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31 Jan. 2000 PMH-1 Nulling Interferometry for Studying Other Planetary Systems: Techniques and Observations Phil Hinz PhD Thesis Defense Wednesday Jan. 31, 2000 31 Jan. 2000 PMH-2 Challenges of Finding Planets Mass of Jupiter is 10-3 Msun Giant Planet Brightness is: Dust Disk is 10-4 Lsun in IR 10-9 Lsun in visible 10-6 Lsun in IR Direct Detection Requirements: large aperture telescopes wavefront correction suppression of starlight Need instrumental development to make scientific progess. 31 Jan. 2000 PMH-3 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. 31 Jan. 2000 PMH-4 Bracewell Interferometry ΔΦ Stellar wavefront Semi-transparent mirror Collector 1 31 Jan. 2000 left output right output Collector 2 PMH-5 Fizeau Interferometry Collector 1 31 Jan. 2000 Collector 2 PMH-6 Resolving Faint Companions Fizeau interferometry is well –suited for high spatial resulotion studies Pupil-plane interferometry is well-suited for suppression of starlight. Star Star+Companion Companion (1% of star brightness) 31 Jan. 2000 PMH-7 Nulling Measurements Nulling interferometry measures the total flux transmitted by the interference pattern of the two elements, convolved with the PSF of a single element. Source dust Orientation 1 trdust Orientation 22 trdust2 PSF of single element 31 Jan. 2000 PMH-8 Subtlety 1: Chromaticity of Null Fraction of light remaining in nulled out put is given by where N ( ) 1 cos( ( )) 2 ( ) 0 1 4 4 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) 31 Jan. 2000 PMH-9 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 the suppression and an interferometer which has an equal number of reflections in each beam. 31 Jan. 2000 PMH-10 First Telescope Demonstration of Nulling Nulling at the MMT Nature 1998; 395, 251. Ambient Temperature Optics 31 Jan. 2000 PMH-11 Beam-splitter design Requirements: Equal reflection and transmission at nulling wavelength Equal reflection and transmission at phasing wavelength Symmetric design (to avoid chromatic phase shifts) Substrate suitable for dispersion compensation. Design: difference in substrate thickness of 39 μm ZnSe substrate λ0 /4 air gap 31 Jan. 2000 PMH-12 Phase Compensation of Null Phase (waves) 0.54 0.52 0.5 0.48 0.46 9 9.5 10 Intensity 31 Jan. 2000 3 1 10 4 1 10 5 1 10 6 11 11.5 12 12.5 13 11.5 12 12.5 13 Wavelength (μm) 0.01 1 10 10.5 9 9.5 10 10.5 11 PMH-13 Reflection Intensity Beam-splitter Performance 1 0.5 Phase difference (waves) 0 1 4 2 4 6 8 Wavelength (μm) 10 12 Nulling passband 0.5 0 31 Jan. 2000 2 phase sensing passband 6 8 10 12 PMH-14 The Bracewell Infrared Nulling Cryostat 31 Jan. 2000 PMH-15 Mechanical Design telescope beam 10 micron detector 2 μm detector imaging “channel” nulling “channel” reimaging ellipsoid 31 Jan. 2000 beam-splitter PMH-16 BLINC’s First Year 31 Jan. 2000 PMH-17 Laboratory Setup Infrared Camera Fold mirror Ball mirror “Telescope” mirror CO2 laser Interferometer 31 Jan. 2000 HeNe laser Dichroic PMH-18 Laboratory Results 0.5 s exposure images at 10.6 μm 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. 31 Jan. 2000 PMH-19 Laboratory Results II 1 50% bandwidth causes adjacent nulls to be significantly > 0. Intensity 0.75 Relative depth of the adjacent nulls determines achromaticity of central null. 0.5 0.25 0 20 15 10 5 0 5 10 15 20 path-length (microns) 31 Jan. 2000 PMH-20 Laboratory Null Constructive image 2% of peak Scanning pathlength White=5% of peak 0.5% of peak 31 Jan. 2000 PMH-21 Telescope Nulling 31 Jan. 2000 PMH-22 Observing at the MMT •Commissioning run of MIRACBLINC, 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. 31 Jan. 2000 PMH-23 Pupil Alignment of BLINC Right beam outer edge of primary Left beam outer edge of primary 31 Jan. 2000 Left beam secondary obscuration Pupil stop size for nulling observations Right beam secondary obscuration PMH-24 Dust outflow around Antares constructive α Boo α Sco 31 Jan. 2000 destructive Best nulls of α Boo have a peak ratio of 3%. The integrated light is 6% of the constructive image. The nulled images of α Sco are 25% of the constructive images. Suppression of the starlight allows us to form direct images of the dust outflow around the star PMH-25 Antares 5 arcsec baseline horizontal 31 Jan. 2000 baseline vertical PMH-26 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 31 Jan. 2000 PMH-27 IRC+10216 11.7 μm 1 arcsec 8.8 μm nulled image 31 Jan. 2000 constructive - null PMH-28 Herbig Ae/Be stars τ=α α R* τ=1 r Chiang and Goldreich (1997) have created models to explain the spectral energy distribution of T Tauri stars 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\%. 31 Jan. 2000 PMH-29 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. 31 Jan. 2000 PMH-30 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. 31 Jan. 2000 PMH-31 Nulling Sensitivity 31 Jan. 2000 PMH-32 Depth of Null:Star Diameter 1 transmission 0.8 0.6 0.4 0.2 0 0.4 0.3 0.2 0.1 0 0.1 0.2 0.3 0.4 arcseconds star diameter 31 Jan. 2000 PMH-33 MMT Nulling Error Budget Error Source Star diameter at 10 pc Star leak At 11 μm Chromatic phase errors Beam-splitter Chrom. and Pol. Amp. Errors Beam-splitter Adaptive Optics Spatial Error Temporal Error Atmosphere Fitting error Time lag of system G2V star 1.6x10-6 4.0x10-6 3.8x10-5 Total flux: 31 Jan. 2000 Level 2.0x10-4 1.2x10-4 (1.6x10-5) (1.70x10-5) 3.6x10-4 (7.7x10-5) PMH-34 Expected Sensitivity 1 10 10 photons/s/m 2/μm/arcsec 2 1 10 N 9 M 1 10 8 1 10 7 1 10 6 1 10 MMT Jy hour L' LBT Jy hour 10-12.2 μm 660 45 M band 190 21 L‘ band 18 2.1 5 4 6 8 10 12 14 Wavelength (μm) 31 Jan. 2000 PMH-35 Flux in nulled output of MMT (μJy) MMT Dust Limits for stars at 10 pc 1 10 4 1 10 3 MMT detection limit 100 10 1 10 100 1 10 3 Cloud density (zodis) 31 Jan. 2000 PMH-36 MMT zodiacal dust detection The short baseline of the MMT gives it 13 times better suppression of a star than LBT and 450 times better than Keck. 31 Jan. 2000 Star Spec. Type Distance (pc) Dust Limit Star Leak (vs. solar) 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 0.1 10 29 50 0.9 7 34 29 23 0.6 2.64 3.22 3.48 3.50 3.50 3.65 4.87 5.04 5.09 5.14 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-37 LBT dust limits for stars at 10 pc 4 3 Flux in nulled output of LBT (μJy) 1 10 1 10 100 LBT detection limit 10 1 10 100 1 10 3 Cloud density (zodis) 31 Jan. 2000 PMH-38 Planet Limits Flux of 5 MJ planet (μJy) 1 10 3 MMT 11 μm limit MMT M band limit 100 MMT L' band limit 10 0.1 31 Jan. 2000 0.2 0.3 0.4 0.5 age (Gyr) 0.6 0.7 0.8 0.9 PMH-39 Planet Limits L' band flux (μJy) 100 MMT limit 10 LBT limit 1 31 Jan. 2000 2 4 6 8 10 mass (MJ ) 12 14 16 18 20 PMH-40 Phase space of Direct Detection Mass (Jupiter masses) 100 10 LBT limit 1 0.1 0.1 31 Jan. 2000 MMT limit 1 Separation (AU) 10 100 PMH-41