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Session 14 - Various Stellar Surveys.
Display session, Wednesday, January 07
Exhibit Hall,
Most objects studied by radio astronomers today are the unexpected discoveries of early surveys. Unfortunately, very few stars were found, so nearly all known radio stars have been detected by sensitive observations directed at small samples of stars thought likely to be radio emitters. Such observations are productive but biased against discovering unknown, unexpected, or intrinsically rare objects.
We have used the new NRAO VLA Sky Survey (NVSS) to identify unbiased samples of the brightest radio stars in the Ømega \approx 10 sr of sky with \delta > -40^\circ. Our principal sample consists of all stars brighter than V = 10.5, the completeness limit of the Tycho catalog, and stronger than 5 mJy at 1.4 GHz. Additional samples of X-ray stars from the ROSAT All-Sky Survey, far-infrared stars from the IRAS Faint Source Catalog, and optically selected emission-line stars, chromospherically active binaries, cataclysmic variables, white dwarfs, and stars within 25 pc were associated with NVSS sources stronger than 2.5 mJy.
The NVSS identification candidates were reobserved by the VLA on 1997 September 27 in Stokes I, Q, U, and V with 45'' resolution at 1.4 GHz and 8'' resolution at 8.4 GHz. The 1.4 GHz observations match the NVSS resolution and indicate which sources have varied in total intensity and linear polarization. The nearly simultaneous 1.4 and 8.4 GHz observations determine their radio spectral indices, and the high-resolution 8.4 GHz data were used to confirm or reject uncertain candidates on the basis of position coincidence.
At least 50 radio stars were found, most for the first time. They exhibit a range of radio spectra, angular sizes, and polarizations indicating a variety of emission mechanisms. We are following these stars with high-resolution optical spectroscopy.
