Polluted White Dwarf Science with Hubble and JWST

Siyi Xu (许偲艺) ESO Fellow

White Dwarf

H/He Atom Heavy Atom

About 25% WDs are polluted ~2000

10-3 AU

Roche Limit 1987

Infrared Excess

Dust Sublimation

Credit: NASA/JPL-Caltech

Spectroscopy of WD atmosphere à chemical compositions of extrasolar minor planets

Extrasolar rocky material mostly resembles the composition of bulk Earth.

Xu, Jura, & Koester et al. 2014

Mg, Ca from Keck/HIRES C, N, O, S, Fe, Ni from HST/COS

Xu, Zuckerman, & Dufour et al., 2017

Comet Halley Analog

•  MIRI/LRS: 5-12 micron, R~40-160

•  MIRI/MRS: 5-30 micron, R~1500-3500

JWST: Mineral Compositions of Planetary Debris

Emiss

ivity

= O

bser

ved

/ Bν(

930

K)

Wavelength (μm)

am. carbon

carbonatesPAHwater vap.

water ice

sulfidesphyllosilicates

cryst. pyr.

am. silicates

cryst. forsterite

5 10 30 3515 20 25

0.0

0.5

1.0

From Spitzer/IRS Reach, Lisse, von Hippel, & Mullally 2009

Take Home Message

#1. JWST will return the mineral compositions of extrasolar minor planets

White Dwarf

H/He Atom Heavy Atom

About 25% WDs are polluted ~2000

10-3 AU

Roche Limit 1987

Infrared Excess

Dust Sublimation

a disintegrating asteroid 2015

Vanderburg, Johnson, & Rappaport et al., 2015

WD 1145+017: Multiple Objects with ~4.5 hour Period K2

FLWO

0.6

0.7

0.8

0.9

1 A1 A2 B A1

Rel

ativ

e fl

ux

u'

g'

i'

0 50 100 150 200 250 300 350

t [min]

-0.1-0.05

00.05

u'-i'

-0.1-0.05

00.05

u'-g'

-0.1-0.05

00.05

g'-i'

0.6

0.7

0.8

0.9

1 A1 A2 B A1

Rel

ativ

e fl

ux

u'

g'

i'

0 50 100 150 200 250 300 350

t [min]

-0.1-0.05

00.05

u'-i'

-0.1-0.05

00.05

u'-g'

-0.1-0.05

00.05

g'-i'

ULTRACAM

Hallakoun, Xu, & Maoz, et al. submitted

A Cartoon Illusion of WD 1145+017 system

Search for more WD 1145+017 like system: -  K2 Mission -  Ground-based photometric surveys -  TESS Mission

JWST Follow Ups

• NIRCam: Imaging & Time-Series Imaging • “WD 1145+017 like systems”: high quality

infrared light curve, constrain dust property • Directly comparable to evolution of

asteroids in the solar system • Sublimation? • Collisions? • Rotational instability? • Tidal force?

Hubble: Active Asteroid

Take Home Message

#1. JWST will return the mineral compositions of extrasolar minor planets #2. JWST will constrain the properties of transiting asteroids around white dwarfs

White Dwarf

H/He Atom Heavy Atom

About 25% WDs are polluted ~2000

10-3 AU

Roche Limit 1987

Infrared Excess

Dust Sublimation

a disintegrating asteroid 2015

Giant Planet

???

10 AU

Searches for Planets around White Dwarfs

• Direct Imaging: • 7MJ planet/brown dwarf(?) around

WD0806-661 at 2500AU (Luhman et al. 2011)

• 6 WDs with HST/NICMOS, > 6MJ@12AU (Debes et al. 2005)

• 29 WDs with Gemini/NIRI & VLT/ISAAC, >8MJ@35AU (DODO Survey, Hogan et al. 2011)

• JWST: NIRCAM, ~2MJ@10AU

• Planetary Transits: • 1900 WDs in Pan-STARR1, <0.5% Jupiter-sized

planets with periods <0.2 d (Fulton et al. 2014)

JWST: Detecting Bio-Markers in Habitable Zone Earth Transiting White Dwarfs

Loeb & Maoz 2013

Flux

Simulated JWST Transmission Spectra NIRISS spectra (~5hr)

•  WD Habitable Zone: 0.05-0.2 AU for 3 Gyr (Agol 2011)

•  Ideal for transit spectroscopy

Take Home Message

#1. JWST will return the mineral compositions of extrasolar minor planets #2. JWST will constrain the properties of transiting asteroids around white dwarfs #3. JWST is in a good position to detect and characterize planets around white dwarfs

Thank you!