Each instrument has its own set of filters (wavelength bands) that measure light in slightly different ways. For example:JWST, Roman, the Euclid, the Hubble Telescope.
The libraries researchers used include:
- CALSPEC (HST calibration stars)
- IRTF and X-Shooter Spectral Libraries
- E-IRTF (extended version for cooler stars)
Each library covers different temperature, metallicity (chemical composition), and luminosity classes — together they give a wide coverage of the HR diagram.
Synthetic magnitude is calculated as
F(λ): star’s flux (how much light it emits per wavelength).
T(λ): filter transmission function, show how transparent the filter is at each wavelength.
Continuous Piecewise linear transformation function is calculated as
It is used for fitting or converting magnitudes between different near-infrared (NIR) filters — such as those from JWST, Roman, and Euclid telescopes
Researchers-
- Collected star spectra from multiple libraries
- Simulated how each star looks through each telescope’s filters
- Built mathematical relationships color–magnitude equations
- Used regression to fit coefficients and calculated error
- Checked across star types (HR diagram)
- Applied to TRGB method (red giants branch) measures distance
https://iopscience.iop.org/article/10.3847/1538-3881/adfddb#ajadfddbs1
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