Dust Busters: When Worldletts Collide

Dust Busters: When Worldletts Collide
Glenn Schneider Steward Observatory, University of Arizona (NICMOS/IDT) … and, what’s happening @ ~ 100 AU?

HST Provides a Unique Venue for High Contrast Imaging
• Diffraction Limited Imaging in Optical/Near-IR •> 98% Strehl all ls Background Rejection 1.6mm: ~10-6 1” 1.1mm: ~10-5 in 2”-3” annulus • Highly STABLE PSF • Coronagraphy: NICMOS STIS, ACS • Intra-Orbit Field Rotation NIR High Dynamic Range Sampling NICMOS/MA: Dmag=19.4 (6 x 4m)

H-Band (F160W) Point-Source Detectability Limits
Two-Roll Coronagraphic PSF Subtraction 22m Total Integration DH(5s) = r” r” 2 . . Photon Noise Dominated Read Noise Dominated H=6.9

Scientific Areas of Investigation
via PSF-Subtracted Coronagraphic Imaging Circumstellar Disks Extra-Solar Planet & Brown Dwarf Companions

HST/NICMOS Coronagphic Imaging Surveys Carried Out
by the IDT’s Environments of Nearby Stars (EONS) Team DISK Candidates: 22 young (< 100 Myr) unembedded (largely unobscured by primordial material) K-A stars within ~ 100 pc with with known far-IR exceses. BROWN DWARF/ VLM Star Candidates: 32 HighProper Motion Late M-Dwarf Stars within ~ 10 pc. PLANET/BROWN DWARF Candidates: 38 young ‘High’ Proper Motion within ~ 50 pc with, including all (but one) of the then-know Members of the TW Hya Assn.

The Dusty Disk/Planet Connection
Current theories of disk/planet evolution suggest a presumed epoch of planet-building via the formation and agglomerative growth of embryonic bodies, and the subsequent accretion of gaseous atmospheres onto hot giant planets, is attendant with a significant decline in the gas-to-dust ratios in the remnant protostellar environments. In this critical phase of newly formed (or forming) extra-solar planetary systems, posited from a few megayears to a few tens of megayears, the circumstellar environments become dominated by a second-generation population of dust containing larger grains arising from the collisional erosion of planetesimals.

Planet-Building Timeline
C o l a p s i n g r t f m - e y d k 1 6 T u , O h c HH 30

C o l a p s i n g r t f m - e y d k 1 6 T u , O h c R o c k y r e s f g i a n t p l m

C o l a p s i n g r t f m - e y d k 1 6 T u , O h c a c r e t g s o u m p h T W H y d 1 7 A G i n l 141569A

C o l a p s i n g r t f m - e y d k 1 6 T u , O h c m) 4 R W H 7 A G Planet-Building Timeline T e r s t i a l p n f o m C g y , K u c b ? 1 8 9 E h v S : 5 x . P H d A Primary Dust (≤ m) Secondary Dust (≥ Locked to Gas Collisional erosion Clearing Timescales: P-R drag few 10 Rad. Pressure: ~ 10 F R W

Cooling Curves for Substellar Objects
. . Cooling Curves for Substellar Objects Evolution of M Dwarf Stars, Brown Dwarfs and Giant Planets (from Adam Burrows) HR 7329B GL577B/C GL 503.2B CD -33° 7795B -2 200M jup 80M jup -4 TWA6B ? L/Lsum 10 Log sun -6 14M jup -8 STARS (Hydrogen burning) BROWN DWARFS (Deuterium burning) JUPITER PLANETS SATURN -10 6 7 8 9 10 Log Age (years) 10

DIRECT DETECTION OF YOUNG PLANETS A PRIME CANDIDATE (TWA 6 ‘B’)
MECHANICS & A PRIME CANDIDATE (TWA 6 ‘B’)

CORONAGRAPHIC COMPANION DETECTION Multiaccum Imaging at two S/C orientations In a single visability period. Background objects rotate about occulted Target. PSF structures and optical artifacts do not. TWA6. Two Integrations: Median of 3 Multiaccum Each D Roll = 30° D Time = 20 minutes

background brightness is reduced by an ADDITIONAL factor
Above: Coronagraphic Images D Roll: 30° Above: Coronagraphic Images D Roll: 30° Left: Difference Image Same display dynamic range At r=2.5” (where image of companion emerges), background brightness is reduced by an ADDITIONAL factor of 50 over raw coronagraphic gain (of appx 4). Each image of TWA6B is S/N ~20 in difference frame. H companion = 20.1 DH = 13.2

Minimize local residuals in region near companion image while constraining background to be statistically zero...

Positive Image Extracion

Negative Image Extraction (Inverted)

Rotate Negative Extraction About Occulted Target And Add After Inversion

Is it a Point Source? Model and Remove Diffraction Spike Residuals*
*DSPK Is it a Point Source?

Radial Profile, Photocentric Moment & Gaussian Fitting
Is it a Point Source?

How Deep? Sensitivity Completeness... Residuals from 2D Gaussian Model
Subtracted from Data Are Identical to Those Expected from NICMOS Camera 2 F160W PSF at the Coronagraphic Focus. How Deep? Sensitivity Completeness...

Sensitivity: Noise Equavalent Background Assessment

Detectability and Spatial Completeness
(r,q) Dependence via Model PSF Implantation Observed Model* Nulled Implant *TinyTim 5.0 HST+NICMOS Optical Model - Krist

Detectability: (r,q) Dependence via Model PSF Implantation

Photometric Efficacy & Statistical Significance
. 2 5 2 1 6 S/N (Positive Implant Only) % Recovered Flux 1 2 8 4

TWA6B Detection Illustrates Performance Repeatability
Two-Roll Coronagraphic PSF Subtraction 22m Total Integration DH(5s) = r” r” 2 . .

TW Hya Assn K7primary, D = 55pc Age = 10 Myr r=2.54”, 140AU DH =13.2 (LB/A)[H]=5 x10-6 Habs = 16.6 Implies: • Mass ~ 2Jupiter • Teff ~ 800K IF Companion... TWA 6A/B S/NTWA6B = 35

A Jovian Planet @ > 140 AU?
• RV Surveys suggest ~ 5% MS *s have 0.8—8 Mjup companions @ d < 3AU from their primaries. • NOT Where Giant Planets are found in our own Solar System WHY ARE THEY THERE? Posited*: Mutual interactions within a disk can perturb one young planet to move into a < 1AU eccentric orbit (as inferred from RV surveys), and the other… Ejected (but bound) to very large separations, > 100AU * e,g., Lin & Ida (ApJ, 1997); Boss (2001, IAU Symp 202)

Is it, or Isn’t It? • Undetected in NICMOS 0.9mm Followup Observation I-H > 3 • Marginally Detected in 6-Orbit Binned STIS G750L Spectrum • Colors Consistent with 2 Mjup, 10 Myr, “Hot” Giant Planet Instrument Band Bandpass Mag NICMOS/C2 F160W — NICMOS/C2 F090M —1.00 >23.1 STIS/G750L I extract 0.81—0.99 ~25.4 STIS/G750L R extract 0.63—0.77 >27.2 If NOT a hot young planet, it must be a Highly exotic object!

Is it, or Isn’t It? • Undetected in NICMOS 0.9mm Followup Observation I-H > 3 • Marginally Detected in 6-Orbit Binned STIS G750L Spectrum • Colors Consistent with 2 Mjup, 10 Myr, “Hot” Giant Planet* 20.1 >23.1 ~25.4 >27.2 Spectrum from A. Burrows * Sudarsky et al., 2000 • Keck/AO Astrometric (PM) Follow-up Thus-Far Inconclusive

Is it, or Isn’t It? A differential proper motion measure will be obtained with NICMOS. If common proper motions are confirmed we will request time for NICMOS grism spectrophotometry to obtain a near-IR spectrum. 20.1 >23.1 ~25.4 >27.2

Is it, or Isn’t It? Time will tell… But, if not TWA6 ‘B’, the technical capability to image such young planets is no longer in the future.

Direct (Scattered Light) Imaging of Dusty Debris
Observing scattered light from circumstellar debris has been observationally challenging because of the very high Star:Disk contrast ratios in such systems. B.A. Smith & R.J. Terrile 6" radius coronagraphic mask, Las Campanas (discovery image) Until very recently the large, and nearly edge-on disk around b Pictoris remained the only such disk imaged. b Pictoris Resolved imaging spatial distribution of dust/debris. Asymmetries (radial & azimuthal): • May implicate low-mass perturbers (planets) from: Rings, Central Holes, Gaps, Clumps, Arcs, Arclets • Help Elucidate the scattering & physical properties of the grains.

Dusty Disks with Radial and Hemispheric Brightness Anisotropies and Complex Morphologies, Possibly Indicative of Dynamical Interactions with Unseen Planetary Mass Companions Were Spatially Resolved and Imaged Around Three Young (< 10 Myr) Stars. HR 4796A (A0V), ~ 8 Myr A 70AU radius ring, ~ 10 AU wide ring of very red material, exhibiting strong forward scattering and ansally asymmetric hemispheric flux densities.

Dusty Disks with Radial and Hemispheric Brightness Anisotropies and Complex Morphologies, Possibly Indicative of Dynamical Interactions with Unseen Planetary Mass Companions Were Spatially Resolved and Imaged Around Three Young (< 10 Myr) Stars. A 400AU radius disk, with a broad, partially filled asymmetric gap containing a “spiral” arclet. HD A (Herbig Ae/Be) ~ 5 Myr

Dusty Disks with Radial and Hemispheric Brightness Anisotropies and Complex Morphologies, Possibly Indicative of Dynamical Interactions with Unseen Planetary Mass Companions Were Spatially Resolved and Imaged Around Three Young (< 10 Myr) Stars. TW Hya (K7) “Old” PMS Star Pole-on circularly symmetric disk with a break in its surface brightness profile at 120 AU (2”).

Dusty Disks with Radial and Hemispheric Brightness Anisotropies and Complex Morphologies, Possibly Indicative of Dynamical Interactions with Unseen Planetary Mass Companions Were Spatially Resolved and Imaged Around Three Young (< 10 Myr) Stars. TW Hya (K7) “Old” PMS Star and, possibly, a radially and azimuthally confined arc-like depression. Pole-on circularly symmetric disk with a break in its surface brightness profile at 120 AU (2”).

HR 4796A

HR 4796A - Observational Chronology
Jura (ApJ, 383, L79) inferred presence of large amount of circumstellar dust from IRAS excess. Estimated tdust = Ldisk/Lstar = 5x10-3 (~2x b Pictoris). Jura et al. (ApJ, 445, 451) noted earlier 110K estimate of dust temperature indicated lack of material at < 40 AU. Required grains > 3mm to be bound gravitationally at 40<r<200 AU. No close companions with M* > Msun seen (speckle). Koerner et al. (ApJ, 503, L83) and Jayawardhana et al. (ApJ, 503, 79) independently image mid-IR disk. Inner depleted region evident in high resolution 20.8mm image reproduced with a model suggesting: i=72° (+6°, -9°), PA = 28°±6°, Rin ~ 55AU, Rout ~ 80AU -> Kuiper belt-like dust ring. Schneider et al. (ApJ, 513, L127) report on morphology and photometry of well-resolved NIR images in two NIR colors (1.1 and 1.6mm) of a narrowly confined ringlike circumstellar disk, with characteristic properties predicted by Koerner et al, from ~ 0.1" resolution NICMOS coronagraphy obtained contemporaneously with 1998 mid-IR images. Koerner et al. (1998) Observation Model 2" m 20.8 Schneider et al. (1999)

HR 4796A - Has an M-Dwarf Companion
E B A 2" AB = 7.7" ≥500 pc HR 4796B (late M) Likely PMS Star H b , H g , Ca H&K emission J-H = 0.75 … which could help to truncate the outer portion of the disk

NICMOS Observations of the HR 4796A Circumstellar Debris Ring
GEOMETRY PA = 26.8°±0.6° i = 73.1°±1.2° a = 1.05”±0.02” E N 20 40 60 80 100 Arc Seconds (Y) -1.0 -0.5 0.0 0.5 1.0 1.5 1.0 0.5 -1.5 Arc Seconds (X) F160W F110W mJy/pixel MORPHOLOGY r = 70AU width < 14AU “abrupt” truncation r < 50 AU FLUX DENSITY 1.1mm 1.6mm H(F160W) = 12.35± J(F110W) = 12.92±0.08 Tdust ~ Ldisk/L* 1.1mm 1.6mm NIR scattered flux in good agreement with visible absorption & mid-IR re-radiation.

NICMOS Observations of the HR 4796A Circumstellar Debris Ring
20 40 60 80 100 Arc Seconds (Y) -1.0 -0.5 0.0 0.5 1.0 1.5 1.0 0.5 -1.5 Arc Seconds (X) F160W F110W mJy/pixel Anisotropies NE ansa ~ 15% brighter than SW ansa. Suggestion of preferential (forward) scattering to SE. Implications Possible dynamical confinement of particles by one or more unseen bodies. Mean particle size > few mm. debris origin, not I.S. dust.

HR 4796A - Thermal IR Imaging
Deep OSCIR images of the HR 4796A disk Telesco et al. (1999, A&A) indicate comparable sizes of and 18.2 mm emitting regions. They find tcentral zone ≤ 3% of main part of the disk (confirming that the central hole is largely cleared). Inward fall-off from the ring is shallower at 18.2mm then inferred from the NICMOS images. Moreover, they report on a possible brightness asymmetry in the OSCIR images (similar to NICMOS) which might implicate the existence of a gravitational perturber causing this "pericenter glow" (Wyatt, et al 2000) from particles in the NE side of the disk shifted closer to the star. Top: OSCIR 18.2 m m Bottom: NICMOS 1.1 m m Star-subtracted scans along the disk major axis. 1.0 0.5 N N 0.0 E E -0.5 Models for different grain -1.0 sizes (Telesco, et al. 1999) 20 40 60 80 100 20 40 60 80 100 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 Arc Seconds

HR 4796A - Observational Chronology
Greaves et al. obtain JCMT/SCUBA 450 and 850mm flux excess measures of 0.18 and Jy, respectively, and estimate total gas mass < 1–7 Earth masses. Augereau et al. re-reduce K' observations of Mouillet et al. and find excess in agreement with Schneider et al at ~1" in low S/N image showing extension in NE/SW directions. They estimate a lower limit for dust mass of ~ 4 Earth masses. NICMOS Additional processing recovered ring flux closer in and suggested somewhat higher inclination (~76°). “Clumpiness” due to residuals in PSF subtraction, not attributed to structure of ring.

HR 4796A - Kenyon & Wood (2000) Dynamical Evolutionary Model
Monte Carlo runs constrain geometry & Kenyon & Luu (1999, ApJ) t dust Produce observed dust distibution in 10 Myr a e = 10 -3 m MMSN Minitial: 10-20x minimum-mass solar nebula Assume: isotropic scattering and, w = 0.3 (Augereau et al, 1999) Adust to obtain t ~ 1.5x10 -3 z=0.5AU, R=5AU, tw NIR =0.25 z=5AU, R=10AU, =0.2 z=1AU, R=20AU, =0.1 NICMOS 1.1 m m image CONCLUSIONS: • Planet 70 AU in 10 Myr possible with initial disk mass =10—20M . MMSN • Dust production associated with planet formation is then confined to a ring with D a = 7—15 AU. • Optical depth in ring satisfies constraints on scattered light at 1—2 m m and on thermal emission at 10—100 m m if the dust size distribution is N ~ r -q with q ≥ 3 for r ≤ 1 m. i i • Models with disk masses smaller than 10 fail to MMSN produce planets and an observable dusty ring in 10 Myr.

HR 4796A - Augereau et al. (1999) Physical Model
Two-component model reproduces all then-available observations: "the full spectral energy distribution from the mid-infrared to the millimeter wavelengths, resolved scattered light and thermal emission observations". a) cold amorphous (Si and H20 ice) grains > 10mm in size (cut-off in size by radiation pressure), with porosity ~0.6, peaking at 70AU. b) hot dust at ~ 9AU of "comet-like" composition (crysatlline Si and H20), porosity ~ 0.97. Collisions are common in both populations. Bodies as large as a few meters are required. Model gives rise to a minimum mass of a few Mearth with gas:dust < 1. S i m u l a t e d d i s k a t 2 . 8 m m , a s s u m i n g g r a i n p r o p e r t i e s a n d s u r f a c e d e n s i t y d e r i v e d f r o m ~0.2Jy t h e S E D f i t t i n g a n d a b P i c l i k e v e r t i c a l s t r u c t u r e , w i t h . 1 4 " p i x e l s l i k e o b s e r v a t i o n s b y K o e r n e r e t a l . ( 1 9 9 8 ) a n d cold annulus+hot dust Cold annulus + hot dust (~0.2Jy) convolved 10m telescope PSF. S i m u l a t e d g s o f h c n p k 7 A U r 1 . ( w 6 " x N I C M O ) y H - G T b v | < 5 > 2 J , with HST. Full SED fitting with two dust populations.

The quest for higher resolution
HR 4796A The quest for higher resolution

STIS Observations of the HR 4796A Circumstellar Debris Ring
Orient # Orient #2 HR 4796A DOrient = 16° HR 4748 (PSF)

+ _ STIS Observations of the HR 4796A Circumstellar Debris Ring
Orient # Orient #2 + _ HR 4796A HR 4748 (PSF)

Better Focus Match Better Position Match Better Position Match Better
STIS Observations of the HR 4796A Circumstellar Debris Ring PSF Orient #1 PSF Orient #2 Better Focus Match Better Position Match Better Position Match Better Focus Match Varience Minimized (Flux & Position Adjusted) PSF Subtractions

2-rolls samples regions otherwise obscured by wedge & spikes
STIS Observations of the HR 4796A Circumstellar Debris Ring PSF Orient #1 PSF Orient #2 2-rolls samples regions otherwise obscured by wedge & spikes N E Varience Minimized (Flux & Position Adjusted) PSF Subtractions

STIS Observations of the HR 4796A Circumstellar Debris Ring
Weighted Image Combination - Resampled

(Least-Squares Isophotal Ellipse Fit)
HR 4796A RING GEOMETRY (Least-Squares Isophotal Ellipse Fit) Ansal Separation (Peaks) = ” ± ” Major Axis of BFE = ” ± " P.A. of Major Axis (E of N) = 27.06° ± 0.18° Major:Minor Axial Length = ( ± 0.034): 1 Inclination of Pole to LOS = 75.73° ± 0.12° Photocentric Offset from BFE(Y) = " ± " Photocentric Offset from BFE(X) = " ± "

HR 4796A Circumstellar Debris Ring - WIDTH
WIDTH AT NE ANSA FWHM: 12.9±0.7AU % Dring * Slightly asymmetric 1-e-1: 7.5±0.4AU 11.9% Rring Brightness (Normalized to NE Ansa) Measured = 0.197” PSF point source = 0.043” FWHM ring = 0.192” 1-e = 0.126”

RING GEOMETRY - Least-Squares Isophotal Ellipse Fit
Ansal Separation (Peaks) = ” ± ” Major Axis of BFE = ” ± " P.A. of Major Axis (E of N) = 27.06° ± 0.18° Major:Minor Axial Length = ( ± 0.034): 1 Inclination of Pole to LOS = 75.73° ± 0.12° Photocentric Offset from BFE(Y) = " ± " Photocentric Offset from BFE(X) = " ± "

“FACE-ON” PROJECTION - With Flux Conservation

Spatially Resolved Relative PHOTOMETRY of the Ring

Photometric Error Estimation

NW:SE Surface Brightness Anisotropy
N-Sigma Brightness Ratio (Percent)

Front:Back Surface Brightness Anisotropy
N-Sigma Brightness Ratio (Percent)

Aperture Photometry STIS(leff 0.58 mm): F(ring[unobscured])/F(star) = ± (7.3%) NICMOS (leff 1.10 mm): F(ring[unobscured])/F(star) = ± (14.3%) NICMOS (leff 1.60 mm): F(ring[unobscured])/F(star) = ± (20.8%)

Wavelength Dependent Scattering Efficiency (Color)

HR 4796A SUMMARY Ring geometry/astrometry defined by NICMOS improved by higher resolution STIS observations. Notably, i 2.6° larger than original (published) NICMOS solution. Spatially resolved photometry of ring with ±2% uncertainty at ansae (1”), and ±6—8% uncertainty at 0.6—0.5”. Characteristic width ~ 10% of 70AU radius ring. “Left/Right” brightness anisotropy or ~20% along at least 50° wide diametrically opposed arcs centered on ansae. “Front/Back” brightness anisotropy, roughly symmetric in both L/R “hemispheres”, increasing with longitudinal distance from ansae to 35% difference at 30° from ansae. Ring is uniformly RED from “V” to H with 1:1.7:2.9 spectral reflectance in CCD50(“V”):F110W(1.1mm):F160W(H).

Brightness Anisotropies, Confinement & Color
Consistent with Dynamical Interactions with Co-Orbital Unseen Planet-Mass Bodies

HD 141569A - Thermal IR Disk Detected/Imaged by Silverstone
HD PSF STAR B9V Herbig Ae/Be Star, H = 6.89 d = 100 pc, Age ~ 5 Myr, 2.3Msun 1" 12.5 0.26" FWHM 17.9 0.37" FWHM 20.8 0.43" FWHM

HD 141569A - NICMOS Coronagraphic Imaging
Disk Radius = 400 AU Gap Radius = 245 AU Gap Width ~ 40 AU 1.1 m m NICMOS Coronagraphic Image 1" Face-on Projection Unsharp Masking Gradient Enhancement Scattering by cold dust is OUTSIDE region of thermal emission.

HD 141569A - Circumstellar Disk & Gap
Surface Density of Scatterers 100 200 300 400 500 Radius (AU) 0.01 x tw 500AU (5") NICMOS F110W HD A - Circumstellar Disk & Gap Total Flux Density = r>0.6” Peak SB = 0.3mJy 185AU Inclination to LOS = 51°±3° Intrinsic Scattering Function results in Brightness Anisotropy in ratio 1.5±0.2:1 in direction of forward scattering. Gap may be partially cleared of material by unseen planetary companion. Gap Width:Radius implies planetary mass of ~ 1.2 M jup (2Mjup detection gap, where w=0.35±0.05). Hieracrchial triple system dA(BC) = 8.3”, dBC = 1.3” (projected) M-Dwarf companions may influence disk dynamics.

D E N S I T Y O F S C A T T E R E R S t w = 4 p r F ( r ) w = a l b e
HD A - Albedo of the Grains D E N S I T Y O F S C A T T E R E R S t w = 4 p r 2 F ( r ) w = a l b e d o t = o p t i c a l d e p t h t o s c a t t e r i n g t = t + t t o t a l s c a t t e r e d a b s o r b e d I f t s c a e r d + b o = L R / 8 . 4 x 1 - 3 , h n w l 2 5 * B u t , i n t h e o u t e r p o r t i o n o f d i s k : t < 8 . 4 x 1 - 3 = = > w ~ . 4 a b s o r b e d s c a t t e r e d (Weinberger, et al., 1999)

HD 141569A - Can a Planet “Hide” in the Gap?
o c a t i n f g p 6 R = 240 AU, M = 2.3Msun, so P = 2450 yr. For Age = 5x10 -> 2000 orbits Limiting F110W magnitude for a point source in the gap is > M ~ 3 jup Mass of Planet to Clear Gap: M/M ~ c( D a/a 3 ) where c~ 0.1 (Lissauer 1993) * for D a = 50 AU, a = 240 AU -> M = 0.9 M , below detection threshold. jup N o t e : F o r a g a s e o u s d i s k ( n o t t h i s c a s e ) t i m e t o c l e a r g a p ~ 3 o r b i t s ( L i n e t a l 1 9 9 9 ) .

HD 141569 (A, BC)- A Triple System
Differential 1998 NICMOS Proper Motions 1934 Rossiter v A – B 8 S e p = 7 . ” 5 7 7 P A = 3 1 1 . 5 6 v B – C 5 Arcseconds (North) S e p = 1 . ” 3 8 4 3 P A = 3 1 . 9 2 1 1 2 3 4 5 6 7 8 Arcseconds (West) Predicted 1998 position from 1934 measures and Hipparcos proper motions Also, consistent radial velocities ==> Common Space Motion (Weinberger, et al, 2000, ApJ)

HD 141569 B & C ~ 5 Myr ± 3 HD 141569 (A, BC)- Age-Dating the System
L i I 10 T i O Flux Density (x10 B 5 A 6400 6600 6800 7000 7200 7400 . 5 - 1 7 C B L i H a E W Spectral Types: B = M2V, C= M4V Companions: Young, Hot, M-Dwarfs

HD 141569 (A, BC) - Dynamical Sculpting by Companions?
2 3 4 5 6 7 8 9 • Density of Scatters: Equal at 200 AU and 360 AU. If non-coplaner companions can excite vertical velocities in disk. • Circular 50 AU-wide 250AU Continual clearing to remove P-R and RP driven transiting particles. • Gap circularity implies dynamical stability on long time-scales. • If co-planer Lindblad resonances from 1053AU distant CoM (BC) 243 AU, 263AU closest to gap.

HD 141569A NICMOS (0.11” Resolution)
Knowing the Flux Desnisity, Orientation, Size, etc., Allowed Planning an Effective Follow-up...

HD 141569A STIS (0.05” Resolution)
Global strcture better described by “concentric ring” morphology. “Gap” broader and partially filled. “Spiral arclett” structure seen in disk gap.

HD 141569A NICMOS (0.11”) STIS (0.05” ) Gradient Enhancement
+ Mild Smoothing Pixel Scale) Gradient Enhancement

TW Hydrae

TW Hydrae • K7Ve (Rucinski & Krautter, 1983)
• Distance: 56±7 pc (Hipparchos) • Age: ~ 6 Myr • Ha and UV Excesses Isolated Classical T-Tauri Star • Member TW Hya Association (TWA ~ 10 Myr, 60 pc) • Long Wavelength Excesses t ~ L disk /L star ~ 0.3 (IRAS) CO emission (Zuckerman et al. 1995)

TW Hydrae - NICMOS Coronagraphic Imaging
Face-On, Optically Thick, 190 AU radius Flared Disk Flared Disk + Hole 1.1 m m 1.6 m m ln Surface Brightness (mJy arcsec -2 ) • Gray scattering: F110W - F160W = 0.96 mag (same as star) Thin Disk

TW Hydrae - Is it Real? SURFACE BRIGHTNESS (mJy arcsec-2) YES

TW Hydrae - Is it Real? YES STIS (0.5mm) WFPC-2 (0.8mm)
Also seen in HST Optical Band-Passes STIS (0.5mm) WFPC-2 (0.8mm) YES

TW Hydrae - Surface Brightness Profile
Flux density Power Law: r-2.6±.0.1 @ 35 AU < r < 135 AU 100 AU

TW Hydrae - Surface Brightness Profile
“Zone 2-3 Break” may implicate sculpting by grains Surface Brightness (mag arcsec-2) 12 14 16 18 20 22 0.6 0.8 1 3 2 4 Radius (Arc Seconds) F160W F110W F814W F606W 50CCD ( uncalibrated ) Zone NICMOS - Weinberger et al. 1999 WFPC-2 Krist 2000

TW Hydrae - Optical Assymetry
Radially and azimuthally confined arc-like depression?

TW Hydrae - Companion Detection Limits
ABSOLUTE MAGNITUDE

TW Hydrae - Mid-IR (8—13mm) Spectrum
(Spatially & 17.9 mm) Peak: Amorphous (~9.6mm) & Crystaline (~11.2mm) Silicates. Fn (Jy) Keck I LWS Dl/l ~ 120 Weinberger, Becklin, Schneider, 2001 Wavelength (microns)

TW Hydrae - SED Model from All Spectral Bands
ala Chaing et al. (2001) Surface grains < 2mm Interior grains < 12mm Grain Size Distribution dN/dr (interior) ~ r-1 dN/dr (surface) ~ r-3.5 Dust Surface Mass Density 10 (r/AU) -1 cm-2 Disk Radii: Inner = AU Outer = 200 AU Log lFl [erg s-1 cm-2] Wavelength [microns]

TW Hydrae - Summary TTS surrounded by Optically Thick dust disk.
Disk must be Flared given scattered light radius and thermal SED. “Break” in Surf. ~ 95AU may be due to dynamical effects. No Companions found to 10—2 40—100 AU limit. Disk Mass: ~ few x102 Earth Masses of Condensed Silicates & Ices. Dust mass few times > “typical” Taurus & Ophiuchus TTS Disks. Good evidence for grain growth within the disk.

PHYSICAL SIZES

The first-epoch NICMOS mission ended on 4 January 1999
The first-epoch NICMOS mission ended on 4 January But, just as dust is reprocessed around young stars, NICMOS will get a new lease on life after HST SM3B (14 Feb 2002) when a a reverse Brayton cycle cooler will be installed and interfaced with NICMOS, returning it to service. We look forward to the re-incarnation of NICMOS, to continue the search. Today, we have only a handful of spatially resolved images of dusty debris disks and extra-solar planet companion candiates.

GLENN SCHNEIDER NICMOS Project Steward Observatory 933 N. Cherry Avenue University of Arizona Tucson, Arizona 85721 Phone: FAX:

Dust Busters: When Worldletts Collide

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