F 0 , ▁with ▁a ▁large ▁range ▁of ▁lum inos ities ▁developing ▁across ▁spectral ▁class ▁F . ▁Al ta ir ▁is ▁spectral ▁type ▁A 7 V ▁and ▁V ega ▁is ▁A 0 V . ▁Al ta ir ' s ▁total ▁X - ray ▁lum inos ity ▁is ▁at ▁least ▁an ▁order ▁of ▁magnitude ▁larger ▁than ▁the ▁X - ray ▁lum inos ity ▁for ▁V ega . ▁The ▁outer ▁con ve ction ▁zone ▁of ▁early ▁F ▁stars ▁is ▁expected ▁to ▁be ▁very ▁shall ow ▁and ▁absent ▁in ▁A - type ▁d war fs , ▁yet ▁the ▁ac oust ic ▁flux ▁from ▁the ▁interior ▁reaches ▁a ▁maximum ▁for ▁late ▁A ▁and ▁early ▁F ▁stars ▁prov oking ▁investig ations ▁of ▁magnetic ▁activity ▁in ▁A - type ▁stars ▁along ▁three ▁principal ▁lines . ▁Chem ically ▁peculiar ▁stars ▁of ▁spectral ▁type ▁B p ▁or ▁Ap ▁are ▁appreci able ▁magnetic ▁radio ▁sources , ▁most ▁B p / Ap ▁stars ▁remain ▁und et ected , ▁and ▁of ▁those ▁reported ▁early ▁on ▁as ▁producing ▁X - ray s ▁only ▁few ▁of ▁them ▁can ▁be ▁identified ▁as ▁probably ▁single ▁stars . ▁X - ray ▁observations ▁offer ▁the ▁possibility ▁to ▁detect ▁( X - ray ▁dark ) ▁plan ets ▁as ▁they ▁eclipse ▁part ▁of ▁the ▁cor ona ▁of ▁their ▁parent ▁star ▁while ▁in ▁trans it . ▁" S uch ▁methods ▁are ▁particularly ▁prom ising ▁for ▁low - mass ▁stars ▁as ▁a ▁Jup iter - like ▁planet ▁could ▁eclipse ▁a ▁rather ▁significant ▁cor onal ▁area ." ▁ ▁X - ray ▁dark ▁planet / com