http://bear.ras.ucalgary.ca/abstracts/1991/1991.html (Einblicke ins Internet, ~06/1995)
Radio variability of Be stars
DOUGHERTY, S. M., TAYLOR, A. R., WATERS, L. B. F. M.
Astronomy and Astrophysics , vol. 248, no. 1, Aug. 1991, p. 175-178. Research supported by NSERC.
Abstract: New multifrequency radio observations of six Be stars previously detected at 2 cm are presented. These observations were obtained to determine the outer structure of the circumstellar winds from the radio spectral indices and to search for radio variability. The radio spectral indices are all positive which provides conclusive evidence that the far-IR, millimeter and radio emission from Be stars arise from thermal radiation from ionized gas. Also, the radio spectral indices of four of the stars are in good agreement with spectral indices derived from millimeter and previous 2 cm observations, indicating that there is no significant change in the structure of the circumstellar material between the submillimeter-millimeter turnover and radio wavelengths. However, the radio spectral indices derived for beta Mon A and EW Lac, based on multiepoch data, are greater than +2.0, the maximum for thermal radio emission. This may result from an additional turnover at radio wavelengths or variability in the radio emission.
GT2318 + 620, a variable Galactic source with a radio jet
TAYLOR, A. R., GREGORY, P. C., DURIC, N., TSUTSUMI, T.
Nature , vol. 351, June 13, 1991, p. 547-549. NSERC-supported research.
Abstract: Neutral hydrogen absorption toward GT2318 + 620 is reported which indicates that it is a Galactic object at a distance of 3-6 kpc. A high-resolution radio image of the source is also presented which reveals an unresolved core with a jetlike feature extending on either side. GT2318 + 620 is coincident with a star of about 20th magnitude, and it is suggested that it is a radio-emitting low-mass X-ray binary (LMXB). The radio luminosity of GT2318 + 620 is markedly higher than that of Sco X-1, the only other LMXB to show a radio jet. In its radio brightness it resembles SS433, which is remarkable for its relativistic jet motion on arcsec scales, thought to result from accretion onto a collapsed stellar object.
The structure of circumstellar discs of Be stars - Millimeter observations
WATERS, L. B. F., MARLBOROUGH, J. M., VAN DER VEEN, W. E. C., TAYLOR, A. R., DOUGHERTY, S. M.
Astronomy and Astrophysics , vol. 244, no. 1, April 1991, p. 120-130. NSERC-supported research.
Abstract: Millimeter-wave observations of six bright classical Be stars were made with the James Clerk Maxwell Telescope. All stars exhibit an mm-cm spectral index that is steeper than the IRAS (12-60 micron) spectral index, indicating a turnover in the continuum energy distribution. It is suggested that this turnover may be caused by a change in the geometry of the disk or by an additional outward acceleration of the material at a large distance from the star.
AG Pegasi - A multishell radio source
KENNY, H. T., TAYLOR, A. R., SEAQUIST, E. R.
Astrophysical Journal, Part 1 , vol. 366, Jan. 10, 1991, p. 549-559.
Abstract Not Available
Near-IR observations of 101 Be stars
DOUGHERTY, S. M., TAYLOR, A. R., CLARK, T. A.
Astronomical Journal , vol. 102, Nov. 1991, p. 1753-1765. Research supported by NSERC.
Abstract: Observations of 101 Be stars taken over a two year period in the near-IR between 1 and 5 microns are presented and discussed. The near-IR color excess of all program stars is derived, and found to increase with wavelength for all these stars. The fraction of stars with color excess doubles between 1.25 and 3.6 microns. There appears to be an upper limit to the magnitude of the color excess as a function of stellar type, with early-type stars having a higher upper limit than later spectral types. No correlation of the presence or magnitude of color excess with projected rotational velocity is evident. The spectral index of the excess emission spectra is calculated for stars having color excess. On average, the spectral index through the near-IR and far-IR IRAS wavelength regimes is constant. There is evidence that some stars have excess emission with spectral index values outside the range expected for free-free and bound-free emission. This is attributed to either dust emission or the effect of absorption of photospheric emission by cool circumstellar material along the line of sight to the star.
Papers Published in Conference Proceedings
The Cosmic Microwave Background and the Radio Schmidt
Taylor, A.R.
in Proceeding of the Radio Schmidt Workshop,
ed. T. Landecker. pp. 193-196, 1991 (invited).
Papers presented at conferences (not included in conference
proceedings)
JCMT Observations of AGB Stars and Planetary Nebulae
Taylor, A.R.
1991 Canadian Astronomical Society Meeting, Toronto (invited)
VLBI Observations of the X-ray Binary Star LSI+61 303
Taylor, A.R. and Kenny, H.T.
1991 Canadian Astronomical Society Meeting, Toronto
Sub-millimeter Wavelength Observations of Symbiotic Stars
Seaquist, E.R. and Taylor, A.R.
1991 Canadian Astronomical Society Meeting, Toronto.
New Supernova Remnants from the WSRT 327MHz Galactic Plane Survey
Wallace, B.J., Taylor, A.R.
1991 Canadian Astronomical Society Meeting, Toronto.
Technical Reports
An Study of the Imaging Potential of the Radioastron Space-VLBI Mission
Taylor, A.R.
1991 commissioned report to the Canadian Space Agency.
Prepared by
Glen Young;
young@bear.ras.ucalgary.ca