نجم مزدوج داخل نجم مزدوج سريع

الملخص الأصلي

كما كتبه المؤلفون، بالإنجليزية arXiv:2603.09489

We present the first on-sky demonstration of dual-field interferometry at the CHARA Array and the first direct resolution of the inner Ba--Bb subsystem in the bright hierarchical triple $$\alpha$$ Piscium. Using $$H$$-band fringe tracking on component A with MIRC-X to stabilize $$K$$-band science fringes on component B with MYSTIC, we detected a companion at a projected separation of 7 mas, confirming a long-suspected but previously unresolved short-period subsystem within the B component. The nearly equal $$H/K$$-band flux ratio indicates that Ba and Bb are near-twin F-type stars, consistent with the two narrow-lined components seen in optical spectra of B. By combining CHARA interferometry with archival VLTI/GRAVITY astrometry and radial velocities from archival and new spectroscopy (NARVAL and ARCES), we derive a well-constrained orbit with a period of $$P = 25$$ d, eccentricity $$e \simeq 0.6$$, and inclination $$i \simeq 65^\circ$$, yielding precise dynamical masses of $$1.668\pm0.033\,M_\odot$$ and $$1.646\pm0.029\,M_\odot$$. No additional companion is detected down to $$\Delta H \approx 5$$ at separations of 0.2--2 AU. We also obtained dual-field differential astrometry of the wide A--B pair with a precision of ~0.234 mas at a separation of $$1.85''$$, with an error budget dominated by internal delay-line actuators, fringe-tracking performance and chromatic dispersion. While the long-period outer orbit is not refined by these measurements, their agreement with the published astrometric orbit provides an on-sky validation of the CHARA dual-field mode. These results establish $$\alpha$$ Psc as a well-characterized hierarchical system suitable for future benchmark studies and demonstrate CHARA's new capability for off-axis interferometry and sub-mas astrometry on arcsecond-scale binaries.