The Initial-Final Mass Relation: Direct Constraints at the Low-Mass End

The initial-final mass relation represents a mapping between the mass of a white dwarf remnant and the mass that the hydrogen-burning main-sequence star that created it once had. The empirical relation thus far has been constrained using a sample of [image]40 stars in young open clusters, ranging in...

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Veröffentlicht in:The Astrophysical journal 2008-03, Vol.676 (1), p.594-609
Hauptverfasser: Kalirai, Jasonjot S, Hansen, Brad M. S, Kelson, Daniel D, Reitzel, David B, Rich, R. Michael, Richer, Harvey B
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Sprache:eng
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Zusammenfassung:The initial-final mass relation represents a mapping between the mass of a white dwarf remnant and the mass that the hydrogen-burning main-sequence star that created it once had. The empirical relation thus far has been constrained using a sample of [image]40 stars in young open clusters, ranging in initial mass from [image]2.75 to 7 [image], and shows a general trend that connects higher mass main-sequence stars with higher mass white dwarfs. In this paper, we present CFHT CFH12K photometric and Keck LRIS multiobject spectroscopic observations of a sample of 22 white dwarfs in two older open clusters, NGC 7789 ([image] Gyr) and NGC 6819 ([image] Gyr). We measure masses for the highest signal-to-noise ratio spectra by fitting the Balmer lines to atmosphere models and place the first direct constraints on the low- mass end of the initial-final mass relation. Our results indicate that the observed general trend at higher masses continues down to low masses, with [image] main-sequence stars forming [image] white dwarfs. When added to our new data from the very old cluster NGC 6791, the relation is extended down to [image] (corresponding to [image]). This extension of the relation represents a fourfold increase in the total number of hydrogen-burning stars for which the integrated mass loss can now be calculated from empirical data, assuming a Salpeter initial mass function. The new leverage at the low-mass end is used to derive a purely empirical initial-final mass relation. The sample of white dwarfs in these clusters also shows several interesting systems that we discuss further: a DB (helium) white dwarf, a magnetic white dwarf, a DAB (mixed hydrogen/helium atmosphere or a double degenerate DA+DB) white dwarf(s), and two possible equal-mass da double degenerate binary systems.
ISSN:0004-637X
1538-4357
DOI:10.1086/527028