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Spectroscopic Analysis of the mid-IR excesses of WDs

Spectroscopic Analysis of the mid-IR excesses of WDs. Jana Bilikova 1 You- Hua Chu 1 , Kate Su 2 , Robert Gruendl 1, et al. 1 U. of Illinois at Urbana-Champaign, 2 U. of Arizona . Spitzer MIPS 24 μm Survey of Hot WDs WD Name PN T eff ( kK ) F 24 (mJy) L IR /L *

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Spectroscopic Analysis of the mid-IR excesses of WDs

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  1. 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

  2. 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-5 NGC 2438 NGC 2438 114 12.4 4.5 E-4 WD 0103+732 EGB 1 150 2.76 1.3 E-5 WD 0109+111 110 0.27 4.9 E-6 WD 0127+581 Sh2-188 102 0.34 2.7 E-5 WD 0439+466 Sh2-216 95 0.98 3.7 E-6 WD 0726+133 Abell 21 130 0.92 1.6 E-5 WD 0950+139 EGB 6 110 11.7 2.6 E-4 WD 1342+443 79 0.22 4.0 E-5 WD 2226-210 Helix 110 48.0 2.5 E-4

  3. Spitzer Archival search • Serchfor 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

  4. Mid-IR emission of hot WDs

  5. Possible Origins of IR Excesses • Collisions of KBOs • Binary evolution • Compact nebulosity in born-again PNe

  6. KPNO EchelleSpectra EGB 6 NGC 2438 EGB 1 Abell 30 [OIII] Hα • H-poor: feature in [OIII] does not show up in Hα • All [OIII] features show Hαcounterparts • Can eliminate the compact H-poor nebulosity scenario

  7. 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

  8. WD 0439+466 • The closest CSPN Sh2-216 • D=129 pc (Harris et al. 2007) 5’ 40’’

  9. Sh 2-216 model Teff = 95,000 K log g = 6.9 M = 0.55 M L = 160 L (Rauch et al. 2007) amin ~ 40-80 um R~ 60-100 AU M = 0.001 Mearth

  10. CSPN K1-22 2’’ 40’’ • HST has resolved a companion at 0.35’’ (~450 AU) from the CSPN (Ciardullo 1999). • D = 1.33 kpc (Ciardullo 1999)

  11. CSPN K1-22 model [O IV] [Ne III] Teff = 141,000 K log g = 6.73 M = 0.59 M (Rauch et al. 1999) L = 325 L (phot) Kurucz model atm. Teff = 5,000 K M0V star amin ~ 250 um R~sublim - 40 AU M = 0.002 Mearth

  12. WD 0103+732 Distance = 650 pc (Napiwotzki 2001)

  13. WD 0103+732 model Teff = 147,000 K log g = 7.34 M = 0.65 M (Napiwotzki 2001) L = 480 L (phot) amin ~ 340 um R~ 200 - 360 AU M = 0.14 Mearth

  14. 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

  15. WD 0950+139 (EGB 6) KPNO echelle • Compact emission line source coincident with • the 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.

  16. CSPN NGC 6804 Spitzer MIPS 24 um Gemini NIRI+Michelle • Central emission line source • Dust continuum, rising from J band • We also see a silicate feature at 10 um.

  17. 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?)

  18. 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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