topological star compact space

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A topological space $X$ is said to be star compact if whenever $\mathscr{U}$ is an open cover of $X$, there is a compact subspace $K$ of $X$ such that $X = \operatorname{St}(K,\mathscr{U})$.

$St(K, \mathscr{U})=\bigcup\{U\in \mathscr{U}: U \cap K \neq \emptyset\}$

‎‎‎$ ‎St‎^{n+1}‎‎ (K, \mathscr{U}‎) =‎ ‎\bigcup ‎ \{ U‎ ‎\in‎ \mathscr{‎U} : U ‎\cap St‎^{n}‎‎‎(K, \mathscr{U}‎) ‎\neq ‎\emptyset \}‎‎‎$‎.‎ ‎

‎‎A topological space $X$ is said to be ‎n-‎star compact if whenever $\mathscr{U}$ is an open cover of $X$, there is a ‎finite ‎subset‎ $‎\mathscr{V}‎$ of $\mathscr{U}$ such that $X = \operatorname{St}‎^{‎n‎}‎(‎\bigcup ‎\mathscr{‎V}‎ ‎‎,\mathscr{U})$.

1:‎ I‎ ‎think ‎that‎ star ‎compact ‎is the same ‎1-‎ star ‎compact.‎ Is it right?‎

‎2:‎ Is star ‎compact, ‎$n‎$‎-star ‎compact?‎‎

3: ‎Is ‎there an example that ‎show‎ ‎‎closed ‎subset ‎in‎ star ‎compact ‎space ‎is ‎not‎ star ‎compact?‎‎

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  1. Yes, see Remark 2.1 in the paper “On $\mathcal K$-Starcompact Spaces” by Yan-Kui Song (Bull. Malays. Math. Sci. Soc. (2) 30:1 (2007), 59–64).