Solid confirmation of the broad DIB around 864.8 nm using stacked <i>Gaia</i>–RVS spectra

Context. Studies of the correlation between different diffuse interstellar bands (DIBs) are important for exploring their origins. However, Gaia –RVS spectral window 846 and 870 nm contains few DIBs, strong DIB at 862 being only convincingly confirmed one. Aims. Here we attempt to confirm existence a broad around 864.8 estimate its characteristics using stacked spectra large number stars. We study correlations two DIBs ( ? 862) 864.8), as well extinction. Methods. obtained medium (ISM) absorption by subtracting stellar components templates constructed from real high Galactic latitudes with low extinctions. then ISM in coordinates (?, b ) – pixelized HEALPix scheme measure DIBs. The spectrum is modeled profiles Gaussian Lorentzian 864.8, linear continuum. report fitted central depth (CD), wavelength, equivalent width (EW), uncertainties Results. obtain 8458 total, which 1103 (13%) have reliable fitting results after applying numerous conservative filters. This work first kind fit simultaneously cool-star spectra. Based on these measurements, find that EWs CDs correlated each other, Pearson coefficients r p 0.78 0.87, respectively. full half maximum (FWHM) estimated 1.62 ± 0.33 compares 0.55 0.06 862. also vacuum rest-frame wavelength be 0 = 864.53 0.14 nm, smaller than previous estimates. Conclusions. solid confirmation based an exploration estimation FWHM. very shallow. That correlates better E BP ? RP 864.8. could strongly overlap contributes skew profile.