New white dwarfs for the stellar initial mass-final mass relation (

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New white dwarfs for the stellar initial
mass-final mass relation (preliminary results!)

• Paul D Dobbie
• Australian Astronomical Observatory

Martin Barstow, Matt Burleigh, Ralf Napiwotzki,
Sarah Casewell, Kurtis Williams, Ivan Hubeny,
Gilles Fontaine, David Boyce,Quentin Parker,
Richard Baxter
16th August 2010
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The stellar initial mass final mass relation

• 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.

16th August 2010
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The stellar initial mass final mass relation

• 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

16th August 2010
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The stellar initial mass final mass relation
16th August 2010
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Whats new ?

• Target rich (nearby) cluster(s) t250-300Myr to
  further study purported change in gradient of
  IFMR at Minit 4M?
• NGC2516 4 known WD members (Mgt0.9M?), ?150Myr,
  Mtot1000M? (MNRAS, 333, 547).
• NGC3532 ?300Myr, Mtot1200M? (AAS, 104, 379),
  4 known WD membersexpect 8?4 WDs
• (NGC2287 ?240Myr, Mtot720M? (AA, 437, 483), 2
  known WD members.expect 6?3 WDs)

16th August 2010
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CCD surveys of NGC3532 and NGC2287

• Plan B ? obtained imaging data from ESO archive.
• NGC3532, NGC2287 observed with 2.2m WFI in B, V
  I bands, down to BV21.5 although only 1
  pointing per cluster.
• Approximate zeropoints / default extinction
  coefficients ? 10 photometry

16th August 2010
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CCD surveys of NGC3532 and NGC2287

16th August 2010
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VLT spectroscopy temperatures and gravities

• 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 ? Teff
  and log g
• NB. These models use original Lemke profiles, not
  more recent and physically realistic Montreal
  calculations.

16th August 2010
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New imaging robust photometry and distances

• Obtained new V band photometry with Magellan
  IMACS.
• Absolute magnitudes using grids of synthetic
  photometry (Montreal group) and spectroscopic
  temperatures and surface gravities.

16th August 2010
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and proper motions
16th August 2010
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Preliminary thoughts in context of the IFMR

• WDJ0646-203 potentially heaviest cluster WD to
  date, M1.12?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 (150-200Myr) consistent with SF from large
  intermediate mass star (M4.5M?). Further
  observational evidence that SSE can produce UMWD
  (at solar metalicity).

16th August 2010
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Preliminary thoughts in the context of the IFMR

• New NGC3532 WDs fainter but not substantially
  more massive (M0.9-1.0M?) than previously known
  WD-10 (M0.97M?).
• Formation of 4 WDs with Mgt0.9M? spans 100Myr for
  little change in their mass so consistent with
  flatter IFMR at Minitgt4M?
• Performed 2 fits ? 1) simple line and 2) model
  allowing gradient change _at_ Minit4M?. Latter
  provides improved description - mildly
  significant. Conclusion not very sensitive to age
  of cluster between plausible limits.

16th August 2010
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The white dwarf mass distribution.

• New NGC3532 WDs lend further support to earlier
  suggestion that O/C WD data ? IFMR less steep at
  Minitgt4M? than immediately below.
• Adds to evidence that no need to invoke more
  complex channel to produce bulk of WDs with
  M0.8-1.0M?
• Results maybe bolstered with spectral follow-up
  of 3 remaining candidate WD members and more
  spatially extensive CCD search / spectral
  follow-up of cluster.

16th August 2010
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Summary

• 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 Minit4M? as predicted by theory.

16th August 2010