Spectroscopic Analysis of the mid-IR excesses of WDs
Jana Bilikova1
You-Hua Chu1, Kate Su2, Robert Gruendl1, et al.1U. of Illinois at Urbana-Champaign, 2U. of Arizona
Spitzer MIPS 24 μm Survey of Hot WDs
WD Name PN Teff (kK) F24(mJy)
LIR/L*
K1-22 K1-22 141 1.07 3.1 E-5NGC 2438 NGC 2438 114 12.4 4.5 E-4WD 0103+732 EGB 1 150 2.76 1.3 E-5WD 0109+111 110 0.27 4.9 E-6WD 0127+581 Sh2-188 102 0.34 2.7 E-5WD 0439+466 Sh2-216 95 0.98 3.7 E-6WD 0726+133 Abell 21 130 0.92 1.6 E-5WD 0950+139 EGB 6 110 11.7 2.6 E-4WD 1342+443 79 0.22 4.0 E-5
WD 2226-210 Helix 110 48.0 2.5 E-4
Spitzer Archival search
• Serch for CSPNs with IR excess• 60 PNe examined • 18 photometry carried out• 6 show IR excess: NGC 6804, NGC 7139 NGC 2438, NGC 2346, NGC 6853, NGC 6905
Mid-IR emission of hot WDs
Possible Origins of IR Excesses
• Collisions of KBOs• Binary evolution• Compact nebulosity in born-again PNe
KPNO Echelle Spectra
[OIII]
Hα
Abell 30
NGC 2438 EGB 6
EGB 1
• H-poor: feature in [OIII] does not show up in Hα • All [OIII] features show Hα counterparts• Can eliminate the compact H-poor nebulosity scenario
Our dust disk model
• Optically thin• Dust grains
- silicates/amorphous carbon- sizes: n(a) ~ a-3.5
- amin set by β=Frad/Fg of 0.5 (Artymowicz & Clampin 1997)
- Qabs from Mie theory• Uniform surface density
WD 0439+466
• The closest CSPN Sh2-216• D=129 pc (Harris et al. 2007)
8
40’’
5’
Sh 2-216 model
Teff = 95,000 Klog g = 6.9M = 0.55 M
L = 160 L (Rauch et al. 2007)
amin ~ 40-80 umR ~ 60-100 AUM = 0.001 Mearth
CSPN K1-22
40’’
2’’
• HST has resolved a companion at 0.35’’ (~450 AU) from the CSPN (Ciardullo 1999).
• D = 1.33 kpc (Ciardullo 1999)
CSPN K1-22 model
Teff = 141,000 Klog g = 6.73M = 0.59 M
(Rauch et al. 1999)
L = 325 L (phot)
Kurucz model atm.Teff = 5,000 KM0V star amin ~ 250 um
R ~ sublim - 40 AUM = 0.002 Mearth
[O IV]
[Ne III]
WD 0103+732
Distance = 650 pc (Napiwotzki 2001)
WD 0103+732 model
Teff = 147,000 Klog g = 7.34M = 0.65 M
(Napiwotzki 2001)
L = 480 L (phot)
amin ~ 340 umR ~ 200 - 360 AUM = 0.14 Mearth
Beware!• Detailed spectral shape of the WD matters
- model atmospheres have more UV emission hotter grains disk properties- e.g. WD 0103+732: ~480 Lsun, Rin ~ 200 AU
~1000 Lsun, Rin ~ 500 AU• Distance matters
- dist+phot LWD amin disk properties
- e.g. K1-22: d=1.33 kpc, L~300 Lsun d=3.4 kpc, L~1000 Lsun
• More complicatons
WD 0950+139 (EGB 6)
•Compact emission line source coincident withthe CSPN (Fleming, Liebert, Green 1986) •JHK excess (Fulbright & Liebert 1993)•HST: A companion 0.18 ‘’ away (Bond 1994)
•IRAC, MIPS excess•Featureless spectrum Su et al., in prep.
KPNO echelle
CSPN NGC 6804
Spitzer MIPS 24 um
• Central emission line source• Dust continuum, rising from J band• We also see a silicate feature at 10 um.
Gemini NIRI+Michelle
ORIGINS
• KBO collisions– Inner and outer edge (~100 AU)– Small dust mass (~0.1 Mearth)– Not too far for collisions (Dong et al.,Bonsor & Wyatt)
• Post-AGB binaries– Some CSPNs are binaries (maybe others hide a
companion?)– CSPN stage right after post-AGB (do post-AGB
binaries evolve into PNe?)
Conclusions• Near and mid-IR excess is a good indicator of
interesting phenomena• Great variety among IR excesses– Near-IR excess only, mid-IR excess only, both– No emission lines, only emission lines, both– Featureless dust continuum, mineralogical features– Known companions, no companions
• Each needs to be studied in detail individually• Stellar atmospheric models• Stay tuned!
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