[Previous] | [Session 42] | [Next]
B.D. Mason (U.S. Naval Observatory), T.J. Henry (Georgia State University), D.R. Soderblom (Space Telescope Science Institute), W.I. Hartkopf (U.S. Naval Observatory)
Duplicity surveys were made of four samples of nearby solar-type stars, segregated by chromospheric activity, were made to determine their multiplicity fraction and to investigate the relationship between multiplicity and age. This work is an expansion of a survey presented in Mason et al.\ (1998), however, the sample size has been increased by over an order of magnitude to give greater confidence to the results. The initial sample of nearby G dwarf stars was selected by sorting objects in the Hipparcos Catalogue (ESA 1997) based on color (0.5 < B-V < 1.0) and distance (\pi > 20 mas, i.e., d < 50pc). Of the 3420 targets, 3125 were investigated, 12% by utilizing archival speckle and the remained in four dedicated speckle runs in 2001 with NOAO telescopes.
Because chromospheric emission in solar-type stars in known to decline with advancing age, substantial samples of stars with known chromospheric emission can be used to study stellar multiplicity over a wide range of ages without taking into account the coeval nature of clusters. Given this known link, 2324 have had their chromospheric activity (HK emission) determined by Soderblom and collaborators using methods described in Henry et al.\ (1996).
Incorporating literature data allows us to expand our search regime to 5\farcs0 and \DeltaV<~3. While the number of systems classified as very active (N = 45) or very inactive (N = 102) is small, the overall result is a compelling relationship, possibly indicative of some mechanism disrupting binaries as they age. Over the detectable regime, the multiplicity fraction for very active stars is 17.8±6.3%, for active (N = 947) stars is 9.8±1.0%, for inactive (N = 1230) stars is 7.1±0.8% and for very inactive stars is 2.9±1.7%. When grouped in two bins, the difference (3.4±1.2%) corresponds to a confidence of 2.8\sigma.
[Previous] | [Session 42] | [Next]
Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.