# FAQs

## How can I request a photometric system to be added?

Users can request the addition of other photometric systems by raising an issue via GitHub. The main conditions for adding a new system are the following:

Only passbands that are fully enclosed in the Gaia BP/RP wavelength range [330, 1050] nm can be reproduced.

Requests need to be properly justified. An example: it would be pointless to include a specific set of passbands that is used at a given telescope to approximate the JKC or SDSS systems. Synthetic magnitudes/fluxes (standardised or non-standardised) in these systems can be already obtained with GaiaXPy. On the other hand, it would be useful to include a set of passbands adopted by an existing or forthcoming survey that intends to provide magnitudes in its own “natural” photometric system, or a set aimed at tracing a specific feature/characteristic of the available XP spectra, not covered by already included passbands.

The newly added systems will be publicly available to all GaiaXPy users.

The new system to be added is specified as follows:

one CSV file per passband, containing the following columns: wavelength in nm or Angstrom, total response in arbitrary units.

it must be clearly specified if the transmission curves are photonic curves or energy curves (see, e.g., Bessell & Murphy 2012).

it must be clearly specified if the desired magnitudes are VEGAMAG or AB mag.

a reference for the source of all the above info (especially the transmission curves) must be provided.

## GaiaXPy can receive pandas DataFrames, what type of frame is it expecting?

GaiaXPy expects to receive a pandas DataFrame with at minimum the columns and types:

source_id (int)

bp_n_parameters (int)

rp_n_parameters (int)

bp_coefficients (NumPy ndarray)

bp_coefficient_errors (NumPy ndarray)

bp_coefficient_correlations (NumPy ndarray)

rp_coefficients (NumPy ndarray)

rp_coefficient_errors (NumPy ndarray)

rp_coefficient_correlations (NumPy ndarray)

bp_basis_function_id (int, only required if truncation=True)

rp_basis_function_id (int, only required if truncation=True)

If strings are present in the data, the program will fail.

The NumPy ndarrays should be 1-dimensional arrays. In the case of bp_coefficient_correlations and rp_coefficient_correlations, both 1-dimensional and 2-dimensional arrays are accepted. If a 1-dimensional array is passed, the program will use the function array_to_symmetric_matrix to transform the array. If a 2-dimensional array is received, no changes will be applied. This 2-dimensional array should have dimensions (55, 55).