Improving RR Lyrae Distances and Luminosities Using JMAPS Observations

Details Improving RR Lyrae Distances and Luminosities Using JMAPS Observations Improving RR Lyrae Distances and Luminosities Using JMAPS Observations

Jan 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21541710e&link_type=abstract

American Astronomical Society, AAS Meeting #215, #417.10; Bulletin of the American Astronomical Society, Vol. 42, p.272

Astronomy and Astrophysics

Astronomy

Scientific paper

Trigonometric parallax is the only direct means of measuring stellar distances but is only effective within a limited distance. For stars too distant for the determination of accurate parallaxes, indirect methods, such as standard candles, are used. RR Lyrae and Cepheid variable stars are used as standard candles, because their luminosities can be inferred from their periods. The quality of such a period- luminosity relationship depends on accurate distances to a sufficient number of stars. However, only a few RR Lyrae parallactic distances are available. Of these distances, Hipparcos-2 parallaxes have an average error >2 mas. JMAPS will measure parallaxes accurate to 1 mas along with 1% photometry for all stars brighter than 12 mag (I-band). These observations will include at least 178 known RR Lyrae, nearly half of which are thought to lie within 1 kpc. In addition, JMAPS will have the advantage of a near-infrared band, which may reduce the metallicity dependence of the RR Lyrae period-luminosity relationship.
The JMAPS observing plan calls for at least 72 observations of each star during the 3 year mission. While this plan is appropriate for the required milliarcsecond astrometry, it may not result in the best possible light curves for variable stars. This study evaluates the effectiveness of such observations of RR Lyrae and considers options to optimize the light curves from which periods and luminosities would be determined. Through improved astrometry and photometry from JMAPS, the RR Lyrae period-luminosity relationship will be refined and our overall knowledge of cosmic distance scale will be improved.

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