Central stars? Do bipolar PNe really have more massive progenitors? Central stars? Eva Villaver (STScI/ESA) X

Outline Central star masses MageLlanic Clouds RESULTS in the Galaxy Hints from the progenitors: Galactic Scale Height CHemical Enrichment Possibilities?

HOW DO we determine masses? M CS /M  =0.5+(1.8 x10 -5 ) L/L 

How we weigh the stars in the LMC and SMC + Combined with Ground-based data (c,HeII 4686Å fluxes): Jacoby & Kaler (1993); Meatheringham et al. (1988); Meatheringham & Dopita (1991); Vassiliadis et al. (1992); Boronson & Liebert (1989); Monk et al. (1988); Leisy & Dennefeld (1996); Dopita & Meatheringham (1991ab); Shaw et al (2004); Palen et al. (2004). HST data: STIS broadband imaging and WFPC2 (Stromgren y) (Shaw et al. 2001,2007 Stanghellini et al. 2002, 2003)

Results in the LMC: (7) = 0.63± 0.06 R (19) = 0.65± 0.09 E (9) = 0.64± 0.04 B From: Villaver, Stanghellini & Shaw (2003) Villaver, Stanghellini & Shaw (2007)

Results in the Galaxy = 0.62± 0.08 R = 0.62 ± 0.07 E = 0.60± 0.03 B Derived from the Stanghellini et al. (2002) sample to an extinction limit of c < 1 Manchado et al. (2000)

No strong empirical evidence CEntral stars of Bipolar PNe Are more massive BIASES : Method? 4 B, 30 E, 10 R spectroscopy Small number statistics YES always Fainter faster? Yes if more massive....no evidence From detection vr non-detection RATE in the LMC Hotter central stars? No evidence in Stanghellini et al. (2002) or in the LMC

Galactic SCALE Height Corradi & Schwarz (1995) (400 PNe) =130 pc BIPOLAR =320 pc ELLIPTICALS Manchado, Villaver, Stanghellini & Guerrero (2000) (255 PNe) = 179 pc BIPOLARS = 308 pc ELIPTICALS = 753 pc ROUND

Galactic Kinematics of Bipolars Bipolar PNe from a young disk population Zuckermann & Gatley (1988), Corradi & Schwarz (1995). consistent with a M MS ~3 M 

Chemical Enrichment N/O and He abundances are that of the type I PNe defined by Peimbert and Torres-Peimbert (1987). He/H ≥ and log(N/O) > − 0.3. From Corradi & Schwarz (1995) = 2.37 ELLIPTICALS = 4.37 BIPOLARS From Stanghellini, Villaver, Manchado & Guerrero (2002) = 1.71 ROUND = 1.51 ELLIPTICALS = 5.66 BIPOLARS See also Kwitter and Henry (2001) Perinotto et al. (2004)

Hints from the chemistry M  Only isotopic ratios modified Convection DURING the AGB M  C and He abundances are increased 3 rd dredge-up FORMATION OF C-STARS 3-8 M  HBB N and He increase Long period O- STARS Herwig 00, Karakas 02, Pols 01, Strainero 97, Stancliffe 04

Other hints Bipolar & massive progenitors Garcia-Hernandez et al. (2007) have identified a sample of obscure massive O-rich stars in the Galaxy through the analysis of Li and Zr abundances HBB, higher N. Stanghellini et al. (2007) Spitzer spectra of PNe in the LMC and SMC. C/O 1 is asymmetric. Undermassive white dwarfs (0.47 M  ) in a high metallicity cluster (Kalirai et al. 2007).

How well do we know the initial-to-final mass relation? Weidemann (2000) monotonic IFMR. +Claver et al. (01) & Williams et al. (04) large scatter in the IFMR: A MS 3-4 M  ends up anywhere between 0.65 and 0.8 M  Kalirai et al. (2005) added 12 WDs from NGC From Kalirai et al. (2005)

SO.....? MASS-LOSS HIGHER ???? O-stars ~O.6 M  M MS > 4 M  C-stars

Can Mass-Loss be a problem? Dust-driven winds work well for C stars but run into problems to explain mass-loss for O-stars. (Woitke 2006 Hofner & Andersen 07)

Summary: NO strong empirical evidence of bipolar PNe to have more massive central stars (Villaver et al. 2003, 2007). STRONG empirical evidence that bipolar have more massive progenitors. Massive progenitors loose more mass HOW? Common envelope? Undermassive WDs Mass-loss rates enhanced for the massive O-rich stars? We need further constrains for the IFMR.