By Gaia DPAC (CU5/DU14)
What it does
Gaia DR3 publishes the mean BP and RP spectra of a star (together XP spectra) as 55 plus 55 coefficients of a continuous representation on Hermite functions (Carrasco et al. 2021; De Angeli et al. 2023). GaiaXPy turns those coefficients into usable products. The function convert samples the internally calibrated BP and RP spectra in pseudo-wavelength. The function calibrate returns the externally calibrated, absolute spectrum on a wavelength grid from about 336 to 1020 nm.
In calibrate, BP and RP are joined into one spectrum by weights across their overlap (Montegriffo et al. 2023). The package also produces synthetic photometry. GaiaXPy is written by the Gaia Data Processing and Analysis Consortium (CU5/DU14) and is open source.
How I used it
I use GaiaXPy calibrate to turn Gaia XP coefficients into calibrated spectra in work in preparation.
The animation
The star is Gaia DR3 5474633394457737216, the star of the galpy card, a red giant chosen at random from the Gaia archive. The 110 coefficients are those published in the Gaia archive. Every weighted Hermite function and every running sum comes from GaiaXPy 2.1.5 convert. The absolute spectrum and the join of BP and RP come from GaiaXPy calibrate.
The heights of the bars are compressed so that the small coefficients show. The small curves in the waterfall are compressed so that their shapes read, and return to their true height as they join the sum. The colours follow the hue of each wavelength, with a dim floor at both ends so that the violet and the near infrared, invisible to the eye, still show. The camera is drawn.