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The Orbit of 16 Cygni AB

Marcy, Geoffrey W.; Hauser, Heather M.

The high orbital eccentricity of the planet around 16 Cygni B may have been induced by the companion star, 16 Cygni A, but only if the stellar binary has sufficiently small periastron distance. The long period of the stellar binary, ~3x10^4 yr, implies that less than 1% of the orbit has transpired since its first astrometric measurements in 1830. …

The CaII-M_v Correlation (Wilson-Bappu Effect) Calibrated by HIPPARCOS Parallaxes

Wallerstein, George; Machado-Pelaez, Laura; Gonzalez, Guillermo

We have used Hipparcos parallaxes to derive absolute visual magnitudes of G, K, and M stars with Ca II emission line widths previously measured by O. C. Wilson. A linear relationship similar to the one derived originally by Wilson & Bappu and improved by Lutz & Kelker was found from M_v=+7 to -2. For stars brighter than M_v=-2 a substantia…

Adaptive Optics Observations of Arcturus using the Mount Wilson 100 Inch Telescope

Mason, Brian D.; ten Brummelaar, Theo A.; Turner, Nils H.

Upon inspection of the multiple-star results in the Hipparcos catalog, the flag for entry number 69673 particularly stands out; it is Arcturus, for which no companion has been reported previously. The Hipparcos companion is reported to be at a separation of 0.255"+/-0.039" with a magnitude difference in a broadband filter (peaked near 460 nm) of 3…

The Use of Gamma-Ray Bursts as Direction and Time Markers in SETI Strategies

Corbet, Robin H. D.

When transmitting a signal over a large distance, it is more efficient to send a brief beamed signal than a continuous omnidirectional transmission, but this requires that the receiver knows where and when to look for the transmission. For SETI, the use of various natural phenomena has previously been suggested to achieve the desired synchronizati…