VLBI Observations of OH stars: S Persei

M. R W Masheder, H. J. Van Langevelde, A. M S Richards, L. Greenhill, M. D. Gray

    Research output: Contribution to journalArticlepeer-review


    The masers in three stars, S Per, OH53.6-0.2 and VXSgr, were observed in the main lines of OH at λ18 cm in March 1997 with a VLBI array consisting of 6 EVN antennas and 3 in the USA. Both S Per and VX Sgr were detected on transatlantic baselines, showing that at least some of the maser spots are very compact with sizes less than around 2 mas. The observations confirm that in S Per there is main line OH emission close to star at a similar distance (≈ 100 AU) as the H2O shell. The most blue-shifted emission comes from the centre of the object suggesting radial amplification of the maser radiation, whilst most of the remainder comes from a thick shell, some 100 AU from the star. This contrasts with the 1612 MHz OH emission that comes from an outer shell some 1000 AU from the star. Estimates of the magnetic fields in the shell from Zeeman pairs in S Per show fields of a few hundred nT.
    Original languageEnglish
    Pages (from-to)563-567
    Number of pages4
    JournalNew Astronomy Reviews
    Issue number8-10
    Publication statusPublished - Nov 1999


    • 97.10.Fy
    • 97.10.Me
    • 97.20.Pm
    • Circumstellar matter: individual (S Persei)
    • Radio lines: stars
    • Stars: AGB and post-AGB


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