Spectroscopic Analysis of the midIR 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 K 1 -22 NGC 2438 WD 0103+732 WD 0109+111 WD 0127+581 WD 0439+466 WD 0726+133 WD 0950+139 WD 1342+443 K 1 -22 NGC 2438 EGB 1 WD 2226 -210 Helix Sh 2 -188 Sh 2 -216 Abell 21 EGB 6 Teff (k. K) F 24(m. Jy) LIR/L* 141 114 150 110 102 95 130 110 79 1. 07 12. 4 2. 76 0. 27 0. 34 0. 98 0. 92 11. 7 0. 22 3. 1 E-5 4. 5 E-4 1. 3 E-5 4. 9 E-6 2. 7 E-5 3. 7 E-6 1. 6 E-5 2. 6 E-4 4. 0 E-5 110 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 Abell 30 NGC 2438 EGB 1 EGB 6 [OIII] Hα • 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 -a min set by β=Frad/Fg of 0. 5 (Artymowicz & Clampin 1997) - Qabs from Mie theory • Uniform surface density

WD 0439+466 • The closest CSPN Sh 2 -216 • D=129 pc (Harris et al. 2007) 5’ 40’’ 8

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

CSPN K 1 -22 2’’ 40’’ • HST has resolved a companion at 0. 35’’ (~450 AU) from the CSPN (Ciardullo 1999). • D = 1. 33 kpc (Ciardullo 1999)

CSPN K 1 -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 M 0 V star amin ~ 250 um R ~ sublim - 40 AU M = 0. 002 Mearth

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

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

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. K 1 -22: d=1. 33 kpc, L~300 Lsun d=3. 4 kpc, L~1000 Lsun • More complicatons

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.

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.

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!