PMH-131 Jan. 2000

PMH-231 Jan. 2000

Nulling Interferometry for Studying Other Planetary Systems: Techniques and

Observations

Phil Hinz

PhD Thesis Defense

Wednesday Jan. 31, 2000

PMH-331 Jan. 2000

Challenges of Finding Planets

Mass of Jupiter is 10-3 Msun

Giant Planet Brightness is: 10-9 Lsun in visible 10-6 Lsun in IR

Dust Disk is 10-4 Lsun in IR

Direct Detection Requirements: large aperture telescopeswavefront correctionsuppression of starlight

Need instrumental development to make scientific progess.

PMH-431 Jan. 2000

Advantages of Direct Detection

•We want to see planets not just infer their existence.

•Direct emission from planets can tell us about their chemical make-up, temperature, etc. . . We can learn more about it.

•Wide orbit planets such as Jupiter or Saturn require prohibitive time baselines for Doppler velocity detection.

PMH-531 Jan. 2000

Bracewell Interferometry

Collector 1 Collector 2

Semi-transparent mirror

left output right output

ΔΦ

Stellar wavefront

Companion wavefront

PMH-631 Jan. 2000

Fizeau Interferometry

Collector 1 Collector 2

PMH-731 Jan. 2000

Resolving Faint Companions

Fizeau interferometry is well –suited forhigh spatial resulotion studies

Pupil-plane interferometry is well-suited forsuppression of starlight.

Star

Companion(1% of star brightness)

Star+Companion

PMH-831 Jan. 2000

Nulling Measurements

dust trdust trdust2

Source Orientation 1 Orientation 22

PSF of single element

Nulling interferometry measures the total flux transmitted by the interference pattern ofthe two elements, convolved with the PSF of a single element.

PMH-931 Jan. 2000

Subtlety 1: Chromaticity of Null

Fraction of light remaining in nulled out put is given by

where

Level of suppression is good over only a narrow bandwidth.

Three fixes: Rotate one beam 180 degrees (Shao and Colavita)Send one beam through focus (Gay and Rabbia)Balance dispersion in air by dispersion in glass (Angel, Burge and Woolf)

Dispersion Compensation allows out-of band light to be used to sense phase (Angel and Woolf 1997)

4

1

4)(

2

))(cos(1)(

0

N

PMH-1031 Jan. 2000

Subtlety 2: True Image Formation

In Bracewell’s concept the beams form images which are mirror versions of one another.

Rotation nulls create images which are rotated versions of one another.

It is only possible to create a true image of the field using dispersion compensation for thesuppression and an interferometer which has an equal number of reflections in each beam.

PMH-1131 Jan. 2000

First Telescope Demonstration of Nulling

Nulling at the MMTNature 1998; 395, 251.

Ambient Temperature Optics

PMH-1231 Jan. 2000

Beam-splitter design

Requirements: Equal reflection and transmission at nulling wavelengthEqual reflection and transmission at phasing wavelengthSymmetric design (to avoid chromatic phase shifts)Substrate suitable for dispersion compensation.

Design:

ZnSe substrate

λ0 /4 air gap

difference in substrate thickness of 39 μm

PMH-1331 Jan. 2000

Phase Compensation of Null

9 9.5 10 10.5 11 11.5 12 12.5 13

0.46

0.48

0.5

0.52

0.54

9 9.5 10 10.5 11 11.5 12 12.5 131 10

6

1 105

1 104

1 103

0.01

Ph

ase

(wav

es)

Inte

nsi

ty

Wavelength (μm)

PMH-1431 Jan. 2000

Beam-splitter Performance

2 4 6 8 10 120

0.5

1

2 4 6 8 10 120

0.5

1

Ref

lect

ion

Inte

nsit

y

Wavelength (μm)

Ph

ase

dif

fere

nce

(wav

es)

phase sensingpassband

Nullingpassband

PMH-1531 Jan. 2000

The Bracewell Infrared Nulling Cryostat

PMH-1631 Jan. 2000

telescope beam

reimaging ellipsoid

beam-splitter

2 μm detector10 micron detector

imaging “channel”

nulling “channel”

Mechanical Design

PMH-1731 Jan. 2000

BLINC’s First Year

PMH-1831 Jan. 2000

Laboratory Setup

HeNe laserDichroic

CO2

laser

Ball mirror “Telescope” mirrorFold mirror

Interferometer

Infrared Camera

PMH-1931 Jan. 2000

Laboratory Results

CO2 laser source yielded a null with an integrated flux of 3x10-4

Entire Airy pattern along with the scattered light disappears in nulled image.

0.5 s exposure images at 10.6 μm

PMH-2031 Jan. 2000

20 15 10 5 0 5 10 15 200

0.25

0.5

0.75

1

path-length (microns)

Inte

nsi

ty

Laboratory Results II

50% bandwidth causes adjacent nulls to be significantly > 0.

Relative depth of theadjacent nulls determinesachromaticity of centralnull.

PMH-2131 Jan. 2000

Constructive image Scanning pathlength

0.5% of peak2% of peak

White=5% of peak

Laboratory Null

PMH-2231 Jan. 2000

Telescope Nulling

PMH-2331 Jan. 2000

•Commissioning run of MIRAC-BLINC, June 10-17, 2000.

•Aligned and phased the interferometer during the first night of observing

•Observed AGB stars, several Herbig Ae stars, and several main-sequence stars.

•Observed again in October, but weather was poor.

Observing at the MMT

PMH-2431 Jan. 2000

Pupil Alignment of BLINC

Right beamouter edge of primary

Left beamouter edge of primary

Left beamsecondary obscuration

Right beamsecondary obscuration

Pupil stop sizefor nullingobservations

PMH-2531 Jan. 2000

Dust outflow around Antares

α Boo

α Sco

constructive destructive

Best nulls of α Boohave a peak ratio of3%. The integrated light is 6% of the constructive image.

The nulled images ofα Sco are 25% of theconstructive images. Suppression of the starlight allows us toform direct images of thedust outflow around thestar

PMH-2631 Jan. 2000

Antares

baseline verticalN

E

baseline horizontal5 arcsec

PMH-2731 Jan. 2000

IRC+10216

Constructive -- Destructive = Point Source

Point source in IRC+10216 is faint compared to its extended dust nebula.

By modulating the point source we can determine its contribution as well as its registration to the nebula. This has been a source of confusion for IRC+10216

PMH-2831 Jan. 2000

IRC+10216

1 arcsec

N

E

11.7 μm

8.8 μm

nulled image constructive - null

PMH-2931 Jan. 2000

Herbig Ae/Be stars

Chiang and Goldreich (1997)have created models to explain the spectral energy distribution of T Tauristars and Herbig Ae/Be stars.

Disk would be only 0.2” across, so too small for direct imaging detection, but would not have a null of < 40\%.

R*

r

τ = 1

τ = αα

PMH-3031 Jan. 2000

Herbig Ae/Be stars

Three nearby Herbig Ae stars observed with BLINC, June 2000.

star d

(pc)

Expected Residual

Flux

Measured Residual

Flux

Position Angle

HD150193 150 41% 0±5% 97 º

HD163296 122 49% -1 ±7%

3 ±3%

94 º

10 º

HD179218 240 41% 3 ±3%

1 ±3%

162 º

87 º

Indicates region of emission is smaller than predicted by model.

PMH-3131 Jan. 2000

Main Sequence Stars

Two nearby main sequence stars observed with BLINC, June 2000: Vega and Altair.

Star Null Residual Flux

Wavelength Position Angle

Vega 14 ±3% 1 ±4% 11.7 μm 133 º

Vega 13 ±3% 0 ±4% 10.3 μm 135 º

Altair 8 ±4% -5 ±5% 10.3 μm 97º

Using the DIRBE model for our solar zodiacal cloud (Kelsall et al. 1998), a limit of approximately 3700 times solar level for Vega and 2500 times solar level for Altair.IRAS photometric limits at 12 μm are approximately 1800 times solar level for both stars.

PMH-3231 Jan. 2000

Nulling Sensitivity

PMH-3331 Jan. 2000

Depth of Null:Star Diameter

0.4 0.3 0.2 0.1 0 0.1 0.2 0.3 0.40

0.2

0.4

0.6

0.8

1

arcseconds

tran

smis

sion

star diameter

PMH-3431 Jan. 2000

MMT Nulling Error Budget

Star diameter

at 10 pc

Star leak

At 11 μm

G2V star

1.6x10-6

Chromatic phase

errors

Beam-splitter

4.0x10-6

Chrom. and Pol. Amp. Errors

Beam-splitter

3.8x10-5

Adaptive Optics

Spatial Error

Temporal Error

Atmosphere

Fitting error

Time lag of system 2.0x10-4 (1.6x10-5)

1.2x10-4 (1.70x10-5)

Error Source Level

Total flux: 3.6x10-4 (7.7x10-5)

PMH-3531 Jan. 2000

Expected Sensitivity

4 6 8 10 12 141 105

1 106

1 107

1 108

1 109

1 1010

Wavelength (μm)

phot

ons/

s/m

2/μ

m/a

rcse

c 2

Sky Background

Telescope Background

L'

M

N

MMT LBT

10-12.2 μm 660 45

M band 190 21

L‘ band 18 2.1

hourJy hourJy

PMH-3631 Jan. 2000

MMT Dust Limits for stars at 10 pc

1 10 100 1 10310

100

1 103

1 104

Cloud density (zodis)

Flu

x in

nu

lled

out

put

of M

MT

(μ

Jy)

dust around an A0 sta

r

F0 star

G0 star

K0 star

M0 star

MMT detection limit

PMH-3731 Jan. 2000

MMT zodiacal dust detection

The short baseline of the MMT gives it 13 times better suppressionof a star than LBT and 450 times better than Keck.

Star Spec. Type Distance

(pc)

Dust Limit

(vs. solar)

Star Leak

Sirius

ε Eri

61 Cyg A

61 Cyg B

α Cmi

τ Ceti

Gl380

ω 2 Eri

70 Oph

Altair

A1V

K2V

K5Ve

K7Ve

F5IV-V

G8Vp

K2Ve

K1Ve

K0Ve

A7IV-V

2.64

3.22

3.48

3.50

3.50

3.65

4.87

5.04

5.09

5.14

0.1

10

29

50

0.9

7

34

29

23

0.6

9.4×10-5

1.0×10-5

7.0×10-6

6.0×10-6

2.3×10-5

9.5×10-6

4.4×10-6

4.3×10-6

4.6×10-6

1.6×10-5

PMH-3831 Jan. 2000

LBT dust limits for stars at 10 pc

1 10 100 1 10310

100

1 103

1 104

Cloud density (zodis)

Flu

x in

nu

lled

out

put

of L

BT

(μ

Jy)

dust around an A0 sta

r

F0 star

G0 star

K0 star

M0 star

LBT detection limit

PMH-3931 Jan. 2000

Planet Limits

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.910

100

1 103

MMT 18

LBT 2.1

age (Gyr)

Flu

x of

5 M

J pl

anet

(μ

Jy)

MMT L' band limit

MMT M band limit

MMT 11 μm limit

L' band flux

N band flux

M band flux of 5 MJ planet

PMH-4031 Jan. 2000

Planet Limits

2 4 6 8 10 12 14 16 18 201

10

100

mass (MJ )

L' b

and

flux

(μ

Jy)

LBT limit

MMT limit

5 Gyr

flux

of 0

.5 G

yr o

ld p

lane

t

1 Gyr

PMH-4131 Jan. 2000

Phase space of Direct Detection

0.1 1 10 1000.1

1

10

100

Separation (AU)

Mas

s (J

upit

er m

asse

s)

MMT limit

LBT limit

Radial velocity limit