A geometrical 1% distance to the short-period binary Cepheid V1334 Cygni
Gallenne, A; Kervella, P; Evans, NR; et al.Proffitt, CR; Monnier, JD; Merand, A; Nelan, E; Winston, E; Pietrzynski, G; Schaefer, G; Gieren, W; Anderson, RI; Borgniet, S; Kraus, S; Roettenbacher, RM; Baron, F; Pilecki, B; Taormina, M; Graczyk, D; Mowlavi, N; Eyer, L
Date: 6 November 2018
Journal
Astrophysical Journal
Publisher
American Astronomical Society / IOP Publishing
Publisher DOI
Abstract
Cepheid stars play a considerable role as extragalactic distances indicators, thanks to the simple
empirical relation between their pulsation period and their luminosity. They overlap with that of
secondary distance indicators, such as Type Ia supernovae, whose distance scale is tied to Cepheid
luminosities. However, the Period–Luminosity ...
Cepheid stars play a considerable role as extragalactic distances indicators, thanks to the simple
empirical relation between their pulsation period and their luminosity. They overlap with that of
secondary distance indicators, such as Type Ia supernovae, whose distance scale is tied to Cepheid
luminosities. However, the Period–Luminosity (P-L) relation still lacks a calibration to better than 5 %.
Using an original combination of interferometric astrometry with optical and ultraviolet spectroscopy,
we measured the geometrical distance d = 720.35±7.84 pc of the 3.33 d period Cepheid V1334 Cyg with
an unprecedented accuracy of ±1 %, providing the most accurate distance for a Cepheid. Placing this
star in the P–L diagram provides an independent test of existing period-luminosity relations. We show
that the secondary star has a significant impact on the integrated magnitude, particularly at visible
wavelengths. Binarity in future high precision calibrations of the P–L relations is not negligible,
at least in the short-period regime. Subtracting the companion flux leaves V1334 Cyg in marginal
agreement with existing photometric-based P–L relations, indicating either an overall calibration bias
or a significant intrinsic dispersion at a few percent level. Our work also enabled us to determine the
dynamical masses of both components, M1 = 4.288±0.133 M (Cepheid) and M2 = 4.040±0.048 M
(companion), providing the most accurate masses for a Galactic binary Cepheid system
Physics and Astronomy
Faculty of Environment, Science and Economy
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