Chandra/LETGS Studies of the Collisional Plasma in 4U 1626–67
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Hemphill_2021_ApJ_920_142.pdf
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Published version
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Author(s)
Hemphill, Paul B
Schulz, Norbert S
Marshall, Herman L
Chakrabarty, Deepto
Date Issued
2021
Journal
Astrophysical Journal
Publisher
American Astronomical Society
Citation
Hemphill, Paul B, Schulz, Norbert S, Marshall, Herman L and Chakrabarty, Deepto. 2021. "Chandra/LETGS Studies of the Collisional Plasma in 4U 1626–67." Astrophysical Journal, 920 (2).
Version
Final published version
Abstract
We present an analysis of \chandra/LETGS observations of the ultracompact
X-ray binary (UCXB) 4U 1626$-$67, continuing our project to analyze the
existing
Chandra gratings data of this interesting source. The extremely low mass,
hydrogen-depleted donor star provides a unique opportunity to study the
properties and structure of the metal-rich accreted plasma. There are strong,
double-peaked emission features of OVII-VIII and Ne IX-X, but no other
identified emission lines are detected. Our spectral fit simultaneously
models the emission line profiles and the plasma parameters, using a
two-temperature collisionally-ionized plasma. Based on our line profile
fitting, we constrain the inclination of the system to 25--60$^{\circ}$ and
the inner disk radius to $\sim$1500 gravitational radii, in turn constraining
the donor mass to $\lesssim$0.026 M_sun, while our plasma modeling confirms
previous reports of high neon abundance in the source, establishing a Ne/O
ratio in the system of $0.47 \pm 0.04$, while simultaneously estimating a
very low Fe/O ratio of $0.0042 \pm 0.0008$ and limiting the Mg/O ratio to
less than 1% by number. We discuss these results in light of previous work.
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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Persistent DSpace Link
DOI of Published Version
https://doi.org/10.3847/1538-4357/AC0ADE
