OH Masers in U Herculis (HD 148206)

https://www.nrao.edu/archives/plugins/Dropbox/files/uher6eps.jpg

Description

Circumstellar OH masers are found in the envelope around late type stars. The star itself is obscured by the shell. However, the most blue-shifted spot is thought to be amplified emission from the underlying star. This maser spot would then be a bright beacon, necessarily fixed on the stellar position. Using the maser we can thus trace the stellar trajectory. Using phase referenced VLBA observations of U Her we have obtained very accurate positions for the maser spots in a period of over 4 years. This allows us to determine proper motion and even parallax of the star. The pictures above show the motion of the most blue-shifted maser spot over this 4 year period. The proper motion can clearly be seen. We have also compared the positions of the spots with the optical position determined by the Hipparcos sattelite with unprecedented accuracy (U Her is still faintly visible in the optical). As predicted by the theory the position of the most blue-shifted maser spot matches the Hipparcos position to within 15 mas.

Creator

Legacy Astronomical Images

Rights

NRAO/AUI/NSF does not hold full copyright for this image. Contact the archivist for details.

Type

Legacy Astronomical Image

Object Name

HD148206

Photo Credit

H.J. van Langevelde and W. Vlemmings

Investigators

H.J. van Langevelde, W. Vlemmings

Telescope

Very Long Baseline Array (VLBA)

Observation Date

1999-00-00

Type of Observation

continuum

Band

L

Wavelength

20 cm

Frequency

1.4 GHz

Center of Image

RA 16:25:47.470, Dec: 18:53:32.900 (J2000)

Series

Galactic Sources Series

Unit

Stars Unit

Citation

Legacy Astronomical Images, “OH Masers in U Herculis (HD 148206),” NRAO Archives, accessed December 3, 2021, https://www.nrao.edu/archives/items/show/33504.