science with optical/nir interferometers interferometry week eso santiago, 14-16 january 2002 a....

Science with Optical/NIR Interferometers

Interferometry Week

ESO Santiago, 14-16 January 2002

A. Richichi (ESO Garching)

A. Richichi Interferometry Week, ESO Santiago 16-01-02

Layout of the Tutorial - I

Interferometers

• Types of interferometers under consideration

• Types of interferometry not considered here

• Characteristics of interferometers vs. science drivers

• Illustration of a few representative facilities

Layout of the Tutorial - II

Stars & PMS Stars

• Fundamental Stellar Parameters- diameters, limb darkening, flattening- temperatures- masses- ages

• Binaries

• Stellar Pulsation

• Circumstellar Matter

• Distances

Science with Interferometers

Layout of the Tutorial - III

Exoplanets and BD

• Detection and discrimination

• Basic parameters

• Relationship to other EP/BD detection methods

Extragactic sources

• Detection

• Basic parameters

• Observation strategies

Miscellaneous

• Microlensing

• Solar system objects

Science with Interferometers ctd.

VLTI Science - Main ReferencesESO Symposia: Science with the VLT - 1994 (Walsh/Danziger)

Science with the VLTI - 1996 (Paresce)

From Extrasolar Planets to Cosmology - 1999 (Renzini)

SPIE Interferometry in Optical Astronomy: 1998 Kona, 2001 JENAM,

2000 Munich (22 papers on science with ground-based interferometers)

Workshops: i.e., ESO April 2001, June 2001

Schools: i.e., 1999 Michelson Summer School, 2000 NOVA/ESO/ESA Summer School, 2002 EuroWinter School.

Scientific Objectives of the VLT Interferometer (Paresce, March 2001) (http://www.hq.eso.org/projects/vlti/, abridged in Messenger, 104)

AMBER Scientific Analysis Report, PDR 2000 - MIDI misc.

Science Demonstration Team, PRIMA White Book, ... PR 18/03/01

and 5/11/01

Layout of the Tutorial - IV

Science with the VLT Interferometer• Facility instrumentation (¶ Schöller)

- wavelengths & limiting magnitudes- dates of availability- scientific applications

• Getting ready to observe with the VLTI - guidelines on object selection and proposal preparation- calibrators

• VLTI Data (see Messenger 106, P. Ballester et al.)- format- pipeline- data analysis

• Examples and simulations of VLTI results (given throughout)

Characteristics of Interferometers

• optical to thermal IR ( 0.5m to 20m)- types of detectors- background- atmospheric turbulence (tip-tilt, fringe tracking, AO)- mechanical and optical constraints

• Michelson vs. Fizeau interferometers- homothetic mapping, field of view- types of baselines

• number of telescopes- number of baselines- beam combination (multi-axial, co-axial)- efficiency- closure phases

Other Interferometric Methods

• single-telescope- speckle interferometry- aperture masking

• multi-telescope- intensity interferometer- heterodine detection- nulling interferometry

• space instruments- SIM, Darwin, GAIA

Overview of current Interferometers

facility funding location n. of baseline year ofapertures primary secondary max (m) first fringes

CHARA USA Mt. Wilson 6 1.0 350 1999COAST UK Cambridge 5 0.4 48 1991GI2T F Calern 2 1.5 65IOTA USA, F Mt. Hopkins 2-3 0.45 38 1993ISI USA Mt. Wilson 2-3 1.65 75 1988KECK USA Mauna Kea 2(4) 10 1.8 85(140) 2001LBT USA, D, I Mt. Graham 2 8.4 23 in constr.MIRA-I.2 J Tokyo 2 0.30 6 2001MRO USA New Mexico 3 2.4 100 fundedNPOI USA Arizona 3-6 0.35 64 1994PTI USA Mt. Palomar 3 0.40 110 1995SUSI AUS New South Wales 2 0.14 640VLTI ESO Paranal 4(3) 8.2 1.8 130(205) 2000

apertures (m)

Interferometers on the WEB

facility URL

CHARA http://www.chara.gsu.edu/CHARA/array.htmlCOAST http://www.mrao.cam.ac.uk/telescopes/coast/index.htmlGI2T http://wwwrc.obs-azur.fr/fresnel/gi2t/gi2t.htmIOTA http://cfa-www.harvard.edu/cfa/oir/IOTA/ISI http://isi.ssl.berkeley.edu/KECK http://huey.jpl.nasa.gov/keck/LBT http://medusa.as.arizona.edu/lbtwww/lbt.htmlMIRA-I.2 http://tamago.mtk.nao.ac.jp/mira/MIRA-I_2/mira_1_2.htmlMRO http://www.physics.nmt.edu/research/MRO.htmlNPOI http://ftp.nofs.navy.mil/projects/npoi/PTI http://huey.jpl.nasa.gov/palomar/SUSI http://www.physics.usyd.edu.au/astron/susi/VLTI http://www.hq.eso.org/projects/vlti/

Design vs. Science Drivers

Baseline Length

• Resolution improves with Baseline- “correlated” magnitude decreases- relative errors increase

• Calibrators - accuracy vs baseline- magnitude vs baseline- density- boot-strapping

Wavelength vs. Science Drivers

Wavelength

• Angular Resolution- resolution -1

• Atmospheric Turbulence- phase errors -1 - isoplanatic patch 6/5 - seeing -1/5 - coherence time 6/5

• Source Spectrum - many (but not all!) sources are red- spectral features

Geometry vs. Science Drivers

Telescopes

• Number of telescopes- number of baselines N(N-1)- number of phase closures (N-1)(N-2)/2

• Beam Combiner- complexity drives cost (and size)- efficiency decreases with number of telescopes- new approaches

• Array Geometry- non-redundancy- configuration- NS vs. EW orientation- relocation of telescopes

Closure Phases

from J.D. Monnier, 1999

Examples of Array Geometries - CHARA

Examples of Array Geometries - NPOI

Examples of Array Geometries - VLTI

Stellar effective temperatures

and Fbol are the keys to direct Teff estimates

Teff ()½ (Fbol) ¼ ( /) < 5% typically required

102 stars measured by LO, LBI

Fbol = a 2Teff4

Direct check for theoretical models of stellar atmospheres

• determination of physical characteristics

• understanding of energy production/dissipation mechanisms, stellar evolution, chemical abundances, etc.

• population synthesis models

Teff Direct Measurements - a)

Early and intermediate spectral types, Barnes et al. (1976)

Teff Direct Measurements - b)

Late spectral types, Barnes & Evans (1976)

Teff Direct Measurements - c)

Late spectral types, Barnes & Evans (1976)

Teff Calibration for Cool Giants

Ridgway et al. 1980 Dyck et al. 1996 Perrin et al. 1998 Richichi et al. 1999

Currently 646 measurements of 253 class III stars in CHARM catalogue (Richichi & Percheron 2001)

Teff is still uncertain for types cooler than M7 (several parameters at play). Need monitoring of spectra and photometry.

Teff of Mira stars

From Van Belle et al. 1996

Teff of carbon stars

From Richichi et al. 1995

Teff needs Fbol:

photometric monitoring is strictly required!

Teff calibration for carbon stars

From Van Belle et al. 2000

Multiwavelength monitoring

Teff = 3500 K = 2.0mas

Teff = 2500 K = 3.9mas

Fbol ~ 6%

Teff of cool MS stars

Rationale:

• Direct Teff measurements are very scarce: 7 K and 1M dwarfs (~50 times less than giants)

• Important implications for many fields of astronomy: most common field stars

• Transition to L-BD regime / Outliers

• Mass loss / envelopes / circumstellar environment

• surface features

Name V Sp K phi(mas)16 40 200

HD 128621 1.33 K1V -0.67 7.20 0.851 0.336 0.000V450 Aql ? 6.48 M8V -0.27 4.49 0.940 0.671 0.00541 Ara 5.46 M0V 1.86 2.66 0.978 0.872 0.001BD+20 4139B 8.18 M9 0.88 2.43 0.982 0.892 0.014V1365 Ori 6.84 M6V 1.26 2.37 0.983 0.897 0.019eps Ind 4.69 K4.5V 2.19 2.18 0.986 0.912 0.048HD 45724 6.2 M1 2.25 2.13 0.986 0.916 0.059HD 45588 6.07 M0 2.47 2.01 0.988 0.925 0.089HD 210090 6.35 M1 2.4 1.99 0.988 0.927 0.095BD+29 4582B 8.3 M8 1.55 1.94 0.989 0.930 0.110NSV 1874 6.34 M0V 2.74 1.78 0.990 0.941 0.170GJ 702A 4.2 K0V 2.37 1.76 0.990 0.942 0.175DY Eri 4.41 K1V 2.41 1.74 0.991 0.943 0.184HD 40397 6.8 M2.5 2.53 1.73 0.991 0.944 0.190HD 209709 6.43 M0 2.83 1.70 0.991 0.946 0.201BD+04 4223 8.6 M8 1.85 1.69 0.991 0.946 0.207HD 112278 6.97 M3 2.4 1.68 0.991 0.947 0.211HD 85461 6.52 M0 2.92 1.63 0.992 0.950 0.233CD-48 3065 8.1 M7 1.92 1.63 0.992 0.950 0.237DO 4490 8.7 M8 1.95 1.61 0.992 0.951 0.243

baseline(m)

visibility

Some cool MS stars visible from Paranal

not complete nor accurate!^2

• Select K-M main sequence stars

• Apply Paranal limits

• V<10, K<5

• Use B-V (measured or estimated) to infer angular diameter

• Total ~610 stars

• Best targets 90% < Vis < 20%

1 0.98 0.95 0.9 0.5 0.15 0

Visibility

Statistics of MS cool stars

275030003250350037504000

T eff [K]

• With 1% absolute error on visibility, errors on the angular diameters are between 1% and 5%

• Assume 5% error on bolometric flux

• Errors in Teff would be 1.8% to 3.8%

275030003250350037504000

T eff [K]

• Assume 0.5 mag random error on absolute magnitude

• Simulate random distribution of 200 stars

Simulated Teff calibration

Teff of PMS stars

Rationale:

• Direct Teff measurements do not exist yet

• Permit model-independent location of the stars in the HR diagram

• Check of theoretical tracks

• Implications for age estimates, star and disk formation mechanisms, ...

Practical difficulties:

• they have very small angular diameters!

• a solar precursor ( 5 R ) has 0.30 mas at the distance of Tau-Aur SFR, 0.8 mas at TW Hya

• effect of circumstellar environment

• effect of spots

Surface features in T Tau stars

Doppler imaging of the surface of a T Tau star, V410 Tauri.

Adapted from Surdin & Lamzin (2001).

Desirable to model the effects on visibility.

The age and masses of PMS starsFrom Gomez et al. 1992

Mazzitelli (1989) tracks

3x105 yrs

1x106 yrs

3x106 yrs

1x107 yrs

Relatively high accuracy is required on Teff

Resolving PMS stars with the VLTI

Same diameter, 3 different LD

0.0000

0.2000

0.4000

0.6000

0.8000

1.0000

1.2000

Baseline [m]

Limb-darkening

Important to measure around the first zero of the visibility

Limb-darkening measurements

From Wittkowski et al. (2001)

NPOI, 0.65 to 0.85 m

3 baselines 19 to 38 m

UD =6.82 mas

LD =7.44 mas

FD =7.85 mas

~ 0.1mas

Potential LD measurements with VINCI

Psi Phe, preliminary result: =8.3 ±0.3mas

analysis by M. Wittkowski

ESO/NEVEC IDL DRS

Asymmetries

Fast rotators.

Recent detection of 14% equator/pole flattening in Altair (P=10.4hours, V_eq=210 km/s)

For a solar analogue, flattening is 0.001%

Flattening ratios up to 20% are expected for many B & A fast rotating stars. Details of visibility curves will depend strongly on orientation of the polar axis, and on surface temperature (brightness) differences.

Narrow-band and emission line observations.

Good models are required!

• orbital motions --> masses

• different informations from different types of binary systems

• frequency among YSOs--> key to star formation

• dynamics and evolution of binary/disk systems

• “Special binary stars”: BD companions, hot Jupiters

Two approaches are available to measure orbital motions:

• accurate visibilities (Self-contained, lower precision)

• narrow-angle astrometry (wrt to nearby stars)

Binary stars

Main parameters of binary systems

taken from J. Davis, 1996

Visibilities of binary stars

Simulations of some representative cases of binary systems

Spica: the full picture

taken from J. Davis, 1996

Binaries among YSO

Apparent excess of binary stars in Taurus/Auriga, wrt to the solar stars in the solar neighbourhood.

Possible excess in Oph/Sco.

No excess in Orion.

What can the VLTI do?

Short term

Survey nearby SFRs

• Resolution range

• Include all stars

Benefits

• Calibration

• Fast science results

Spectroscopy

• IR spec. binaries

Survey distant SFRs

• Include fainter stars

Long Term

Nearby SFRs

• Orbits close binaries

• Disks

Distant SFRs

• Potential x103

• Diversity

• SF mechanisms

Extended SEDs

• IR companions

0 20 40 60 80 100 120 140 160 180 200

Baseline [m]

ity 1.00 mas

1.10 mas

Accurate visibilities vs. diffraction limit

0 20 40 60 80 100 120 140 160 180 200

Baseline [m]

ity 1.00 mas

1.01 mas

Orbital motions from accurate visibilities

Binary with two point sources, 1:50 Br. Ratio, J band

Orbital motions by phase referencing

Narrow-angle astrometry can measure the separation from a

distant reference star with 10as accuracy

Orbital motions in a 10AU system (P30 yrs) at 50pc(0.2” separation) could be detected

in one day.

Circumstellar Structure

Close circumstellar shells

Mass loss

Close companions, tidal interactions

IRC +10216

Note: no long-baseline interferometric observations yet!

Atmospheres of AGB stars

(Karovska et al. 1997)

HST observation of Mira

Circumstellar emission

From Mennesson et al. (2000).

Asymmetric envelope with the VLTI

Diameter vs. Hour Angle

0.820.840.860.880.900.920.940.960.981.001.02

0:00 1:12 2:24 3:36 4:48 6:00 7:12 8:24

UT Time

-3.00 -2.00 -1.00 0.00 1.00 2.00 3.00

Hour Angle

) 23-Oct

24-Oct

10-Nov

16-Nov

18-Nov

VLTI commissioning observations of Mira

Detection of the envelope around Mira

-20.0 -15.0 -10.0 -5.0 0.0

23-Oct

24-Oct

10-Nov

16-Nov

18-Nov

The environment around YSO

500 AU Model for IRAS 16293:1629, adapted from Surdin & Lamzin (2001)

Herbig AeBe stars

HAEBEs are young intermediate mass PMS stars

Ages in the 105 and 107 yrs range, distances 100-300pc

Masses in the 2-8 M range

Analogue to T Tauris

Likely progenitors of Vega-like debris disk stars

Very large IR excess due to CS material in a disk, possible site of planetary formation

some have mm interferometry sizes of several 100AU (~sec”)

~1AU in K, 10-20AU in N slides from R. van Boekel, F. Paresce

Disks around Herbig AeBe starsSED can be reproduced by

a passive irradiated flaring disk model (Dullemond et al., 2001) determined mainly by:

m, L, Te and d of star (known)

total mass and opacity of dust

Rin, Rout inner and outer disk radius

Hrim, height of inner wall

inclination of disk to LOS

VLTI Objective is to test the spatial predictions of the model and to strongly constrain free parameter space

Model visibilities and parameters

Other parameters

Consistency with SED

Observations of T Tau

Akeson et al. 2001

Refining dust models by interferometry

Akeson et al. 2001

Measuring distances by interferometry

Parallax

Astrometry is possible with some interferometers. Precisions of 10-100 arcsec are possible.

Cepheids

Traditionally the standard candles in the distance scale. The angular diameter of the nearest ones is now potentially within reach of interferometers.

Eclipsing Spectroscopic Binaries

An alternative standard candle.

Rationale:

• Period-Luminosity Law

• Standard Candle

• Non-Radial modes?

• Details of pulsation lightcurves not yet completely understood

What modern interferometry can achieve:

• Measurement of angular diameters, with spectacular improvement over current data

• A priori information available, high efficiency

• Repeated measurements necessary

Cepheid Stars

Some Cepheids visibile from Paranal

Data provided by P. Kervella

Simulated Observations of Zeta Geminorum withVINCI/VLTI Siderostats

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Angular size (milliarcsec)

Single measurement: +/- 4 asAbsolute calibration: +/- 9 as

IOTA/Fluor

Kervella et al. (2000)

Zeta Gem

Simulation by P. Kervella

Rationale:

• Eclipses give orbital elements in absolute units

• By-product: stellar radii (calibration, still uncertain, could yield distance)

• Astrometric orbit: yield distance with higher accuracy

• Use as a standard candle

Furthermore:

• Case of binaries with partially resolved discs

• Characteristics (br. ratio, period, epoch) can be estimated in advance, high efficiency

• Repeated measurements desirable

Eclisping spectroscopic binaries

Orbits of well-detached eclipsing binaries

Orbits of contact eclipsing binaries

Eclipsing binaries as M-m indicators

Distance to the LMC from the eclipsing binary HV 2274 (Guinan et al. 1998, Udalski et al. 1998).

Uncertainty due to reddening introduces a significant difference in the [M-m]

(18.47 vs. 18.22)

d V K Spectrum a[mas]estim.

Zet Phe 1.0823082 -55.144474 3.97 4.3 B6V+... 0.598

Del Lib 15.0058349 -8.310820 4.95 5.0 B9.5V 0.684

TZ For 3.1440093 -35.332759 6.89 5.3 G2V 3.254

TY Pyx 8.5942722 -27.485869 6.90 5.3 G5V 1.021

SZ Psc 23.1323786 2.403158 7.44 5.6 K1IV-V+... 0.792

V624 Her 17.4417247 14.243624 6.20 5.8 A3m 0.540

HU Tau 4.3815830 20.410500 5.86 5.9 B8V 0.506

Z Her 17.5806980 15.082190 7.27 5.9 F4IV-V 0.716

CD Tau 5.1731153 20.075463 6.77 5.9 F7V 0.848

ZZ Boo 13.5609518 25.550736 6.78 5.9 F2V 0.765

GG Lup 15.1856375 -40.471760 5.59 5.9 B7V 0.351

U Oph 17.1631716 1.123796 5.90 5.9 B5Vnn+... 0.315

Quick referecence dataCoordinatesCross–Identifications

Some eclipsing binaries from Paranal

Data provided by B. Paczynski

The hunt for extrasolar planets

Mass function of extrasolar planets in units of Jupiter mass detected so far out of ~1000stars from Queloz (ESA SP-451, 2000)

Need direct detection, to derive separation and resolve the orbital parameters.

Interferometry is the most promising technique from the ground.

Extrasolar planets as special binary stars

Astrometry with PRIMA

Phased implementation plan

Accuracy: 50 arcsec initially, later 10 arcsec

Reference star within 30”

Limiting magnitudes eventually K>18 UTs, 15 ATs.

equip ATs first, later UTs

Detection without PRIMA

From Lopez & Petrov (1999)

Extragalactic Science

• Quasars, AGNs, Seyferts

• SNe in distant galaxies

Requirements

Can we find a reference star nearby? PRIMA!• Limit set by AT/UT, wavelength, visibility, field separation

• Statistical approach

What can we expect to measure?• Issue of field of view, imaging vs. parametric models

• Does [magnitude x visibility] kill us?

• Quasars, AGNs, Seyferts

• SNe in distant galaxies

Requirements

Can we find a reference star nearby? PRIMA!• Limit set by AT/UT, wavelength, visibility, field separation

• Statistical approach

What can we expect to measure?• Issue of field of view, imaging vs. parametric models

• Does [magnitude x visibility] kill us?

Kmag=9.3 witin 0.2”. [J-H]=7.0 [H-K]=3.8

NGC 1068 observed with AO (K, H) [Rouan et al. 1998]

NGC 1068

NGC 1068 by speckle Wittkowski et al. (1998)

K band, 6m (0.076mas)

Note: when the visibility goes down, the SNR goes down.

The visibility of NGC 1068

The issue of image complexity4 telescopes, 6 hoursModel 8 telescopes, 6 hours

Simulation made by

C. Haniff (COAST)

Position of photocenter wrt nearby bright star

New position of photocenter

Phase Shift

SN and transient phenomena

Microlensing

Delplancke, Gorski, Richichi (2001)

Photocenter wobble

Min_d=300 mas

MF606W=26.5

Using D=61pc

M=1.4M

Predicted shift=0.6mas

Duration ~1 year

Aim: direct mass determination of an isolated neutron star, with high accuracy and

independently of model assumptions.

The neutron star RX J185635-3754

Aim: direct determination of the diameter of TNO. The largest one, recently observed with AVO, has a size of 1200km @ 1.5DN, or ~40mas.

VLTI case: one can measure ~10x smaller TNOs with the VLTI. The luminosity will decrease correspondingly. KX76 has K~18, so we need to go fainter than that.

At the same time, UT measurements of objects as large as KX76 will sample the visibility beyond the first minimum, permitting studies on 2nd order geometrical properties.

The size of Trans-Neptunian Objects

MIDI overviewInstrument Overview - MIDI

[D/F/NL; PI: Heidelberg]

Paranal: November 2002

First Fringes with UTs: December 2002

Mid IR instrument (10–20 m) , 2-beam, Spectral Resolution: 30-260

Limiting Magnitude N ~ 4 (1.0Jy, UT with tip/tilt, no fringe-tracker) (0.8

N ~ 9 (10mJ, with fringe-tracker) (5.8 AT)

Visibility Accuracy 1%-5%

Airy Disk 0.26” (UT), 1.14” (AT)

Diffraction Limit [200m] 0.01”

[F/D/I; PI: Nice]

Paranal: January 2003

First Fringes with UTs (AO): July 2003

Near IR Instrument (1–2.5 m) , 3-beam combination (closure phase)

Spectral dispersion: ~35, ~1000, ~10000

Limiting Magnitude K =11 (specification, 5, 100ms self-tracking)

J=19.5, H=20.2, K=20 (goal, FT, AO, PRIMA, 4

hours)

Visibility Accuracy 1% (specification), 0.01% (goal)

Airy Disk 0.03”/0.06” (UT), 0.14”/0.25” (AT) [J/K band respectively]

Diffraction Limit [200m] 0.001” J, 0.002” K

AMBER overview

MIDI Goals for GTO, first runs

AMBER Scientific Drivers

Idiosyncrasies of interferometry

☼ two telescopes do not point as one

☼ night shadows on Paranal

☼ left is right, up is down, 30 = 435 = 254 = 10!

☼ get your dark hours right

☼ magnitudes are not your usual magnitudes

☼ integration time and Earth rotation

☼ living in Fourier space

☼ always shoot in the right spot

☼ calibrate, calibrate, calibrate!

Calibrators!

VLTI October 24-25, 2001

UT TIME

Aver. 67.3% 2.3%

Cal 1 w.m 67.7% 0.2%Cal 2 w.m. 68.6% 0.2%Cal 3 65.2% 0.4%Cal 4 w.m. 62.8% 1.0%

Vm,1= Vo,1

Vm,2= Vo,2

=transfer f.

Fringes on the WEB

ESO VLTI:

http://www.hq.eso.org/projects/vlti/

AMBER and MIDI:

http://buz.obs-nice.fr/amber/

http://www.mpia-hd.mpg.de/MIDI/

This presentation:

http://www.eso.org/~arichich/download/iwtutorial/

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