The White Dwarf Initial-Final Mass Relation for Progenitor Stars From 0.85 to 7.5 M$_\odot$

Abstract: We present the initial-final mass relation (IFMR) based on the self-consistent analysis of Sirius B and 79 white dwarfs from 13 star clusters. We have also acquired additional signal on eight white dwarfs previously analyzed in the NGC 2099 cluster field, four of which are consistent with membership. These reobserved white dwarfs have masses ranging from 0.72 to 0.97 M$\odot$, with initial masses from 3.0 to 3.65 M$\odot$, where the IFMR has an important change in slope that these new data help to observationally confirm. In total, this directly measured IFMR has small scatter ($\sigma$ = 0.06 M$\odot$) and spans from progenitors of 0.85 to 7.5 M$\odot$. Applying two different stellar evolutionary models to infer two different sets of white dwarf progenitor masses shows that when the same model is also used to derive the cluster ages, the resulting IFMR has weak sensitivity to the adopted model at all but the highest initial masses ($>$5.5 M$\odot$). The non-linearity of the IFMR is also clearly observed with moderate slopes at lower masses (0.08 M${\rm final}$/M${\rm initial}$) and higher masses (0.11 M${\rm final}$/M${\rm initial}$) that are broken up by a steep slope (0.19 M${\rm final}$/M${\rm initial}$) between progenitors from 2.85 to 3.6 M$\odot$. This IFMR shows total stellar mass loss ranges from 33\% of M${\rm initial}$ at 0.83 M$\odot$ to 83\% of M${\rm initial}$ at 7.5 M$\odot$. Testing this total mass loss for dependence on progenitor metallicity, however, finds no detectable sensitivity across the moderate range of -0.15 $<$ [Fe/H] $<$ +0.15.

Overview of "The White Dwarf Initial-Final Mass Relation for Progenitor Stars From 0.85 to 7.5 M$_\odot$"

The paper "The White Dwarf Initial-Final Mass Relation for Progenitor Stars From 0.85 to 7.5 M$_\odot$" by Cummings et al. investigates the initial-final mass relation (IFMR) of white dwarfs using observational data from multiple star clusters and theoretical models. The IFMR is essential for understanding stellar evolution, particularly in the later stages where a star sheds its outer layers and subsequently forms a white dwarf, revealing its core mass.

Methodology and Data Collection

The authors analyze Sirius B and 79 white dwarfs from 13 star clusters, incorporating additional signals from eight white dwarfs within NGC 2099 to refine the understanding of the IFMR, particularly in the range of initial masses from 3.0 to 3.65 M$_\odot$. Spectroscopic analysis is utilized to determine white dwarf masses and cooling ages, and stellar evolutionary models are applied to infer progenitor masses and cluster ages.

The study employs two sets of stellar evolutionary models: PARSEC and MIST isochrones, allowing for a comparison of inferred progenitor masses under different theoretical assumptions. The paper presents a detailed analysis and re-evaluation of white dwarfs previously analyzed, utilizing updated methods and observational techniques to ensure consistency across datasets.

Findings and Implications

The IFMR obtained in this study demonstrates low scatter (σ = 0.06 M$\odot$) and spans progenitor masses from 0.85 to 7.5 M$\odot$. Key features include moderate slopes at lower (0.08 M${\rm final}$/M${\rm initial}$) and higher masses (0.11 M${\rm final}$/M${\rm initial}$), separated by a steep slope (0.19 M${\rm final}$/M${\rm initial}$) between progenitors of 2.85 to 3.6 M$_\odot$. This nonlinear behavior confirms previous observations, marking a significant change in the slope of the IFMR.

Total stellar mass loss is calculated, ranging from 33% at 0.83 M$\odot$ to 83% at 7.5 M$\odot$. The analysis finds no detectable sensitivity of this total mass loss to progenitor metallicity within the modest range examined (–0.15 < [Fe/H] < +0.15), indicating that other factors may drive mass loss variations.

Comparisons with Theoretical Models

The study compares empirical IFMR data with theoretical predictions, noting remarkable consistency in intermediate mass ranges (3 to 4 M$\odot$). However, a systematic offset of about 0.1 M$\odot$ exists, suggesting that current models may not perfectly predict final white dwarf masses for high-mass progenitors. These offsets underscore potential gaps in our understanding of mass loss rates and stellar evolution processes like TP-AGB and third dredge-up.

Future Prospects

The paper emphasizes the need for further observations, especially in mass ranges where data is sparse, to refine the IFMR and improve theoretical models' predictive power. Observations of white dwarfs from clusters with more extreme metallicity values could provide valuable insight into the metallicity dependence of stellar mass loss.

In conclusion, Cummings et al.'s research provides a robust framework for understanding the relation between the initial and final masses of stars, offering significant insights into stellar evolution and mass loss mechanisms. This work serves as an anchor for future exploration into the complex processes governing the lifecycle of stars.