▁In ▁early ▁stars ▁of ▁spectral ▁type ▁O ▁and ▁B , ▁shock s ▁developing ▁in ▁un stable ▁wind s ▁are ▁the ▁likely ▁source ▁of ▁X - ray s . ▁ ▁C ool est ▁M ▁d war fs ▁Bey ond ▁spectral ▁type ▁M 5 , ▁the ▁classical ▁α ω ▁dynam o ▁can ▁no ▁longer ▁operate ▁as ▁the ▁internal ▁structure ▁of ▁d war f ▁stars ▁changes ▁significantly : ▁they ▁become ▁fully ▁con ve ct ive . ▁As ▁a ▁distributed ▁( or ▁α 2 ) ▁dynam o ▁may ▁become ▁relevant , ▁both ▁the ▁magnetic ▁flux ▁on ▁the ▁surface ▁and ▁the ▁topology ▁of ▁the ▁magnetic ▁fields ▁in ▁the ▁cor ona ▁should ▁system atically ▁change ▁across ▁this ▁transition , ▁perhaps ▁resulting ▁in ▁some ▁dis continu ities ▁in ▁the ▁X - ray ▁characteristics ▁around ▁spectral ▁class ▁d M 5 . ▁However , ▁observations ▁do ▁not ▁seem ▁to ▁support ▁this ▁picture : ▁long - time ▁lowest - mass ▁X - ray ▁detection , ▁VB ▁ 8 ▁( M 7 e ▁V ), ▁has ▁shown ▁steady ▁emission ▁at ▁levels ▁of ▁X - ray ▁lum inos ity ▁( L X )   ≈ ▁ 1 0 2 6 ▁erg · s − 1 ▁( 1 0 1 9 ▁W ) ▁and ▁fl ares ▁up ▁to ▁an ▁order ▁of ▁magnitude ▁higher . ▁Com parison ▁with ▁other ▁late ▁M ▁d war fs ▁shows ▁a ▁rather ▁continuous ▁tr end . ▁ ▁Str ong ▁X - ray ▁emission ▁from ▁Her big ▁A e / Be ▁stars ▁ ▁Her big ▁A e / Be ▁stars ▁are ▁pre -