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# Constraining mass transfer histories of blue straggler stars with COS spectroscopy of white dwarf companions

Gosnell, Natalie M., Leiner, Emily M., Mathieu, Robert D., Geller, Aaron M., Knigge, Christian, Sills, Alison, Leigh, Nathan W. C. and Cargile, Phillip (2019) Constraining mass transfer histories of blue straggler stars with COS spectroscopy of white dwarf companions. The Astrophysical Journal. (In Press)

Record type: Article

## Abstract

Recent studies show that the majority of blue straggler stars in old open clusters are formed through mass transfer from an evolved star onto a main sequence companion, resulting in a blue straggler and white dwarf in a binary system. We present constraints on the formation histories and mass transfer efficiencies for two blue straggler-white dwarf binaries in open cluster NGC 188 resulting from measuring white dwarf cooling temperatures and surface gravities with HST COS far-ultraviolet spectroscopy. We determine that one system, WOCS 4540, formed through Case C mass transfer resulting in a CO-core white dwarf with a temperature of $17200^{+100}_{-80}$ K and a $\log g$ of $7.76^{+0.03}_{-0.01}$. These fitted values correspond to a mass of $0.50^{+0.05}_{-0.01}$ $M_{\odot}$ and an age of $94^{+7}_{-3}$ Myr. The other system, WOCS 5379, formed through Case B mass transfer resulting in a He-core white dwarf with a temperature of $15400^{+280}_{-260}$ K and a $\log g$ of $7.45^{+0.06}_{-0.06}$, corresponding to a mass of $0.40^{+0.04}_{-0.04}$ $M_{\odot}$ and an age of $230^{+22}_{-23}$ Myr. We determine possible progenitor binary systems with a grid of accretion models using MESA, and investigate whether these systems would lead to stable or unstable mass transfer. WOCS 4540 likely resulted from stable mass transfer during periastron passage in an eccentric binary system, while WOCS 5379 challenges our current understanding of the expected regimes for stable mass transfer from red giant branch stars. Both systems are examples of the benefit of using a detailed analysis to fine-tune our physical understanding of binary evolutionary processes.

Text
1904.02280v1 - Accepted Manuscript

Accepted/In Press date: 4 April 2019
Additional Information: 17 pages, 12 figures, 1 table, submitted to Astrophysical Journal
Keywords: astro-ph.SR

## Identifiers

Local EPrints ID: 430335
URI: https://eprints.soton.ac.uk/id/eprint/430335
ISSN: 0004-637X
PURE UUID: 55a4f7c2-8cd3-4195-94ae-473fbc56e28c

## Catalogue record

Date deposited: 25 Apr 2019 16:30

## Contributors

Author: Natalie M. Gosnell
Author: Emily M. Leiner
Author: Robert D. Mathieu
Author: Aaron M. Geller
Author: Alison Sills
Author: Nathan W. C. Leigh
Author: Phillip Cargile