First Results from the CHARA Array. VII. Long-Baseline Interferometric Measurements of Vega Consistent with a Pole-On, Rapidly Rotating Star

By J. Aufdenberg, A. Mérand, V. C. Foresto, O. Absil, E. D. Folco, Pierre Kervella, S. Ridgway, D. Berger, T. T. ten Brummelaar, H. Mcalister and 3 more. 2006

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We have obtained high-precision interferometric measurements of Vega with the CHARA Array and FLUOR beam combiner in the K′ band at projected baselines between 103 and 273 m. The measured visibility amplitudes beyond the first lobe are significantly weaker than expected for a slowly rotating star characterized by a single effective temperature and surface gravity. Our measurements, when compared to synthetic visibilities and synthetic spectrophotometry from a Roche-von Zeipel gravity-darkened model atmosphere, provide strong evidence for the model of Vega as a rapidly rotating star viewed very nearly pole-on. Our best-fitting model indicates that Vega is rotating at ~91% of its angular break-up rate with an equatorial velocity of 275 km s-1. Together with the measured v sin i, this velocity yields an inclination for the rotation axis of 5°. For this model the pole-to-equator effective temperature difference is ~2250 K, a value much larger than previously derived from spectral line analyses. A polar effective temperature of 10,150 K is derived from a fit to ultraviolet and optical spectrophotometry. The synthetic and observed spectral energy distributions are in reasonable agreement longward of 140 nm, where they agree to 5% or better. Shortward of 140 nm, the model is up to 10 times brighter than observed. The model has a luminosity of ~37 L☉, a value 35% lower than Vega's apparent luminosity based on its bolometric flux and parallax, assuming a slowly rotating star. Our model predicts the spectral energy distribution of Vega as viewed from its equatorial plane, and it may be employed in radiative models for the surrounding debris disk.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/958bb34fb42f264a248c878b5430a603a799328d

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1. S. Kenyon
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Citations in the corpus

• Accurate fundamental parameters for lower main‐sequence stars (2006, unknown): “Recent work by Gulliver, Hill & Adelman (1994), Peterson et al. (2004, 2006) and Aufdenberg et al. (2006) indicates that Vega is pole-on and fast rotator.”
• Interferometric observations of rapidly rotating stars (2005, background): “For example, observations of Vega by Aufdenberg et al. (2006) led the investigators to substantially refine (some might say, revise) the nature and absolute amount of bolometric flux being produced by this star.”
• Gravity darkening in rotating stars (2011, background): “Now, the recent interferometric observations of some nearby rapidly rotating stars by McAlister et al. (2005), Aufdenberg et al. (2006), van Belle et al. (2006), and Zhao et al. (2009) have shown that gravity darkening is not well represented by von Zeipel’s law, which seems to overestimate the…”
• STELLAR DIAMETERS AND TEMPERATURES. III. MAIN-SEQUENCE A, F, G, AND K STARS: ADDITIONAL HIGH-PRECISION MEASUREMENTS AND EMPIRICAL RELATIONS (2013, background): “For instance, Aufdenberg et al. (2006) calculate that the apparent luminosity of the pole on star Vega is 35% larger than its bolometric luminosity, because of our pole-on line of sight.”
• Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer (2017, unknown): “…(2012) 2.041±0.043 Baines et al. (2010) 172167 3.280±0.016 2.930±0.007 Monnier et al. (2012) 3.08±0.03a Mourard et al. (2009) 3.202±0.005a Absil et al. (2006) 3.329±0.006 Aufdenberg et al. (2006) 3.225±0.032 Mozurkewich et al. (2003) 3.28±0.01 Ciardi et al. (2001) 3.24±0.07 Hanbury Brown et…”
• Techniques and Review of Absolute Flux Calibration from the Ultraviolet to the Mid-Infrared (2014, background): “…star, observed poleon, and has a circumstellar disk that contributes to the stellar flux starting around 2 μm and extending to far-infrared wavelengths (Aumann et al. 1984; Su et al. 2005, 2013; Aufdenberg et al. 2006; Sibthorpe et al. 2010; Defrere et al. 2011; Absil et al. 2013; Bohlin 2014).”
• Variations on Debris Disks: Icy Planet Formation at 30-150 AU for 1-3 M☉ Main-Sequence Stars (2008, methodology): “In addition to the observed fluxes at 24, 70, 160, and 850 m (Su et al. 2005), we adopt published values for the age (200 Myr; Su et al. 2006), luminosity (37 L ; Aufdenberg et al. 2006), and mass (2.3 M ; Aufdenberg et al. 2006) of the central star.”