
results of the spectroscopic analysis and modeling of MN112 spectra. We
obtained main stellar parameters and chemical abundances of MN112 and compared
them with those of P Cygni. Atmosphere models were calculated using non-LTE
radiative transfer code CMFGEN. We have used spectra of MN112 obtained with the
3.5-m telescope at the Observatory of Calar Alto and 3.5-m ARC telescope at the
Apache Point Observatory. P Cygni spectra were taken with the 6-m BTA
telescope. We have found the best-fit of the observed spectrum with the model
at temperature K, clumping-corrected mass-loss rate
, filling-factor
, luminosity for MN112. The ratio of
helium to hydrogen He/H is 0.27 (by the number of atoms) with nitrogen
overabundance () and the underabundance of carbon
()
Spectral analysis of lbv stars in m31: Af and and Var 15
Copyright Β© International Astronomical Union 2015. We study spectra of two bona fide LBV stars in M31: AF And and Var 15. The spectra were obtained with the 6-m telescope (Russia) from 2005 to 2012. The model spectra were calculated with the CMFGEN code. We have not found strong changes in the spectra of the LBV stars in that time interval, however a certain variability has been detected. We estimate the star and wind parameters, such as luminosity, temperature, raduis, mass loss rate, escape velocity, hydrogen content, and reddening. We study the stars on the Hertzsprung-Russell diagram and find their initial masses using evolutionary tracks by Meynet et al. (1994)
Search for LBV Candidates in the M33 Galaxy
A total of 185 luminous blue variable (LBV) candidates with V < 18.5 and B-V
< 0.35 are selected based on the photometrical Survey of Local Group Galaxies
made by P. Massey et al. 2006. The candidates were selected using aperture
photometry of H-alpha images. The primary selection criterion is that the
prospective candidate should be a blue star with H-aplha emission. In order not
to miss appreciably reddened LBV candidates, we compose an additional list of
25 presumably reddened (0.35 < B-V < 1.2, V < 18.5) emission star candidates. A
comparison with the list of known variables in the M33 galaxy showed 29% of our
selected candidates to be photometrically variable. We also find our list to
agree well with the lists of emission-line objects obtained in earlier papers
using different methods.Comment: 6 figure
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