Armstrong Chile Dec06 OIsurvey

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A Survey of (Mostly) Current Optical and Infrared Interferometers Tom Armstrong US Naval Research Laboratory Navy Prototype Optical Interferometer (NPOI) tom.armstrong@nrl.navy.mil December 4, 2006

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Michelson’s 20-foot interferometer, Mt. Wilson, California (used mostly in 1921)

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NPOI Keck

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Interferometers currently in operation

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Interferometers currently in operation

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Interferometers under development Recently closed interferometers

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Interferometers under development Recently closed interferometers

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GI2T, Observatoire de la Côte d’Azur Photo: Peter Lawson 2 x 1 m To 50 m baselines 2 μm, visual bands High spectral resolution

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3 x 0.40 m 5 m to 38 m baselines 2 μm band Fiber beam combination IOTA, Mt. Hopkins, Arizona

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5 x 0.40 m 3 m to 100m baselines 500—800 nm band First closure phase image COAST, Cambridge, England

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3 x 1.65 m apertures 5 to 80 m baselines 12 μm band Heterodyne detection ISI, Mt. Wilson, California

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Palomar Testbed Interferometer (PTI), Mt. Palomar, California 3 x 0.18 m apertures 70, 100 m baselines 2 μm band Dual-star feed for small-angle astrometry

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SUSI, Narrabri, Australia Photo: Karina Hall 2 x 0.12 m apertures 5 to 80 m baselines 450—900 μm band Longest baselines

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Navy Prototype Optical Interferometer (NPOI), Anderson Mesa, Arizona 6 x 0.12 m apertures 5 to 80 m baselines 450—850 nm band Astrometry and imaging Largest number of apertures

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3 x 1.8 m apertures 30 to 202 m baselines and 4 x 8.2 m apertures 25 to 85 m baselines 2 μm, 5 μm,10 μm band Multiple backends Largest S. hemisphere apertures Adaptive optics VLTI, Cerro Paranal, Chile

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Keck Interferometer, Mauna Kea, Hawai`i 2 x 10 m apertures 70 m baseline 2 μm, 5 μm, 12 μm band Largest N. hemisphere apertures Also aperture masking

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Mt. Wilson, California: 100-inch & 60-inch telescopes, solar towers—and CHARA 6 x 1 m apertures 35 to 330 m baselines 2 μm band FLUOR fiber beam combiner Longest baseline

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Mauna Kea, Hawai`i 5 apertures, 4 to 10 m To 800 m baselines 2 μm band Fiber combination

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2 x 8 m apertures 14 m baseline center-to-center 22 m baseline edge-to-edge 2 μm band Two telescopes on single mount Large Binocular Telescope, Mt. Graham, Arizona

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4 to 10 x 1.4 m apertures To 500 m baselines 2 μm, visual bands Rapid imaging Magdalena Ridge Observatory, New Mexico

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Sample results: Cepheid pulsations (PTI) Diameter of η Aquilae vs. pulsation phase. Crosses: diameters from PTI Line: diameter inferred from infrared surface brightness method. Combining change in angular diameter (interferometry) with change in physical diameter (radial-velocity data) yields the distance. Lane et al. 1999 Astrophys. J.

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Sample results: Cepheid pulsations (VLTI) Diameter of ℓ Carinae vs. pulsation phase. Circles: diameters from VLTI with VINCI Line: diameter inferred from infrared surface brightness method. Predicted angular diameters from infrared surface brightness methods are in good agreement with measured diameters, giving confidence in the conversion from radial velocities to physical diameter variations. Kervella et al. 2003 Astron. Astrophys.

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RESULTS: Vega is rotating at 93% of breakup velocity. Its equator is distended by 25% and is 2400° K cooler than the pole. We see it nearly pole-on. Vega is the major photometric standard, but model atmospheres do not fit the spectrum. IMAGE: Off-center bright polar cap shows rotation axis is tilted ~5° from the line of sight. Pole-to-equator temperature contrast (2400° K) may explain spectral anomalies. Low secondary maximum shows significant limb darkening. Phase anomalies indicate slight asymmetry. Peterson et al., Nature, 2006 DATA: Sample results: Vega is a rapid rotator (NPOI)

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Sample results: High-precision binary astrometry (PTI) Lane 2005 PTI Position differences between components in right ascension and declination (crosses), with 1-σ error ellipses. Orbital motion is from south to north. -0.230 -0.228 -0.226 -0.224 -0.222 -0.220 -0.218 ΔRA (arcsec) 0.120 0.119 ΔDec (arcsec) HD 171779

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Sample results: High-precision binary astrometry (PTI) Lane 2005 PTI The goal is to detect perturbations in the orbit of a binary component due to an unseen companion (possibly a planet). Typical formal error ellipse is 5 x 100 micro-arcseconds. Fit to linear trend yields an implied repeatability of ~ 15 x 300 micro-arcseconds. Position differences between components in right ascension and declination (crosses), with 1-σ error ellipses. Orbital motion is from south to north. -0.230 -0.228 -0.226 -0.224 -0.222 -0.220 -0.218 ΔRA (arcsec) 0.1199 0.1198 0.1197 0.1196 0.1195 0.1194 0.1193 0.1192 0.1191 ΔDec (arcsec) HD 171779

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Sample results: Polarimetric interferometry with SUSI Visibility vs. baseline length for R Carinae with SUSI at λ900 nm Ireland et al. 2005, Monthly Notices R. A. S., 361, 337 Outflow model Uniform stellar disk (no circumstellar dust) R Carinae is a Mira, a pulsating late-type giant surrounded by dust. Light reflected by the dust is polarized. SUSI data fit a model with a thin shell of dust better than a model with a thicker shell created by steady outflow. Visibility difference between polarizations Visibility for both polarizations 0.08 0.06 0.04 0.02 0.00 -0,02 Δ Visibility 1.0 0.8 0.6 0.4 0.2 0,0 Visibility 0 2 4 6 8 10 12 Baseline (m) 0 2 4 6 8 10 12 Baseline (m) Pulsation phase 0.08 Thin-shell model Note the visibility precision: ± 1.5% to 2%

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Sample results: Rotational distortion of Alderamin (α Cep) with CHARA van Belle et al. 2006, Astrophys. J., 637, 494 Rotational velocity: 280 km/s (83% of breakup velocity) Teff = 8440 K (poles) to 7600 K (equator) Temperature contrast implies that the photosphere is convective. Projected baseline lengths: 250 m to 312 m 2.15 μm wavelength, 0.30 μm bandwidth

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Boden et al. 2005, ApJ, 635, 442 HD 98800 B: Double-lined spectroscopic binary, member of a four-star system. Pre-main-sequence stars. Combine Keck Interferometer data with radial-velocity data and Hubble Fine Guidance Sensor data to find: M = 0.70 Msun and 0.58 Msun. Masses and luminosities do not fit models. Effective temperature Effective temperature Luminosity (Lsun) Luminosity (Lsun) Luminosity (Lsun) Luminosity (Lsun) Solar metallicity Sub-solar metallicity Siess et al. (2000) models Baraffe et al. (1998) models Sample results: Low-mass pre-main-sequence stars with the Keck Interferometer

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Monnier et al. 2000 Astrophys. J. Sample result: Colliding-wind binary WR 98 with Keck aperture masking Image Model