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arXiv · 2511.23368

The Kinematic Properties of T\.ZO Candidate HV 11417 with Gaia DR3

Anna J. G. O'Grady
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Abstract

HV 11417 is a candidate Thorne-\.Zytkow Object, a red supergiant with a neutron star core, located within the Small Magellanic Cloud (SMC). Previous studies have questioned, using Gaia DR2 data, whether HV 11417 was truly located at the distance of the SMC or was instead a foreground star. However, the proper motion measurement uncertainties for HV 11417 in DR2 were high. In this work, we use Gaia DR3 data to show that HV 11417 is very likely to be a true member of the SMC. We further analyze the kinematics of HV 11417 relative to its local environment, and compare it to populations of massive and evolved stars in the SMC. We find HV 11417 has a local transverse velocity of $52\pm15$ km/s, and thus qualifies as a runaway star (v$_\mathrm{loc}\geq$ 30 km/s). This runaway classification does not conclusively prove its nature as a T\.ZO, particularly given results from recent T\.ZO models, but does indicate that HV 11417 experienced a kinematic disruption in its evolution.

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Anna J. G. O'Grady. 2025-11-28. The Kinematic Properties of T\.ZO Candidate HV 11417 with Gaia DR3. https://doi.org/10.33232/001c.155625

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