MERLIN observations of bipolar outflow from HM Sagittae

S. P. S. Eyres, H.t. Kenny, R. J. Cohen, H. M. Lloyd, S. M. Dougherty, R. J. Davis, M. F. Bode

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MERLIN maps of HM Sagittae at 6-cm and 18-cm wavelengths are presented. At 6 cm, the inner nebula has been mapped at a resolution of 60 milli-arcsec (mas), revealing two parallel ridge structures to the north and south of a deep central minimum. In addition, these central features are surrounded by a complex, weak structure. The ridges and many of the weak features are correlated with ultraviolet (UV) structure observed with the Hubble Space Telescope (HST). The 18-cm map reveals elongated structure to the east and west of the stars position. There is strong evidence that the eastern and western edges of this extension are non-thermal. The E–W and N–S features are associated with components detected with optical spectroscopy. The radial velocities of these components suggest that the E–W features are a high-velocity bipolar outflow. We argue that the brightness temperature of ∼ 45000K for the N-S features results from shock heating by the outflow. The resulting expansion velocity, when compared with the observed proper motion, implies a distance of 3.2 kpc.

Original languageEnglish
Pages (from-to)317-323
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - 1 May 1995


  • binaries: symbiotic
  • circumstellar matter
  • stars: imaging
  • stars: individual: HM Sge
  • stars: late-type
  • radio continuum: stars


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