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arXiv · 1512.09371

Parallax of Galactic Cepheids from Spatially Scanning the Wide Field Camera 3 on the Hubble Space Telescope: The Case of SS Canis Majoris

Stefano Casertano·Adam G. Riess·Jay Anderson·Richard I. Anderson·J. Bradley Bowers·Kelsey I. Clubb·Aviv R. Cukierman·Alexei V. Filippenko·Melissa L. Graham·John W. MacKenty·Carl Melis·Brad E. Tucker·Gautam Upadhya
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Abstract

We present a high-precision measurement of the parallax for the 12-day Cepheid SS Canis Majoris, obtained via spatial scanning with the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). Spatial scanning enables astrometric measurements with a precision of 20-40 muas, an order of magnitude better than pointed observations. SS CMa is the second Cepheid targeted for parallax measurement with HST, and is the first of a sample of eighteen long-period >~ 10 days) Cepheids selected in order to improve the calibration of their period-luminosity relation and eventually permit a determination of the Hubble constant H_0 to better than 2%. The parallax of SS CMa is found to be 348 +/- 38 muas, corresponding to a distance of 2.9 +/- 0.3 kpc. We also present a refinement of the static geometric distortion of WFC3 obtained using spatial scanning observations of calibration fields, with a typical magnitude <~0.01 pixels on scales of 100 pixels.

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Stefano Casertano, Adam G. Riess, Jay Anderson, Richard I. Anderson, J. Bradley Bowers, Kelsey I. Clubb, Aviv R. Cukierman, Alexei V. Filippenko, Melissa L. Graham, John W. MacKenty, Carl Melis, Brad E. Tucker, Gautam Upadhya. 2016-01-01. Parallax of Galactic Cepheids from Spatially Scanning the Wide Field Camera 3 on the Hubble Space Telescope: The Case of SS Canis Majoris. https://doi.org/10.3847/0004-637x%2F825%2F1%2F11

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