Solar atlas revised

Abstract

Context. Present knowledge of the solar spectrum is limited because it is very difficult to observe the integrated solar spectrum at high resolution. The reflected solar light from asteroids has been shown to provide a relatively straightforward integrated and unmodified solar spectrum. Aims. We exploit this methodology to improve our knowledge of solar photospheric line positions both in terms of line number and precision with respect to the available solar line atlas. Methods. We used the DAOSPEC program to measure solar line positions automatically in high signal-to-noise spectra of Ceres obtained with HARPS at the 3.6 m ESO telescope. The line positions were then verified with the solar HARPS spectra of Ganymede and daylight as well as with a new FTS solar spectra. Results. A new atlas with 2334 lines in the range 4000−6859 A is provided. The new atlas is consistent with that based on FTS solar spectra but the new line list improves the precision of individual lines by at least a factor 3−5. Conclusions. The new atlas provides a benchmark for 3D models of the solar photosphere and can be used to trace possible line drifts related to solar activity or to calibrate space and ground spectrographs.