paper

Confirmation of the DR2 parallax zero-point offset using asteroseismology and spectroscopy in the field

arXiv:1805.02650 · doi:10.3847/1538-4357/ab1f66

Abstract

We present an independent confirmation of the zero-point offset of Data Release 2 (DR2) parallaxes using asteroseismic data of evolved stars in the field. Using well-characterized red giant branch (RGB) stars from the APOKASC-2 catalogue we identify a astrometric pseudo-color ()- and -band magnitude-dependent zero-point offset of , in the sense that parallaxes are too small. The offset is found in high and low-extinction samples, as well as among both shell H-burning red giant stars and core He-burning red clump stars. We show that errors in the asteroseismic radius and temperature scales may be distinguished from errors in the parallax scale. We estimate systematic effects on the inferred global parallax offset, , due to radius and temperature systematics, as well as choices in bolometric correction and the adopted form for parallax spatial correlations. Because of possible spatially-correlated parallax errors, as discussed by the team, our parallax offset model is specific to the field, but broadly compatible with the magnitude- and color-dependent offset inferred by the team and several subsequent investigations using independent methods.

Accepted for publication in ApJ. Added Fig. 1 (comparison of literature estimates of zero-point); Fig. 3 (covariance of zero-point model parameters); & Fig. 7 (zero-point using alternate bolometric correction). Systematic uncertainty on zero-point now includes effects from asteroseismic radius, temperature, & bolometric correction, in addition to spatial correlation. 19 pages, 7 figures

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