VLBA detections in the Oph-S1 binary system near periastron confirmation of its orbital elements and mass

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Author(s):	Ordonez-Toro, Jazmin ; Dzib, Sergio A. ; Loinard, Laurent ; Ortiz-Leon, Gisela ; Kounkel, Marina A. ; Galli, Phillip A. B. ; Masque, Josep M. ; Dupuy, Trent J. ; Quiroga-Nunez, Luis H. ; Rodriguez, Luis F. Total Authors: 10
Document type:	Journal article
Source:	Monthly Notices of the Royal Astronomical Society; v. 538, n. 3, p. 5-pg., 2025-03-19.
Abstract
Oph-S1 is the most luminous and massive stellar member of the nearby Ophiuchus star-forming region. Previous Very Long Baseline Array (VLBA) observations have shown it to be an intermediate-mass binary system (similar to 5M(circle dot)) with an orbital period of about 21 months, but a paucity of radio detections of the secondary near periastron could potentially have affected the determination of its orbital parameters. Here, we present nine new VLBA observations of Oph-S1 focused on its periastron passage in early 2024. We detect the primary in all observations and the secondary at five epochs, including three within about a month of periastron passage. The updated orbit, determined by combining our new data with 35 previous observations, agrees well with previous calculations and yields masses of 4.115 +/- 0.039M(circle dot )and 0.814 +/- 0.006M(circle dot ) for the two stars in the system. (AU)

FAPESP's process:	20/12518-8 - Dynamics and evolution of Young Stellar Clusters (DYSC)
Grantee:	Phillip Andreas Brenner Galli
Support Opportunities:	Research Grants - Young Investigators Grants