Few independent detections of a weak X-ray line at an energy of \sim 3.5 keV seen toward a number of astrophysical sites have been reported .
If this signal will be confirmed to be the signature of decaying DM sterile neutrino with a mass of \sim 7.1 keV , then the cosmological observables should be consistent with its properties . In this paper we make a coupled treatment of the weak decoupling , primordial nucleosynthesis and photon decoupling epochs in the sterile neutrino resonant production scenario , including the extra radiation energy density via N _ { eff } .
We compute the radiation and matter perturbations including the full resonance sweep solution for \nu _ { \alpha } / { \bar { \nu } } _ { \alpha } \rightarrow \nu _ { s } flavor conversion in the expanding Universe . We show that the cosmological measurements are in agreement with subdominant Dark Matter sterile neutrino resonant production with following parameters ( errors at 95 % CL ) : mass m _ { \nu _ { s } } = 6.08 \pm 3.22 keV , mixing angle \sin ^ { 2 } 2 \theta < 5.61 \times 10 ^ { -10 } , lepton number per flavor L _ { 4 } = 1.23 \pm 0.04 ( L _ { 4 } \equiv 10 ^ { 4 } L _ { \nu _ { a } } ) and sterile neutrino mass fraction f _ { \nu _ { s } } < 0.078 . Our results are in good agreement with the sterile neutrino resonant production parameters inferred in Ref . [ [ 62 ] ] from the linear large scale structure constraints to produce full Dark Matter density .