March
2026
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2026AJ....171..137H
Authors
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Hughes, Joanne
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Kunder, Andrea
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Covey, Kevin
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Devine, Kathryn
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Larson, Kristen A.
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Campos, Carlos
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Price-Whelan, Adrian M.
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McEwen, Joseph E.
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Perren, Gabriel I.
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Johnson, Christian I.
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Horton, Craig
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Smith, Luke
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Torset, Sarah
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Luna, Cynthia
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Kolmanovsky, Matthew
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Kovisto, Fiona
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Villarta, Leander
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Vuong, Vy
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Simion, Iulia T.
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Webster, Kyle
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Silva, Erika
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Pilachowski, Catherine A.
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Rich, R. Michael
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Kader, Justin A.
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Koch-Hansen, Andreas J.
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Joyce, Meridith
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McAdam, Sean
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Benda, Faith
Abstract
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We present spectroscopic evidence for tidal debris associated with the bulge globular cluster NGC 6569, based on medium-resolution (R ∼ 11,000) spectra of 303 stars obtained with the Anglo-Australian Telescope. Targets were selected using Blanco DECam Bulge Survey photometry with Gaia DR3 astrometry, and span ∼7' ─ 30' (i.e., 1─5 rt, where rt is the King-model tidal radius) from the cluster center. Theoretical modeling shows that the Jacobi radii can vary between 8' ─ 11' and 18' ─ 22' over the orbit, likely leaving stars around the cluster that are transitioning into the predicted leading and lagging tidal tails. We identify 40 stars in this sample that exhibit chemical and kinematic properties consistent with previous, or borderline, cluster membership. The seven best candidates have S/N > 30, with [Fe/H] = ─0.83 ± 0.14 dex and [α/Fe] = +0.38 ± 0.06 dex, consistent with NGC 6569's bound population. Our findings provide evidence that NGC 6569 is actively losing stars through tidal stripping, contributing to the bulge field population at a present rate of 1.0─1.6 M⊙ Myr−1, which corresponds to ≍5.6% ± 1.3% of its present-day mass per Gyr. This work is part of the Milky Way Bulge Extra-Tidal Star Survey and represents our first detailed study of a massive bulge globular cluster in this context.
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