Vetting galactic Leavitt law calibrators using radial velocities: On the variability, binarity, and possible parallax error of 19 long-period cepheids
- Department of Physics and Astronomy, The Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218 (United States)
- Space Telescope Science Institute, 3700 San Martin Dr, Baltimore, MD 21218 (United States)
- Center for Astrophysics and Space Sciences, University of California, San Diego, CA 92093 (United States)
- Département d’Astronomie, Université de Genève, 51 Ch. des Maillettes, 1290 Sauverny (Switzerland)
We investigate the radial velocity (RV) variability and spectroscopic binarity of 19 Galactic long-period (P{sub puls} ≳ 10 days) classical Cepheid variable stars whose trigonometric parallaxes are being measured using the Hubble Space Telescope and Gaia. Our primary objective is to constrain possible parallax error due to undetected orbital motion. Using over 1600 high-precision RVs measured between 2011 and 2016, we find no indication of orbital motion on ≲5 year timescales for 18 Cepheids and determine upper limits on allowed configurations for a range of input orbital periods. The results constrain the unsigned parallax error due to orbital motion to <2% for 16 stars, and <4% for 18. We improve the orbital solution of the known binary YZ Carinae and show that the astrometric model must take into account orbital motion to avoid significant error (∼±100 μarcsec). We further investigate long-timescale (P{sub orb} > 10 years) variations in pulsation-averaged velocity v {sub γ} via a template fitting approach using both new and literature RVs. We discover the spectroscopic binarity of XZ Car and CD Cyg, find first tentative evidence for AQ Car, and reveal KN Cen’s orbital signature. Further (mostly tentative) evidence of time-variable v {sub γ} is found for SS CMa, VY Car, SZ Cyg, and X Pup. We briefly discuss considerations regarding a vetting process of Galactic Leavitt law calibrators and show that light contributions by companions are insignificant for most distance scale applications.
- OSTI ID:
- 22872471
- Journal Information:
- Astrophysical Journal, Supplement Series, Vol. 226, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0067-0049
- Country of Publication:
- United States
- Language:
- English
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