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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-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-1631 Jan. 2000
telescope beam
reimaging ellipsoid
beam-splitter
2 μm detector10 micron detector
imaging “channel”
nulling “channel”
Mechanical Design
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-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-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-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-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
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