Dual-field interferometry uses a bright reference star for real-time fringe tracking, allowing a second beam combiner to record long coherent integrations on a fainter off-axis science target. At the Center for High Angular Resolution Astronomy (CHARA) Array, we implement this mode using the six-telescope MIRC-X and MYSTIC beam combiners in the H and K bands, respectively. We first demonstrated this capability in summer 2025 on the hierarchical triple $\alpha$~Piscium. MIRC-X tracked component A in the $H$ band, while MYSTIC observed component B in the K band, resolving the 7~mas Ba--Bb subsystem and measuring the relative astrometry of the 1.85~arcsec A--B pair with an uncertainty of 234~$\mu$as. Here, we describe subsequent phase-tracking testing, preliminary sensitivity simulations, and planned instrumental upgrades aimed at extending this mode to faint off-axis science targets.
N. Anugu, J. Monnier, D. Gies et al.· Optical and Infrared Interfe...· 0 citations
Estimations of stellar angular diameters can be determined based on the surface brightness-colour relation (SBCR) and photometry. In the context of the PLATO space mission, the SBCR is considered to be an independent empirical alternative for estimating the stellar radii of FGK stars.
We implemented a homogeneous approach, not only for calibrating the SBCR for FGK-IV/V stars, but also for determining their fundamental parameters. This made it possible to reliably place the stars on the Hertzsprung-Russell (HR) diagram and to study their impact on the SBC relations.
We performed interferometric observations of 18 quiescent FGK-IV/V stars in the Gaia magnitude range of . For the first time, we used three different interferometric instruments operating in the , , and bands to measure the polychromatic limb-darkened angular diameters. In parallel, by using public domain spectra, we were able to estimate the stellar parameters (T_ . 3.088 łeq G łeq 5.498 R H K łog g, and Z) by using the open Python tool iSpec
We achieved an average accuracy of 2.3% for the limb-darkened angular diameters based on polychromatic observations. However, we observed that our SBCR relation does not follow the calibration of the SBC relations in Gaia found in the literature. Furthermore, we found that the łog g and Z parameters have no impact on this relationship. Given the characteristics of our sample of quiescent stars, it constitutes an ideal set of targets for conducting a new SBCR calibration within the framework of the PLATO space mission. In this context, we report a SBCR calibration with σ_ RMS = 0.012, 0.009, and 0.009 in the G, G_ BP , and G_RP Gaia bands, respectively.
This work is part of a series of papers reporting the first results obtained using a polychromatic approach to measure angular diameters, employing a fully homogeneous methodology for determining the fundamental parameters of stars and measuring the limb-darkened angular diameters
R. I. Ibañez Bustos, D. Mourard, N. Nardetto et al.· Astronomy & Astrophysics· 0 citations
Long-baseline optical interferometry provides spatially resolved observations of close binaries, complementing spectroscopic and photometric constraints on stellar parameters.
With the capabilities of the new visible CHARA/SPICA instrument and the multiple spectral band operation of CHARA, our goal is to resolve orbits of short-period binaries and develop a robust framework for combining interferometric, spectroscopic, and photometric observations into a single consistent model.
For our target sample, we selected suitable binaries based on brightness, angular separation, and orbital properties based on the expected performance of the CHARA/SPICA instrument. As a case study, we analysed the bright eclipsing binary β Aurigae, composed of two slightly evolved A1 stars. We combined new interferometric observations of code to simultaneously fit all observables using MCMC sampling. We performed a detailed analysis of the noise statistics of each data set and in the end we adopted a profile likelihood approach to account for underestimated noise and systematics. obtained with CHARA/SPICA, MIRC--X, and MYSTIC with archival MIRC data, radial velocities, and light curves. We first derived astrometric positions from interferometric observables and computed an orbital solution. Afterwards, we implemented a unified model, capable of tying interferometric modelling with the ellc
We derived a consistent orbital and physical solution for through joint modelling. The inclusion of interferometric data tightly constrains the angular semi-major axis and inclination. Using profile likelihood to account for the different intrinsic levels of uncertainty of the fundamentally different observables, we derived the masses of the two stars, M_1 = 2.359 ± 0.005, and M_2 = 2.293 ± 0.004, their radii R_1 = 2.752 ± 0.002,̊sun and R_2 = 2.622 ± 0.002,̊sun, and the distance to the binary, d = 24.30
J. Jonák, D. Mourard, J. Monnier et al.· Astronomy & Astrophysics· 0 citations
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