@misc{GvaramadzeKniazevMiroshnichenkoetal.2012,
  author    = {Gvaramadze, V. V. and Kniazev, A. Y. and Miroshnichenko, A. S. and Berdnikov, Leonid N. and Langer, N. and Stringfellow, G. S. and Todt, Helge Tobias and Hamann, Wolf-Rainer and Grebel, E. K. and Buckley, D. and Crause, L. and Crawford, S. and Gulbis, A. and Hettlage, C. and Hooper, E. and Husser, T. -O. and Kotze, P. and Loaring, N. and Nordsieck, K. H. and O'Donoghue, D. and Pickering, T. and Potter, S. and Colmenero, E. Romero and Vaisanen, P. and Williams, T. and Wolf, M. and Reichart, D. E. and Ivarsen, K. M. and Haislip, J. B. and Nysewander, M. C. and LaCluyze, A. P.},
  title     = {Discovery of two new Galactic candidate luminous blue variables with Wide-field Infrared Survey Explorer},
  series = {Monthly notices of the Royal Astronomical Society},
  volume    = {421},
  journal   = {Monthly notices of the Royal Astronomical Society},
  number    = {4},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0035-8711},
  doi       = {10.1111/j.1365-2966.2012.20556.x},
  pages     = {3325 -- 3337},
  year      = {2012},
  abstract  = {We report the discovery of two new Galactic candidate luminous blue variable (LBV) stars via detection of circular shells (typical of confirmed and candidate LBVs) and follow-up spectroscopy of their central stars. The shells were detected at 22 mu m in the archival data of the Mid-Infrared All Sky Survey carried out with the Wide-field Infrared Survey Explorer (WISE). Follow-up optical spectroscopy of the central stars of the shells conducted with the renewed Southern African Large Telescope (SALT) showed that their spectra are very similar to those of the well-known LBVs P Cygni and AG Car, and the recently discovered candidate LBV MN112, which implies the LBV classification for these stars as well. The LBV classification of both stars is supported by detection of their significant photometric variability: one of them brightened in the R and I bands by 0.68 +/- 0.10 and 0.61 +/- 0.04 mag, respectively, during the last 1318 years, while the second one (known as Hen 3-1383) varies its B, V, R, I and Ks brightnesses by similar or equal to 0.50.9 mag on time-scales from 10 d to decades. We also found significant changes in the spectrum of Hen 3-1383 on a time-scale of similar or equal to 3 months, which provides additional support for the LBV classification of this star. Further spectrophotometric monitoring of both stars is required to firmly prove their LBV status. We discuss a connection between the location of massive stars in the field and their fast rotation, and suggest that the LBV activity of the newly discovered candidate LBVs might be directly related to their possible runaway status.},
  language  = {en}
}
@article{TodtKniazevGvaramadzeetal.2013,
  author    = {Todt, Helge Tobias and Kniazev, A. Y. and Gvaramadze, V. V. and Hamann, Wolf-Rainer and Buckley, D. and Crause, L. and Crawford, S. M. and Gulbis, A. A. S. and Hettlage, C. and Hooper, E. and Husser, T. -O. and Kotze, P. and Loaring, N. and Nordsieck, K. H. and O'Donoghue, D. and Pickering, T. and Potter, S. and Romero-Colmenero, E. and Vaisanen, P. and Williams, T. and Wolf, M.},
  title     = {Abell 48-a rare WN-type central star of a planetary nebula},
  series = {Monthly notices of the Royal Astronomical Society},
  volume    = {430},
  journal   = {Monthly notices of the Royal Astronomical Society},
  number    = {3},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0035-8711},
  doi       = {10.1093/mnras/stt056},
  pages     = {2302 -- 2312},
  year      = {2013},
  abstract  = {A considerable fraction of the central stars of planetary nebulae (CSPNe) are hydrogen-deficient. Almost all of these H-deficient central stars (CSs) display spectra with strong carbon and helium lines. Most of them exhibit emission-line spectra resembling those of massive WC stars. Therefore these stars are classed as CSPNe of spectral type [WC]. Recently, quantitative spectral analysis of two emission-line CSs, PB 8 and IC 4663, revealed that these stars do not belong to the [WC] class. Instead PB 8 has been classified as [WN/WC] type and IC 4663 as [WN] type. In this work we report the spectroscopic identification of another rare [WN] star, the CS of Abell 48. We performed a spectral analysis of Abell 48 with the Potsdam Wolf-Rayet (PoWR) models for expanding atmospheres. We find that the expanding atmosphere of Abell 48 is mainly composed of helium (85 per cent by mass), hydrogen (10 per cent) and nitrogen (5 per cent). The residual hydrogen and the enhanced nitrogen abundance make this object different from the other [WN] star IC 4663. We discuss the possible origin of this atmospheric composition.},
  language  = {en}
}