Initial Mass-final Mass Relation Research Articles

Component masses of young, wide, non-magnetic white dwarf binaries in the Sloan Digital Sky Survey Data Release 7

We present a spectroscopic component analysis of 18 candidate young, wide, non-magnetic, double-degenerate binaries identified from a search of the Sloan Digital Sky Survey Data Release 7 (DR7). All but two pairings are likely to be physical systems. We show SDSS J084952.47+471247.7 + SDSS J084952.87+471249.4 to be a wide DA+DB binary, only the second identified to date. Combining our measurements for the components of 16 new binaries with results for three similar, previously known systems within the DR7, we have constructed a mass distribution for the largest sample to date (38) of white dwarfs in young, wide, non-magnetic, double-degenerate pairings. This is broadly similar in form to that of the isolated field population with a substantial peak around M~0.6 Msun. We identify an excess of ultra-massive white dwarfs and attribute this to the primordial separation distribution of their progenitor systems peaking at relatively larger values and the greater expansion of their binary orbits during the final stages of stellar evolution. We exploit this mass distribution to probe the origins of unusual types of degenerates, confirming a mild preference for the progenitor systems of high-field-magnetic white dwarfs, at least within these binaries, to be associated with early-type stars. Additionally, we consider the 19 systems in the context of the stellar initial mass-final mass relation. None appear to be strongly discordant with current understanding of this relationship.

Further investigation of white dwarfs in the open clusters NGC 2287 and NGC 3532

We report the results of a CCD imaging survey, complimented by astrometric and spectroscopic follow-up studies, that aims to probe the fate of heavy-weight intermediate mass stars by unearthing new, faint, white dwarf members of the rich, nearby, intermediate age open clusters NGC3532 and NGC2287. We identify a total of four white dwarfs with distances, proper motions and cooling times which can be reconciled with membership of these populations. We find that WDJ0643-203 in NGC2287, with an estimated mass of M=1.02-1.16Msun, is potentially the most massive white dwarf so far identified within an open cluster. Guided by the predictions of modern theoretical models of the late-stage evolution of heavy-weight intermediate mass stars, we conclude that there is a distinct possibility it has a core composed of O and Ne. We also determine that despite the cooling times of the three new white dwarfs in NGC3532 and the previously known degenerate member NGC3532-10 spanning ~90Myr, they all have remarkably similar masses (M~0.9-1Msun). This is fully consistent with the results from our prior work on a heterogeneous sample of ~50 white dwarfs from 12 stellar populations, on the basis of which we argued that the stellar initial mass-final mass relation is less steep at Minit>4Msun than in the adjacent lower initial mass regime. This change in the gradient of the relation could account for the secondary peak observed in the mass distribution of the field white dwarf population and mitigate the need to invoke close binary evolution to explain its existence. Spectroscopic investigation of numerous additional candidate white dwarf members of NGC3532 unearthed by a recent independent study would be useful to confirm (or otherwise) these conclusions.

A new detailed examination of white dwarfs in NGC 3532 and NGC 2287

We present the results of a photometric and spectroscopic study of the white dwarf candidate members of the intermediate age open clusters NGC 3532 and NGC 2287. Of the nine objects investigated, it is determined that six are probable members of the clusters, four in NGC 3532 and two in NGC 2287. For these six white dwarfs, we use our estimates of their cooling times together with the cluster ages to constrain the lifetimes and masses of their progenitor stars. We examine the location of these objects in initial mass–final mass space and find that they now provide no evidence for substantial scatter in initial mass–final mass relation (IFMR) as suggested by previous investigations. Instead, we demonstrate that, when combined with current data from other solar metallicity open clusters and the Sirius binary system, they hint at an IFMR that is steeper in the initial mass range 3 M⊙ ≲ M init ≲ 4 M⊙ than at progenitor masses immediately lower and higher than this. This form is generally consistent with the predictions of stellar evolutionary models and can aid population synthesis models in reproducing the relatively sharp drop observed at the high mass end of the main peak in the mass distribution of white dwarfs.

A massive white dwarf member of the Coma Berenices open cluster

We report the identification, from a photometric, astrometric and spectroscopic study, of a massive white dwarf member of the nearby, approximately solar metalicity, Coma Berenices open star cluster (Melotte 111). We find the optical to near-IR energy distribution of WD1216+260 to be entirely consistent with that of an isolated DA and determine the effective temperature and surface gravity of this object to be $T_{\rm eff}$=$15739^{+197}_{-196}$K and log $g$=$8.46^{+0.03}_{-0.02}$. We set tight limits on the mass of a putative cool companion, M$\simgreat$0.036M$_{\odot}$ (spatially unresolved) and M$\simgreat$0.034M$_{\odot}$, (spatially resolved and a$\simless$2500AU). Based on the predictions of CO core, thick-H layer evolutionary models we determine the mass and cooling time of WD1216+260 to be M$_{\rm WD}$=$0.90 \pm0.04$M$_{\odot}$ and $\tau$$_{\rm cool}$=$363^{+46}_{-41}$Myrs respectively. For an adopted cluster age of $\tau$=500$\pm$100Myrs we infer the mass of its progenitor star to be M$_{\rm init}$=$4.77^{+5.37}_{-0.97}$M$_{\odot}$. We briefly discuss this result in the context of the form of the stellar initial mass-final mass relation.

High-resolution optical spectroscopy of Praesepe white dwarfs

We present the results of a high-resolution optical spectroscopic study of nine white dwarf candidate members of Praesepe undertaken with the VLT and Ultraviolet and Visual Echelle Spectrograph. We find, contrary to a number of previous studies, that WD0836+201 (LB390, EG59) and WD0837+199 (LB393, EG61) are magnetic and non-magnetic white dwarfs, respectively. Subsequently, we determine the radial velocities for the eight non-magnetic degenerates and provide compelling evidence that WD0837+185 is a radial velocity variable and possibly a double-degenerate system. We also find that our result for WD0837+218, in conjunction with its projected spatial location and position in initial mass–final mass space, argues it is more likely to be a field star than a cluster member. After eliminating these two white dwarfs, and WD0836+199 which has no clean Sloan Digital Sky Survey photometry, we use the remaining five stars to substantiate modern theoretical mass–radius relations for white dwarfs. In light of our new results, we re-examine the white dwarf members of Praesepe and use them to further constrain the initial mass–final mass relation (IFMR). We find a near-monotonic IFMR, which can still be adequately represented by simple linear function with only one outlier which may have formed from a blue straggler star.

New Praesepe white dwarfs and the initial mass–final mass relation

We report the spectroscopic confirmation of four further white dwarf members of Praesepe. This brings the total number of confirmed white dwarf members to eleven making this the second largest collection of these objects in an open cluster identified to date. This number is consistent with the high mass end of the initial mass function of Praesepe being Salpeter in form. Furthermore, it suggests that the bulk of Praesepe white dwarfs did not gain a substantial recoil kick velocity from possible asymmetries in their loss of mass during the asymptotic giant branch phase of evolution. By comparing our estimates of the effective temperatures and the surface gravities of WD0833+194, WD0840+190, WD0840+205 and WD0843+184 to modern theoretical evolutionary tracks we have derived their masses to be in the range 0.72-0.76Msun and their cooling ages \~300Myrs. For an assumed cluster age of 625+/-50Myrs the infered progenitor masses are between 3.3-3.5Msun. Examining these new data in the context of the initial mass-final mass relation we find that it can be adequately represented by a linear function (a0=0.289+/-0.051, a1=0.133+/-0.015) over the initial mass range 2.7Msun to 6Msun. Assuming an extrapolation of this relation to larger initial masses is valid and adopting a maximum white dwarf mass of 1.3Msun, our results support a minimum mass for core-collapse supernovae progenitors in the range ~6.8-8.6Msun.

Synthetic Post–Asymptotic Giant Branch Evolution: Basic Models and Applications to Disk Populations

We explore the realm of post-Asymptotic Giant Branch (post-AGB) stars from a theoretical viewpoint, by constructing synthetic population of transition objects, proto-Planetary Nebulae, Planetary Nebulae Nuclei, and post-Planetary Nebulae objects. We use the Montecarlo procedure to filter out the populations accordingly to a given set of assumptions. We explore the parameter space by studying the effects of the Initial Mass Function (IMF), the Initial Mass-Final Mass Relation (IMFMR), the transition time (t_tr), the envelope mass at the end of the envelope ejection (Me_r), the planetary nebula lifetime t_PN, the hydrogen- and helium-burning phases of the central stars. The results are discussed on the basis of the HR diagram distributions, on the Mv-t plane, and with mass histograms. We found that: (1) the dependence of the synthetic populations on the assumed IMF and IMFMR is generally mild; (2) the Me_r indetermination produces very high indeterminations on the t_tr and thus on the resulting post-AGB populations; (3) the synthetic models give a test check for the ratio of He- to H-burning PNNi. In this paper, disk post-AGB populations are considered. Future applications will include Magellanic Clouds PNe, and populations of bulges and elliptical galaxies.

Evolutionary Tests of the Planetary Nebula Luminosity Function

view Abstract Citations (14) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evolutionary Tests of the Planetary Nebula Luminosity Function Stanghellini, Letizia Abstract The planetary nebula luminosity function (PNLF) depends on the physical characteristics and evolutionary paths of the components. Changes in the nebular and stellar parameters may influence the extragalactic distance scale based on the PNLF. We aim at studying from a theoretical viewpoint how changes in the physical conditions of the parent galaxy and the evolutionary paths of the central stars and nebulae propagate into the PNLF. By means of synthesis of post-asymptotic giant branch evolution, we have tested the invariance of the distance scale based on the Hβ PNLF for changes in the evolutionary timescales, in the initial mass-final mass relation, and in the number of optically thick planetary nebulae (PNs) populating the PNLF. We start with a theoretical Hβ PNLF truncated at M∫ < 0.7 Msun, which we successfully check against its empirical homologue for SMC and LMC PNs. We obtain that small shifts in the transition time evolve into Hβ magnitude shifts of the high-luminosity cutoff up to 0.75 mag for constant star formation rate populations only, while intermediate/old populations are almost invariant with respect to these evolutionary time differences. We also obtain that a different initial mass-final mass relation does propagate into shifts in the Hβ PNLF, the effects being important only for young stellar populations. Finally, the high-luminosity cutoff of the Hβ PNLF seems to be invariant to the number of PNs considered. Overall, our results indicate that extreme care should be taken when using Hβ PNLF in the context of high-mass-high-luminosity PNs. Publication: The Astrophysical Journal Pub Date: October 1995 DOI: 10.1086/176325 Bibcode: 1995ApJ...452..515S Keywords: COSMOLOGY: DISTANCE SCALE; GALAXIES: STELLAR CONTENT; ISM: PLANETARY NEBULAE: GENERAL; STARS: EVOLUTION full text sources ADS | data products SIMBAD (2)

Temperatures, gravities, and masses for a sample of bright DA white dwarfs and the initial-to-final mass relation

The atmospheric parameters, T<SUB>eff</SUB> and log g, have been determined for a sample of 52 hydrogen-line (DA) white dwarfs by fitting optical spectra to theoretical model atmospheres. Multiple observations of each star allow an estimation of the accuracy of the method: the average external errors are 490 K in T<SUB>eff</SUB> and 0.06 in log g. Masses have been derived using white dwarf evolutionary models where finite temperature effects are taken into account. The average mass of the 46 DA stars in our sample with T<SUB>eff</SUB> greater than 12,000 K is 0.587 solar masses, with a dispersion of 0.166 solar masses while the mode of the distribution is between 0.50 and 0.55 solar masses. The mass distribution shows a low-mass (M less than 0.4 solar masses) tail of four objects which are most likely helium white dwarfs, the outcome of close binary evolution. Excluding those objects, the average mass becomes 0.609 solar masses, with a dispersion of 0.157 solar masses. When combining with the sample studied by Bergeron, Saffer, &amp; Liebert (1992), this leads to a set of 164 white dwarfs for which atmospheric parameters and masses have been obtained in a homogeneous way. In this sample 15 objects have M less than 0.4 solar masses, thus confirming that about 10% of catalog white dwarfs are helium white dwarfs produced in close binaries. The implications for the stellar initial mass-final mass relation are then discussed in some detail. Some individual objects of particular astrophysical interest are also briefly discussed.

Synthetic P-AGB Evolution

Extensive Montecarlo simulations of Post-Asymptotic Giant Branch (P-AGB) populations have been constructed, exploring the effects of various assumptions on synthetic H-R diagrams, luminosity functions, and inferred mass distributions. Such assumptions include the IMF, the initial mass-final mass relation, the AGB to PN transition time, the duration of the planetary nebula (PN) stage, etc. We have also investigated how the observational errors in luminosity and temperature propagate into the inferred mass distribution of the P-AGB stars.