The connection between inner and outer debris disks probed by infrared interferometry

Olivier Absil University of Liège

From Atoms to Pebbles – Herschel’s view of Star and Planet Formation Grenoble, 22 March 2012

T

HE CONNECTION BETWEEN INNER AND OUTER

DEBRIS DISKS PROBED BY INFRARED

Lisse et al. 2012

I

NNER VS

.

OUTER DEBRIS DISK

T ~ 40 K

T > 300 K

Prominent far-IR excess Easy to resolve (>1”)

Small near/mid-IR excess Difficult to resolve (< 0.1”) wavelength fl u x

???

I

NFRARED INTERFEROMETRY MAY HELP

Disk larger than angular resolution (λ/B) incoherent flux

Induces a visibility drop at all baselines

Best detected at short baselines (~10-30m)

Flux ratio

Requires very good accuracy (<1%)

~ 40 mas resolved at 10m

Resolved at 200m

H

IGH PRECISION INTERFEROMETERS

FLUOR at CHARA (IONIC at IOTA)

V

EGA VIEWED BY

CHARA/FLUOR

R

ADIATIVE TRANSFER MODELING

H- and K-band interferometry (CHARA/FLUOR, IOTA/IONIC) N-band nulling interferometry (MMT/BLINC)

Archival near- to mid-IR spectro-photometry

Bayesian χ

_{analysis of}

large parameter space

Presence of carbons ≥ 10% Distance: ~ 0.1 – 0.5 AU Steep density power law: α < −3 ring?

Mass: ~2×10

_M

Earth

Luminosity: ~5×10

_L

M

OST PROBABLE DUST PROPERTIES

Defrère et al. 2011

N

EXT STEP

:

LOW

-

RESOLUTION SPECTRA

Dispersed fringes with PIONIER (soon FLUOR)

Flux ratio measurements across H and/or K band

Direct constraint on dust temperature

O

RIGIN OF HOT DUST

:

STEADY STATE

?

Local production?

Connection to outer disk?

Multiple scattering of comets?

0.5 AU 100 AU

S

TEADY STATE MULTIPLE SCATTERING

Requires 3+ planets and 10

M

in cold reservoir

O

RIGIN OF HOT DUST

:

TRANSIENT

?

Isolated event?

Large collision (e.g. Earth-Moon) Break-up of giant comet

Dynamical perturbations?

• Asteroid belt disturbed by

MMR with massive planet

Late Heavy Bombardment

• Global rearrangement

D

EBRIS DISK SURVEY AT

CHARA/FLUOR

Magnitude-limited sample (K < 4)

“Unbiased” control sample: 25 stars w/o cold dust

Observed most stars, ~42 of sufficient quality

One surprise: companion to epsilon Cephei

Mawet et al. 2011

37% 16% 0% 10% 20% 30% 40% 50% 60% A FG E x o zo d i d e te ct io n f re q u e n cy

Cold dust (Spitzer/MIPS24+70)

P

RELIMINARY STATISTICS VS

.

SPECTRAL TYPE

Many more K-band excesses than anticipated!

A-type stars more prone to hot dust

Same trend as in cold disks, frequency compatible Suggests that they could be related (scattering?)

38% 21% 27% 0% 10% 20% 30% 40% 50% 60% A F GK E x o zo d i d e te ct io n f re q u e n cy

Hot dust (Absil et al., in prep)

30% 26% 33% 20% 25% 16% 19% 0% 10% 20% 30% 40% 50% 60% A F G K E x o zo d i d e te ct io n f re q u e n cy DEBRIS DUNES

P

RELIMINARY STATISTICS VS

.

COLD DUST

No correlation with cold dust reservoirs

Suggests transient event rather than steady state

32% 25% 0% 5% 10% 15% 20% 25% 30% 35% 40% 45%

Cold dust No cold dust

E x o zo d i d e te ct io n f re q u e n cy

P

ERSPECTIVES

EXOZODI project

Extend survey to confirm statistics

(goal: 200 stars)

North: refurbished FLUOR at CHARA

South: PIONIER at VLTI (Le Bouquin et al. )

Investigate age dependence

Follow up detections

Discriminate with potential binaries

Multi-color information for SED modeling

Search for variability

Improve models (RT, dynamics, collisions)

EXOZODI team - Augereau (PI) - Thébault (Co-PI) - Absil - Beust - Bonsor - Coudé du Foresto - Defrère - Ertel - Kral - Lebreton - Le Bouquin - Marbeuf - … 59