Parallax of Galactic Cepheids from Spatially Scanning the Wide Field Camera 3 on the Hubble Space Telescope: The Case of SS Canis Majoris
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 μas, 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 18 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 μas, 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2016
- DOI:
- 10.3847/0004-637X/825/1/11
- arXiv:
- arXiv:1512.09371
- Bibcode:
- 2016ApJ...825...11C
- Keywords:
-
- cosmology: observations;
- distance scale;
- parallaxes;
- stars: individual: SS CMa;
- stars: variables: Cepheids;
- supernovae: general;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- Submitted to ApJ on December 30, 2015. Comments welcome. Replaced original version to fix latex errors that prevented tables to show