Glenn Schneider Steward Observatory, University of Arizona (NICMOS/IDT) Dusty Circumstellar Disks and Substellar Companions

Glenn Schneider Steward Observatory, University of Arizona (NICMOS/IDT) Substellar Companions and Dusty Circumstellar Disks … and, what’s ~ 100 ~ 100 AU?

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

H-Band (F160W) Point-Source Detectability Limits Two-Roll Coronagraphic PSF Subtraction 22m Total Integration  H(5  ) =  ”  ” 2.  Read Noise DominatedPhoton Noise Dominated H=6.9

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

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. 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. BROWN DWARF/ VLM Star Candidates: 32 HighProper Motion Late M-Dwarf Stars within ~ 10 pc.

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. few megayears to a few tens of megayears 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.

Collapsing protostar forms proto- planetary disk Rocky cores of giant planets form Terrestrial planets form Clearing of inner solar system, formation of a Kuiper cometary belt? 10 6 yrs 10 8 yrs 10 9 yrs accrete gaseous atmospheres Era of heavy bombarment by comets Current age of the Sun: 5x10 9 yrs.  Persei Sun TW Hydrae Taurus, Ophiuchus star forming regions Hyades Tucanae Assoc Pleiades Primary Dust (≤  m) Secondary Dust (≥  m) Locked to Gas Collisional erosion Clearing Timescales: P-R drag few 10 6 Rad. Pressure: ~ 10 4 rys 10 7 Assoc Giant planets From: R. Webb Planet-Building Timeline

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

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

CORONAGRAPHICCOMPANIONDETECTION 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  Roll = 30°  Time = 20 minutes

Above: Coronagraphic Images  Roll: 30° Above: Coronagraphic Images  Roll: 30° Left: Difference Image Same display dynamic range At  =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  H = 13.2

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

PositiveImageExtracion

NegativeImageExtraction(Inverted)

RotateNegativeExtractionAboutOccultedTarget And Add AfterInversion

Model and RemoveDiffractionSpikeResiduals**DSPK Is it a Point Source?

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

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 (  ) Dependence via Model PSF Implantation (  ) Dependence via Model PSF Implantation Observed Model * Nulled Implant * TinyTim 5.0 HST+NICMOS Optical Model - Krist

Detectability: (  ) Dependence via Model PSF Implantation

% Recovered Flux S/N (Positive Implant Only) Photometric Efficacy & Statistical Significance

TWA6B Detection Illustrates Performance Repeatability Two-Roll Coronagraphic PSF Subtraction 22m Total Integration  H(5  ) =  ”  ” 2. 

TW Hya Assn K7 primary, D = 55pc Age = 10 Myr  =2.54”, 140AU  H =13.2 (L B/A )[H]=5 x Habs = 16.6 Implies: Mass ~ 2 Jupiter Mass ~ 2 Jupiter T eff ~ 800K T eff ~ 800K IF Companion... S/N TWA6B = 35 TWA 6A/B

A Jovian > 140 AU? RV Surveys suggest ~ 5% MS * s have 0.8—8 Mjup 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 0.9  m 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 1.40— NICMOS/C2 F090M 0.80—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 0.9  m 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 Keck/AO Astrometric (PM) Follow-up Thus-Far Inconclusive * Sudarsky et al., 2000Spectrum from A. Burrows

Is it, or Isn’t It? We have requested 12 HST Orbits to attempt PSF-subtracted NICMOS G141 (1.1—1.9  m) grism spectrophotometry to obtain what might be the first spectrum of an extra-solar planet >23.1 ~25.4 >27.2 This observation will also yield a Differential Proper Motion Measure.

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.

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. 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  Pictoris remained the only such disk imaged.  Pictoris Resolved imaging spatial distribution of dust/debris. Direct (Scattered Light) Imaging of Dusty Debris

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 Pole-on circularly symmetric disk with a break in its surface brightness profile at 120 AU (2”). and, possibly, a radially and azimuthally confined arc-like depression.

HR 4796A

Jura (ApJ, 383, L79) inferred presence of large amount of circumstellar dust from IRAS excess. Estimated  dust = Ldisk/Lstar = 5x10-3 (~2x  Pictoris) Jura et al. (ApJ, 445, 451) noted earlier 110K estimate of dust temperature indicated lack of material at 3  m to be bound gravitationally at 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 20.8  m 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 1.6  m) 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  m Schneider et al. (1999) HR 4796A - Observational Chronology

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

NICMOS Observations of the HR 4796A Circumstellar Debris Ring E N Arc Seconds (Y) Arc Seconds (X) E N F160W F110W mJy/pixel GEOMETRY PA = 26.8°±0.6° i = 73.1°±1.2° a = 1.05”±0.02” MORPHOLOGY r = 70AU width < 14AU “abrupt” truncation r < 50 AU FLUX DENSITY 1.1  m 1.6  m H(F160W) = 12.35± J(F110W) = 12.92± T dust ~ L disk /L * 1.4±0.2x  m 2.4±0.5x  m NIR scattered flux in good agreement with visible absorption & mid-IR re-radiation.

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

Deep OSCIR images of the HR 4796A disk Telesco et al. (1999, A&A) indicate comparable sizes of 10.8 and 18.2  m emitting regions. They find  central 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 18.2  m 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 E N Arc Seconds E N Top: OSCIR 18.2  m Bottom: NICMOS 1.1  m Star-subtracted scans along the disk major axis. Models for different grain sizes (Telesco, et al. 1999) HR 4796A - Thermal IR Imaging

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 Greaves et al. obtain JCMT/SCUBA 450 and 850  m 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. HR 4796A - Observational Chronology

z=0.5AU, R=5AU,  NIR =0.25 z=5AU, R=10AU,  NIR =0.2 z=1AU, R=20AU,  NIR =0.1 NICMOS 1.1  m image Monte Carlo runs constrain geometry &  dust Produce observed dust distibution in 10 Myr Minitial: 10-20x minimum-mass solar nebula Assume: isotropic scattering and,  = 0.3 (Augereau et al, 1999) Adust to obtain  ~ 1.5x10 -3 a e 0 = e 0 = m 0 = 10 MMSN 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  a = 7—15 AU. Optical depth in ring satisfies constraints on scattered light at 1—2  m and on thermal emission at 10—100  m if the dust size distribution is N ~ r i with q ≥ 3 for r i ≤ 1 m. Models with disk masses smaller than 10 MMSN fail to produce planets and an observable dusty ring in 10 Myr. -q Kenyon & Luu (1999, ApJ) HR 4796A - Kenyon & Wood (2000) Dynamical Evolutionary Model

Cold annulus + hot dust (~0.2Jy) Simulated disk at 20.8  m, assuming grain properties and surface density derived from the SED fitting and a  Pic like vertical structure, with 0.14" pixels like observations by Koerner et al. (1998) and convolved 10m telescope PSF. Full SED fitting with two dust populations. HR 4796A - Augereau et al. (1999) Physical Model Simulatated images of the cold annulus peaked at 70 AU in scattered light at 1.1  m (with 0.076" pixels as in NICMOS) for two asymmetry factors considered assuming a Henyey- Greenstein phase function (The inner hot dust not observable has not been added). The NICMOS observation suggests |g| < The flux density predicted in the region outside r > 0.65" is 5.2mJy, in good agreement with the 7.5±0.5mJy observed with HST. 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 > 10  m 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 ~ 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. ~0.2Jy cold annulus+hot dust

HR 4796A The quest for higher resolution

HR 4796A HR 4748 (PSF) Orient #1 Orient #2  Orient = 16° STIS Observations of the HR 4796A Circumstellar Debris Ring

HR 4796A HR 4748 (PSF) Orient #1 Orient #2 __ STIS Observations of the HR 4796A Circumstellar Debris Ring

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

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

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

Ansal Separation (Peaks) = 2.107” ± ” Major Axis of BFE = 2.114” ± " 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 RING GEOMETRY (Least-Squares Isophotal Ellipse Fit)

Brightness (Normalized to NE Ansa) HR 4796A Circumstellar Debris Ring - WIDTH FWHM ring = 0.192” FWHM: 12.9±0.7AU 9.6% D ring 1-e -1 = 0.126” PSF point source = 0.043” Measured = 0.197” WIDTH AT NE ANSA 1-e -1 : 7.5±0.4AU 11.9% R ring * Slightly asymmetric *

Ansal Separation (Peaks) = 2.107” ± ” Major Axis of BFE = 2.114” ± " 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) = " ± " RING GEOMETRY - Least-Squares Isophotal Ellipse Fit

“FACE-ON” PROJECTION - With Flux Conservation

Spatially Resolved Relative PHOTOMETRY of the Ring

Photometric Error Estimation

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

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

STIS( eff 0.58  m): F(ring[unobscured])/F(star) = ± (7.3%) NICMOS ( eff 1.10  m): F(ring[unobscured])/F(star) = ± (14.3%) Aperture Photometry NICMOS ( eff 1.60  m): 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. “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. Characteristic width ~ 10% of 70AU radius ring. Ring is uniformly RED from “V” to H with 1:1.7:2.9 spectral reflectance in CCD50(“V”):F110W(1.1  m):F160W(H). Spatially resolved photometry of ring with ±2% uncertainty at ansae (1”), and ±6—8% uncertainty at 0.6—0.5”.

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

HD A

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

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

Surface Density of Scatterers Radius (AU) 0.01 x  500AU (5") NICMOS F110W HD A - Circumstellar Disk & Gap Total Flux Density = r>0.6” Peak SB = 0.3mJy arcsec 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 d A ( BC ) = 8.3”, d BC = 1.3” (projected) M-Dwarf companions may influence disk dynamics.

DENSITY OF SCATTERERS  = 4  r 2 F(r)  = albedo  = optical depth to scattering But, in the outer portion of disk:  absorbed < 8.4x10 -3 ==>  scattered ~ 0.4  total  =  scattered +  absorbed If  scattered +  absorbed = L IR /L = 8.4x10 -3, then  scattered =  scattered /  total = 0.25 * (Weinberger, et al., 1999) HD A - Albedo of the Grains

Location of gap R = 240 AU, M = 2.3Msun, so P = 2450 yr. For Age = 5x10 6 -> 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(  a/a 3 ) where c~ 0.1 (Lissauer 1993) for  a = 50 AU, a = 240 AU ->M = 0.9 M jup, below detection threshold. Note: For a gaseous disk (not this case) time to clear gap ~ 300 orbits (Lin et al 1999). HD A - Can a Planet “Hide” in the Gap?

 A – B Sep = 7.”57 PA = 311.5°  B – C Sep = 1.”38 PA = 301.9° 1998 NICMOS 1934 Rossiter Differential Proper Motions Arcseconds (West) Arcseconds (North) Predicted 1998 position from 1934 measures and Hipparcos proper motions Also, consistent radial velocities ==> Common Space Motion (Weinberger, et al, 2000, ApJ) HD (A, BC)- A Triple System

TiO LiI H  Flux Density (x10 3 ) B A 0.50 ± ± 0.05 C 0.50 ± ± 0.05 B Li H  EW HD B & C ~ 5 Myr ± 3 Spectral Types: B = M2V, C= M4V Companions: Young, Hot, M-Dwarfs HD (A, BC)- Age-Dating the System

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 (A, BC) - Dynamical Sculpting by Companions?

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

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

TW Hydrae

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

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

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

YES Also seen in HST Optical Band-Passes STIS (0.5  m)WFPC-2 (0.8  m)

TW Hydrae - Surface Brightness Profile Flux density Power Law: r 35 AU < r < 135 AU 100 AU

TW Hydrae - Surface Brightness Profile “Zone 2-3 Break” may implicate sculpting by grains

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

ABSOLUTE MAGNITUDE TW Hydrae - Companion Detection Limits

Peak: Amorphous (~9.6  m) & Crystaline (~11.2  m) Silicates. TW Hydrae - Mid-IR (8—13  m) Spectrum (Spatially & 17.9  m) Wavelength (microns) F (Jy) Keck I LWS  ~ 120 Weinberger, Becklin, Schneider, 2001

Log F [erg s -1 cm -2 ] Wavelength [microns] TW Hydrae - SED Model from All Spectral Bands ala Chaing et al. (2001) Surface grains < 2  m 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 = 0.05 AU Outer = 200 AU

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 M 40—100 AU limit. Disk Mass: ~ few x10 2 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 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 Phone: FAX: