Color–Surface-Brightness Relations for the Roman GBTDS: Interferometric Diameters on a Landolt Photometric Backbone
| Program ID | 19043 |
|---|---|
| Science Category | Exoplanets & Exoplanet Formation |
| Program Type | Analysis |
| Category | Small |
| Principal Investigator | Tabetha Boyajian |
| PI Institution | Louisiana State University |
| Co-Investigators |
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| Abstract | Color–surface-brightness relations (CSBRs) connect a source star's broadband color to its angular diameter, enabling inference of the angular Einstein radius and hence exoplanet masses from gravitational microlensing. The dominant limitation in modern CSBR calibration is not interferometric precision but photometric systematics from cross-system transformations and zero-point inconsistencies. We propose to construct the first CSBRs calibrated natively in the Roman/WFI photometric system, anchored to interferometric calibrators that overlap with Landolt photometric standards. Because interferometrically measured stars are far too bright for direct Roman observation, we place calibrators on the Roman system via synthetic photometry computed from Roman/WFI throughput curves, reducing fractional angular diameter errors by nearly a factor of three relative to transformation-based approaches. Deliverables include CSBR coefficients in multiple Roman color combinations with full covariance matrices and reddening-correction guidance optimized for GBTDS pipelines. |