Positions of 127 Hyads and 6-cm observations of 320 Hyads
Publications of the Astronomical Society of the Pacific
Accurate positions are given for 127 Hyades cluster stars which previously had only approximate positions known. The fields of 320 Hyads, including 55 X-ray stars, were observed with the VLA to a 6-cm detection level of approximately 0.5 mJy. There were no detections. Key words : star clusters-radio stars-astronomy Recently, Upgren and Weis (see numerous references) performed a lengthy photometric study of all probable Hyades cluster members and subsequent careful evaluation of that membership,
... resulting in the most complete well-determined cluster membership to date. With the ultimate objective of measuring the trigonometric parallax of some Hyads at radio frequencies, using the astrometric potential of the VLA, we proceeded to survey 320 of these members at 6-cm. Unfortunately, only approximate positions were known for 127 of the stars. Since for source identification purposes we required positions to within two or three arc seconds, we measured positions on the Palomar Sky Survey blue prints using the two-coordinate automated Mann measuring engine at the VLA site. The resulting accurate positions of these stars, with reference to SAO positions, are listed in Table I . While the errors vary somewhat, depending on the availability of SAO reference stars and on how far the image lies from the print center, a typical mean error is about one arc second in either coordinate. We can also regrettably report that only one Hyad (V471 Tauri -BD +16°516 = GH7-23) was detected, but that this appears to have been merely a transient 1 mJy flare, not continuum emission. Included in our observing list were the 55 known X-ray bright Hyads. Our detection level was approximately 0.5 mJy. We are most grateful to Drs. Upgren and Weis for kindly making available their master list of Hyades members, including the identification cross reference given in Table I . We also thank Drs. B. Stern and M.-C. Zolcinski for privately communicating the known X-ray bright Hyads.