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.