A census of massive eclipsing binaries in the Whirlpool Galaxy
Abstract
We present a census of massive eclipsing binary (EB) candidates in the Whirlpool Galaxy (M51), a face-on spiral galaxy at 7.5 Mpc with Z∼ Z⊙. Using 34 epochs of red-optical Hubble Space Telescope (HST) photometry and a single epoch of broadband UV-optical photometry, we identify 173 massive EB candidates (>5 M⊙) with orbital periods Porb=1-30 days. The sample traces young stellar populations across the spiral arms of M51. Joint light-curve and spectral energy distribution fits for 136 systems yield binaries spanning Teff=10,000-50,000 K, R=7-66 R⊙, and masses of $5−120~{\rm M_\odot}$. We use detailed injection-recovery simulations to quantify the survey's completeness and infer intrinsic properties of the massive binary population. At the population level, we infer a close-binary fraction of fclose=27.4±7.1% for 2≤ Porb/d<20 and 0.1≤ q≤1. Over the same period range, the intrinsic period distribution is consistent with being log-uniform, dN/dlog Porb∝ Porbπ with π=0.29±0.32. These demographics broadly match those of massive-star populations in the Milky Way, LMC, and SMC, with tentative evidence for a lower close-binary fraction at lower metallicity. Across the ∼0.2-1.1 Z⊙ range spanned by these galaxies, the overall similarities suggest that the formation of close massive binaries depends only weakly on metallicity. Our survey establishes EBs as a powerful tool for measuring massive-binary demographics beyond the Local Group and provides a rich panchromatic census of ∼100,000 luminous stars and variables in M51.
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BibTeX
@misc{shariat2026census,
title = {{A census of massive eclipsing binaries in the Whirlpool Galaxy}},
author = {Cheyanne Shariat and Kareem El-Badry and Maude Gull and Daniel R. Weisz and Charlie Conroy and Alessandro Savino},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.19268},
eprint = {2609.19268},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.19268},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A census of massive eclipsing binaries in the Whirlpool Galaxy
AU - Cheyanne Shariat
AU - Kareem El-Badry
AU - Maude Gull
AU - Daniel R. Weisz
AU - Charlie Conroy
AU - Alessandro Savino
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.19268
UR - https://arxiv.org/abs/2609.19268
AB - We present a census of massive eclipsing binary (EB) candidates in the Whirlpool Galaxy (M51), a face-on spiral galaxy at 7.5 Mpc with Z∼ Z_⊙. Using 34 epochs of red-optical Hubble Space Telescope (HST) photometry and a single epoch of broadband UV-optical photometry, we identify 173 massive EB candidates (>5 M_⊙) with orbital periods P_orb=1-30 days. The sample traces young stellar populations across the spiral arms of M51. Joint light-curve and spectral energy distribution fits for 136 systems yield binaries spanning T_eff=10,000-50,000 K, R=7-66 R_⊙, and masses of $5−120~{\rm M_\odot}$. We use detailed injection-recovery simulations to quantify the survey's completeness and infer intrinsic properties of the massive binary population. At the population level, we infer a close-binary fraction of f_close=27.4±7.1% for 2≤ P_orb/d<20 and 0.1≤ q≤1. Over the same period range, the intrinsic period distribution is consistent with being log-uniform, dN/dlog P_orb∝ P_orb^π with π=0.29±0.32. These demographics broadly match those of massive-star populations in the Milky Way, LMC, and SMC, with tentative evidence for a lower close-binary fraction at lower metallicity. Across the ∼0.2-1.1 Z_⊙ range spanned by these galaxies, the overall similarities suggest that the formation of close massive binaries depends only weakly on metallicity. Our survey establishes EBs as a powerful tool for measuring massive-binary demographics beyond the Local Group and provides a rich panchromatic census of ∼100,000 luminous stars and variables in M51.
ER -