Measuring Diffuse Interstellar Bands with cool stars. An improved line
  list to model the background stellar spectra
  DIBs are ubiquitous in stellar spectra. Traditionally, they have been studied
through their extraction from hot stars, because of their smooth continuum. In
an era where there are several going-on or planned massive Galactic surveys
using multi-object spectrographs, cool stars constitute an appealing set of
targets. From the technical point of view, the extraction of DIBs in their
spectra is more challenging due to the complexity of the continuum. In this
contribution we will provide the community with an improved set of stellar
lines in the spectral regions associated to the strong DIBs at l6196, l6269,
l6284, and l6379. These lines will allow for the creation of better stellar
synthetic spectra, reproducing the background emission and a more accurate
extraction of the magnitudes associated with a given DIB. The Sun and Arcturus
were used as representative examples of dwarf and giant stars, respectively. A
high quality spectrum for each of them was modeled using TURBOSPECTRUM and the
VALD stellar line list. The oscillator strength log(gf) and/or wavelength of
specific lines were modified to create synthetic spectra where the residuals in
both the Sun and Arcturus were minimized. The synthetic spectra based on the
improved line lists reproduce the observed spectra for the Sun and Arcturus in
the mentioned spectral ranges with greater accuracy. Residuals between the
synthetic and observed spectra are always <10%, much better than with
previously existing options. The new line list has been tested with some
characteristic spectra, from a variety of stars, including both giant and dwarf
stars, and under different degrees of extinction. As it happened with the Sun
and Arcturus residuals in the fits used to extract the DIB information are
smaller when using synthetic spectra made with the updated line lists. Tables
with the updated parameters are provided to the community.
