1 survey of the world’s optical / ir interferometers fourth advanced chilean school of...

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Survey of the World’s Optical / IR InterferometersFourth Advanced Chilean School of Astrophysics

A Survey of (Mostly) Current

Optical and Infrared Interferometers

Tom ArmstrongUS Naval Research Laboratory

Navy Prototype Optical Interferometer(NPOI)

[email protected] 4, 2006

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

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CHARA

NPOI

Keck

SUSI

PTI

VLTI

Keck

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Location Apertures Baselines Wavelengths

VLTIwww.eso.org

Cerro Paranal, Chile3 x 1.8 m

4 x 8.2 m

30 to 202 m

25 to 85 m

10 μm, 5 μm,

2 μm bands

CHARA www.chara.gsu.edu

Mt. Wilson, California, USA 6 x 1 m 35 to 300 m 2 μm band

NPOIwww.npoi.lowell.edu

Anderson Mesa, Arizona, USA 6 x 12 cm 5 to 80 m 450 – 850 nm

PTIwww.pti.jpl.nasa.gov

Mt. Palomar, California, USA 3 x 12 cm 70 m, 100 m 2 μm band

Keck Interferometerwww.keck.cara.edu

Mauna Kea, Hawai`i, USA 2 x 10 m 70 m10 μm, 5 μm,

2 μm bands

SUSI www.physics.usyd.au

Narrabri, New South Wales, Australia

2 x 12 cm 5 to 600 m 450 – 900 nm

ISIwww.isi.berkeley.edu

Mt. Wilson, California, USA 3 x 1.65 m 5 to 80 m 10 μm band

MIRA-I (under

development) Tokyo, Japan 2 x 25 cm To 30 m Visual band

Interferometers currently in operation

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Notes

VLTIwww.eso.org

Multiple backends. Largest telescope apertures in Southern Hemisphere. Adaptive optics.

CHARA www.chara.gsu.edu

FLUOR fiber beam combiner.

NPOIwww.npoi.lowell.edu

Two arrays: Wide-angle astrometry; Imaging. 35 cm and 1.4 m apertures in near future (3 years?)

PTIwww.pti.jpl.nasa.gov

Dual-star feed.

Keck Interferometerwww.keck.cara.edu

Largest telescope apertures in Northern Hemisphere. Aperture masking also available.

Outrigger array (1.8 m telescopes) cancelled.

SUSI www.physics.usyd.au

Longest baselines.

ISIwww.isi.berkeley.edu

Heterodyne detection.

Interferometers currently in operation

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MROI (under design) www.mro.nmt.edu

Magdalena Ridge, New Mexico, USA

4 to 10 x 1.5 m To 500 m 2 μm, visual bands

LBT (under development)

www.lbt.uarizona.edu

Mt. Graham, Arizona, USA

2 x 8 m14 m center-to-center

22 m edge-to-edge2 μm band

`OHANA (under development)

www.ohana.eso.org

Mauna Kea, Hawai`i, USA

5: 4 m to 10 m To 800 m 2 μm band

Interferometers under development


IOTA (closed July ’06) www.iota.cfa.org

Mt. Hopkins, Arizona, USA

3 x 40 cm 5 to 38 m 2 μm band

COAST (MROI testbed after ’06) www.coast.uc.uk

Cambridge, UK 5 x 40 cm 3 to 100 m 500 – 800 nm

GI2T (closed June ’06)

www.gi2t.unice.fr

Obs. Côte d’Azur, France

2 x 1 m To 50 m 2 μm, visual bands

Recently closed interferometers

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Notes

MROI (under design) www.mro.nmt.edu

Goal is ~ 100 AGNs.

LBT (under development)

www.lbt.uarizona.eduTwo telescopes on a single mount (no need for delay lines).

`OHANA (under development)

www.ohana.eso.orgFibers link existing telescopes. First fringes attained in ’06.

Interferometers under development

Notes

IOTA (closed July ’06) www.iota.cfa.org

First use of fiber beam combiner.

COAST (MROI testbed after ’06) www.coast.uc.uk

First image using closure phase.

GI2T (closed June ’06)

www.gi2t.unice.frHigh spectral resolution backend.

Recently closed interferometers

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GI2T, Observatoire de la Côte d’Azur Photo: Peter Lawson

2 x 1 mTo 50 m baselines2 μm, visual bandsHigh spectral resolution

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3 x 0.40 m5 m to 38 m baselines2 μm bandFiber beam combination

IOTA, Mt. Hopkins, Arizona

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5 x 0.40 m3 m to 100m baselines500—800 nm bandFirst closure phase image

COAST, Cambridge, England

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3 x 1.65 m apertures5 to 80 m baselines12 μm bandHeterodyne detection

ISI, Mt. Wilson, California

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Palomar Testbed Interferometer (PTI), Mt. Palomar, California

3 x 0.18 m apertures70, 100 m baselines2 μm bandDual-star feed forsmall-angle astrometry

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SUSI, Narrabri, Australia Photo: Karina Hall

2 x 0.12 m apertures5 to 80 m baselines450—900 μm bandLongest baselines

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Navy Prototype Optical Interferometer (NPOI), Anderson Mesa, Arizona

6 x 0.12 m apertures5 to 80 m baselines450—850 nm bandAstrometry and imagingLargest number of apertures

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3 x 1.8 m apertures30 to 202 m baselinesand4 x 8.2 m apertures25 to 85 m baselines2 μm, 5 μm,10 μm bandMultiple backendsLargest S. hemisphere aperturesAdaptive optics VLTI, Cerro Paranal, Chile

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Keck Interferometer, Mauna Kea, Hawai`i

2 x 10 m apertures70 m baseline2 μm, 5 μm, 12 μm bandLargest N. hemisphere aperturesAlso aperture masking

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Mt. Wilson, California: 100-inch & 60-inch telescopes, solar towers—and CHARA

6 x 1 m apertures35 to 330 m baselines2 μm bandFLUOR fiber beam combinerLongest baseline

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Mauna Kea, Hawai`i5 apertures, 4 to 10 mTo 800 m baselines2 μm bandFiber combination

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2 x 8 m apertures14 m baseline center-to-center22 m baseline edge-to-edge2 μm bandTwo telescopes on single mount

Large Binocular Telescope, Mt. Graham, Arizona

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4 to 10 x 1.4 m aperturesTo 500 m baselines2 μm, visual bandsRapid 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 PTILine: 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 VINCILine: 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.

2

0

2

22 0RA offset (mas)

Dec

off

set

(mas

)

Wavelength (m)0.6 0.8

|V1 V

2 V

3|

0.08

0.04

0.00

Phase anomalies indicate slight asymmetry.

Wavelength (m)

Clo

sure

ph

ase

(deg

)

0

180

0.6 0.8

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

ΔD

ec (

arc

se

c) 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

ΔD

ec (

arc

se

c)

HD 171779

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Sample results: Polarimetric interferometry with SUSI

Visibility vs. baseline length for R Carinae with SUSI at λ900 nmIreland 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 V

isib

ilit

y

1.0

0.8

0.6

0.4

0.2

0,0

Vis

ibil

ity

0 2 4 6 8 10 12Baseline (m)

0 2 4 6 8 10 12Baseline (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 m2.15 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 temperatureEffective temperature

Lu

min

osi

ty (

Lsu

n)

Lu

min

osi

ty (

Lsu

n)

Lu

min

osi

ty (

Lsu

n)

Lu

min

osi

ty (

Lsu

n)

Solar metallicity Sub-solar metallicity

Sie

ss

et

al.

(2

00

0)

mo

de

lsB

ara

ffe

et

al.

(1

99

8)

mo

de

ls

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 98with Keck aperture masking

Image

Model

1 survey of the world’s optical / ir interferometers fourth advanced chilean school of...

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