J-PLUS: Toward a homogeneous photometric calibration using Gaia BP/RP low-resolution spectra

Aims. We present the photometric calibration of the 12 optical passbands for the Javalambre Photometric Local Universe Survey (J-PLUS) third data release (DR3) comprising 1642 pointings of two square degrees each. Methods. We selected nearly 1.5 million main sequence stars with a signal-to-noise ratio larger than ten in the 12 J-PLUS passbands and available low-resolution (R = 20-80) spectrum from the blue and red photometers (BP/RP) in Gaia DR3. We compared the synthetic photometry from BP/RP spectra with the J-PLUS instrumental magnitudes after correcting for the magnitude and color terms between both systems in order to obtain a homogeneous photometric solution for J-PLUS. To circumvent the current limitations in the absolute calibration of the BP/RP spectra, the absolute color scale was derived using the locus of 109 white dwarfs closer than 100 pc with a negligible interstellar extinction. Finally, the absolute flux scale was anchored to the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) photometry in the r band. Results. The precision of the J-PLUS photometric calibration estimated from duplicated objects observed in adjacent pointings and by comparison with the spectro-photometric standard star GD 153 is similar to 12 mmag in u, J0378, and J0395, and it is similar to 7 mmag in J0410, J0430, g, J0515, r, J0660, i, J0861, and z. The estimated accuracy in the calibration along the surveyed area is better than 1% for all the passbands. Conclusions. The Gaia BP/RP spectra provide a high-quality, homogeneous photometric reference in the optical range across the full sky in spite of their current limitations as an absolute reference. The calibration method for J-PLUS DR3 reaches an absolute precision and accuracy of 1% in the 12 optical filters within an area of 3284 square degrees.