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Paper: Parallaxes with Hubble Space Telescope - How and Why We Do It
Volume: 338, Astrometry in the Age of the Next Generation of Large Telescopes
Page: 58
Authors: Benedict, G.F.; McArthur, B.E.
Abstract: Obtaining absolute parallaxes with Hubble Space Telescope is sort of like making sausage; a lot goes into it, some parts prettier than others. We have established a process whereby ANY information relevant to the final parallax result can be used. The impact of this information is weighted fairly by how well it is known. As an example we describe how we obtained an absolute parallax for three stars in the Pleiades, a somewhat contentious issue, given the discrepancies between the 800 lb (and extremely valuable!) gorilla of Astrometry (HIPPARCOS) and everybody else. For this result we included previously measure proper motions, multi-color photometry, and luminosity class estimates derived from reduced proper motion diagrams. Additionally, we constrained the parallax differences among the three Pleiades members by limiting the depth of the cluster. This depth was based on the angular size of the Pleiades and an assumption of spherical symmetry. We find pi(abs) = 7.43 +/- 0.17 milliseconds of arc, in excellent agreement with distances obtained through main sequence fitting.
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