The First DIRECT Distance Determination to a Detached Eclipsing Binary in M33

By Alceste Z. Bonanos, Krzysztof Zbigniew Stanek, R. Kudritzki, Lucas Macri, D. Sasselov, J. Kaluzny, P. Stetson, D. Bersier, F. Bresolin, Thomas Matheson and 5 more. 2006

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We present the first direct distance determination to a detached eclipsing binary in M33, which was found by the DIRECT Project. Located in the OB 66 association at coordinates (α, δ) = (01h33m46.ˢ17, + 30°44′39.″9) for J2000.0, it was one of the most suitable detached eclipsing binaries found by DIRECT for distance determination, given its apparent magnitude and orbital period. We obtained follow-up BV time-series photometry, JHKs photometry, and optical spectroscopy from which we determined the parameters of the system. It contains two O7 main-sequence stars, with masses of 33.4 ± 3.5 and 30.0 ± 3.3 M☉ and radii of 12.3 ± 0.4 and 8.8 ± 0.3 R☉, respectively. We derive temperatures of 37,000 ± 1500 and 35,600 ± 1500 K. Using BVRJHKs photometry for the flux calibration, we obtain a distance modulus of 24.92 ± 0.12 mag (964 ± 54 kpc), which is ~0.3 mag longer than the Key Project distance to M33. We discuss the implications of our result and the importance of establishing M33 as an independent rung on the cosmological distance ladder.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/808994112715787a92fd78e5d750e5a5839adfed

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Citations in the corpus

COSMICFLOWS-2: THE DATA (2013, background): “Some eclipsing binary measures are becoming available (Bonanos et al. 2006).”
SPITZER SAGE INFRARED PHOTOMETRY OF MASSIVE STARS IN THE LARGE MAGELLANIC CLOUD (2009, background): “′′7, which corresponds to 0.4 pc in the LMC (at a distance of 48.1 kpc; Macri et al. 2006), and 8 pc in M33 (at a distance of 964 kpc; Bonanos et al. 2006), while typical OB associations have sizes of tens of parsecs (but half-light radii of several parsecs), and young massive clusters can have…”
KEPLER ECLIPSING BINARY STARS. VII. THE CATALOG OF ECLIPSING BINARIES FOUND IN THE ENTIRE KEPLER DATA SET (2015, background): “Indeed, EBs are becoming widely used to determine distances to the Magellanic Clouds, M31, and M33 (Guinan et al. 1998; Wyithe & Wilson 2001, 2002; Ribas et al. 2002; Bonanos et al. 2003, 2006; Hilditch et al. 2005; North et al. 2010).”
A NEW CLASS OF LUMINOUS TRANSIENTS AND A FIRST CENSUS OF THEIR MASSIVE STELLAR PROGENITORS (2008, methodology): “In addition, Bonanos et al. (2006) also quote an average reddening correction of 0.1 mag to massive stars for M33.”
KEPLER ECLIPSING BINARY STARS. I. CATALOG AND PRINCIPAL CHARACTERIZATION OF 1879 ECLIPSING BINARIES IN THE FIRST DATA RELEASE (2010, background): “Indeed, EBs are becoming widely used to determine distances to the Magellanic Clouds, M31, and M33 (Paczynski & Sasselov 1997; Paczynski & Pojmanski 2000; Guinan et al. 1998; Ribas et al. 2002; Wyithe & Wilson 2001, 2002; Bonanos et al. 2003, 2006; North et al. 2010).”
THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY (2012, background): “Somewhat surprisingly, the distance to M31 remained largely uncontroversial in the last two decades, unlike for the other galaxies in the Local Group, be it the Large Magellanic Cloud (e.g., Macri et al. 2006; van Leeuwen et al. 2007) or M33 (e.g., Bonanos et al. 2006; Scowcroft et al. 2009).”