  Context. The sterile neutrino is an excellent dark matter candidate, which
can be searched for in a wide range of astrophysical sites. It has previously
been shown that the optimal search strategy is to consider dwarf galaxies
belonging to the Milky Way. Aims. We search for line emission from decaying
dark matter. Methods. We analyse publicly available Chandra X-ray observations
of the dwarf galaxy Draco. Results. The Draco and blank sky (background)
spectra are nearly identical in shape, which allows us to conclude: i) Dwarf
spheroidals are ideal for studying dark matter X-ray emission since the
baryonic noise is impressively low, ii) there is very little room for line
emission, which leads to constraints in the mass-mixing angle parameter space
of the sterile neutrino. We compare the standard flux derivation method to a
very conservative rebinning approach. The resulting constraints are strongly
dependent on the chosen method.
