@article{JaervinenHubrigIlyinetal.2017,
  author    = {Jaervinen, S. P. and Hubrig, Swetlana and Ilyin, Ilya and Shenar, Tomer and Schoeller, M.},
  title     = {A search for spectral variability in the highly magnetized O9.7 V star HD 54879},
  series = {Astronomische Nachrichten = Astronomical notes},
  volume    = {338},
  journal   = {Astronomische Nachrichten = Astronomical notes},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0004-6337},
  doi       = {10.1002/asna.201713402},
  pages     = {952 -- 958},
  year      = {2017},
  abstract  = {The O9.7 V star HD 54879 possesses the second strongest magnetic field among the single, magnetic, O-type stars. In contrast to other magnetic O-type stars, the chemical abundance analysis of HD 54879 indicated a rather normal optical spectrum without obvious element enhancements or depletions. Furthermore, spectral variability was detected only in lines partly formed in the magnetosphere. As this star shows such a deviate, almost nonvariable, spectral behavior, we performed a deeper analysis of its spectral variability on different timescales using all currently available HARPSpol and FORS 2 spectropolarimetric observations. The longitudinal magnetic field strengths measured at different epochs indicate the presence of variability possibly related to stellar rotation, but the current data do not allow us yet to identify the periodicity of the field variation. As spectropolarimetric observations obtained at different epochs consist of subexposures with different integration times, we investigated spectral variability on timescales of minutes. The detected level of variability in line profiles of different elements is rather low, between 0.2 and 1.7\%, depending on the integration time of the exposures and the considered element.},
  language  = {en}
}
@article{SchoellerHubrigIlyinetal.2011,
  author    = {Schoeller, M. and Hubrig, Swetlana and Ilyin, Ilya and Kharchenko, N. V. and Briquet, Maryline and Gonzalez, J. F. and Langer, Norbert and Oskinova, Lida},
  title     = {Magnetic field studies of massive main sequence stars},
  series = {Astronomische Nachrichten = Astronomical notes},
  volume    = {332},
  journal   = {Astronomische Nachrichten = Astronomical notes},
  number    = {9-10},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  organization    = {MAGORI Collaboration},
  issn      = {0004-6337},
  doi       = {10.1002/asna.201111606},
  pages     = {994 -- 997},
  year      = {2011},
  abstract  = {We report on the status of our spectropolarimetric observations of massive stars. During the last years, we have discovered magnetic fields in many objects of the upper main sequence, including Be stars, beta Cephei and Slowly Pulsating B stars, and a dozen O stars. Since the effects of those magnetic fields have been found to be substantial by recent models, we are looking into their impact on stellar rotation, pulsation, stellar winds, and chemical abundances. Accurate studies of the age, environment, and kinematic characteristics of the magnetic stars are also promising to give us new insight into the origin of the magnetic fields. Furthermore, longer time series of magnetic field measurements allow us to observe the temporal variability of the magnetic field and to deduce the stellar rotation period and the magnetic field geometry. Studies of the magnetic field in massive stars are indispensable to understand the conditions controlling the presence of those fields and their implications on the stellar physical parameters and evolution.},
  language  = {en}
}