New white dwarfs for the stellar initial mass-final mass relation (…preliminary results!) Paul D Dobbie Australian Astronomical Observatory 16th August 2010 Martin Barstow, Matt Burleigh, Ralf Napiwotzki, Sarah Casewell, Kurtis Williams, Ivan Hubeny, Gilles Fontaine, David Boyce,Quentin Parker, Richard Baxter

The stellar initial mass final mass relation 16th August 2010 Predicted correlation between MS mass and remnant mass of low/intermediate mass star. Prescription for mass of metal enriched gas returned to ISM. Chemical evolution of galaxies (e.g. C,N, s-process elements) IFMR remains a challenge to calculate from first principles.

The stellar initial mass final mass relation 16th August 2010 Usually constrained using WD members of star clusters Associate WD mass and cooling time with stellar lifetime (e.g. numerous papers of Weidemann, Koester, Reimers in 70s/80s/90s). End of talk at last meeting drew together data from 11 open clusters with near solar metallicity + WD in Sirius system:

The stellar initial mass final mass relation 16th August 2010

What’s new ? 16th August 2010 Target rich (nearby) cluster(s) τ~ Myr to further study purported change in gradient of IFMR at M init ~ 4M  NGC2516: 4 known WD members (M>0.9M  ),  ~150Myr, M tot ~1000M  (MNRAS, 333, 547). NGC3532:  ~300Myr, M tot ~1200M  (A&AS, 104, 379), 4 known WD members……expect ~8  4 WDs (NGC2287:  ~240Myr, M tot ~720M  (A&A, 437, 483), 2 known WD members….expect ~6  3 WDs)

CCD surveys of NGC3532 and NGC th August 2010 Plan B → obtained imaging data from ESO archive. NGC3532, NGC2287 observed with 2.2m + WFI in B, V + I bands, down to B~V~21.5 although only 1 pointing per cluster. Approximate zeropoints / default extinction coefficients → ~10% photometry

CCD surveys of NGC3532 and NGC th August 2010

VLT spectroscopy: temperatures and gravities 16th August 2010 Two nights of VLT + FORS time earlier this year to obtain good S/N low resolution optical spectroscopy. Observed 3 objects in NGC2287 and 4 in NGC3532, poor weather first night prevented additional follow-up. Compared observed H-Balmer lines to synthetic profiles from TLUSTY + SYNSPEC in XSPEC → T eff and log g NB. These models use original Lemke profiles, not more recent and physically realistic Montreal calculations.

New imaging: robust photometry and distances 16th August 2010 Obtained new V band photometry with Magellan + IMACS. Absolute magnitudes using grids of synthetic photometry (Montreal group) and spectroscopic temperatures and surface gravities.

…and proper motions 16th August 2010

Preliminary thoughts in context of the IFMR 16th August 2010 WDJ potentially heaviest cluster WD to date, M~1.12  0.04M  (CO models) or 1.08M  (ONe models). On ‘classical’ CO core ignition limit (~1.1M  ) and above more recent estimates (~1.05M  ). Likely to be of ONe core composition (ie. an ultra-massive WD).  cool (~ Myr) consistent with SF from large intermediate mass star (M≥4.5M  ). Further observational evidence that SSE can produce UMWD (at solar metalicity).

Preliminary thoughts in the context of the IFMR 16th August 2010 New NGC3532 WDs fainter but not substantially more massive (M~ M  ) than previously known WD-10 (M~0.97M  ). Formation of 4 WDs with M>0.9M  spans ~100Myr for little change in their mass so consistent with flatter IFMR at M init >4M  Performed 2 fits  1) simple line and 2) model allowing gradient M init ~4M . Latter provides improved description - mildly significant. Conclusion not very sensitive to age of cluster between plausible limits.

The white dwarf mass distribution. 16th August 2010 New NGC3532 WDs lend further support to earlier suggestion that O/C WD data  IFMR less steep at M init >4M  than immediately below. Adds to evidence that no need to invoke more complex channel to produce bulk of WDs with M~ M  Results maybe bolstered with spectral follow-up of 3 remaining candidate WD members and more spatially extensive CCD search / spectral follow-up of cluster.

Summary 16th August 2010 Performed preliminary CCD search of NGC2287 and NGC3532 for fainter WD members and unearthed four new massive cluster WDs. Revealed potentially most massive cluster WD to date and further evidence that single star evolution can produce ultra- massive WDs. New NGC3532 WDs lend support to our earlier suggestion that we are seeing change in slope of IFMR at M init ~4M  as predicted by theory.