The initial-to-final mass relation of white dwarfs in intermediate-separation binaries

TL;DR

This study investigates how binary interactions influence the initial-to-final mass relation of white dwarfs in intermediate-separation systems, revealing deviations from single-star models and suggesting complex binary evolution effects.

Contribution

It provides the first detailed analysis of the initial-to-final mass relation for white dwarfs in intermediate-separation binaries, highlighting the impact of binary interactions on stellar evolution.

Findings

Identification of two distinct WD populations with different formation histories.

Evidence of deviations from the standard IFMR in binary systems.

Potential presence of hierarchical triples affecting WD formation.

Abstract

We examine the applicability of the initial-to-final mass relation (IFMR) for white dwarfs (WDs) in intermediate-separation binary systems (approximately 1 AU), using astrometric binaries identified in open clusters from Gaia DR3. A careful analysis of the astrometric orbits and spectral energy distributions isolates 33 main-sequence (MS) stars with highly likely WD companions. By combining cluster age estimates, dynamically measured WD masses, and, where available, WD cooling temperatures, we derive progenitor masses for 26 WD candidates. Our analysis suggests the presence of two distinct WD populations: (i) low-mass WDs, likely shaped by binary interactions during the progenitor's red-giant phase; and (ii) "spender" WDs, which experienced higher-than-expected mass loss and have progenitor masses above the IFMR predictions. The rest of the candidates, referred to as the "others", represent systems with inconclusive formation mechanisms. We suggest that at least some of these systems might be hierarchical triples, where the companion to the MS is a double WD or a double-WD merger product. However, follow-up studies are required to determine the nature of each case. These results highlight significant deviations from the IFMR derived for isolated WDs, emphasizing the role of binary evolution. Follow-up observations, particularly in the far-ultraviolet, are crucial for refining these findings and advancing our understanding of mass transfer processes and binary evolution pathways.