Star versions of Lindel\"of spaces

Abstract

A space $ X $ is said to be set star-Lindel\"{o}f (resp., set strongly star-Lindel\"{o}f) if for each nonempty subset $ A $ of $ X $ and each collection $ \mathcal{U} $ of open sets in $ X $ such that $ \overline{A} \subseteq \bigcup \mathcal{U} $, there is a countable subset $ \mathcal{V}$ of $ \mathcal{U} $ (resp., countable subset $ F $ of $ \overline{A} $) such that $ A \subseteq {\rm St}( \bigcup \mathcal{V}, \mathcal{U})$ (resp., $ A \subseteq {\rm St}( F, \mathcal{U})$). The classes of set star-Lindel\"{o}f spaces and set strongly star-Lindel\"{o}f spaces lie between the class of Lindel\"{o}f spaces and the class of star-Lindel\"{o}f spaces. In this paper, we investigate the relationship among set star-Lindel\"{o}f spaces, set strongly star-Lindel\"{o}f spaces, and other related spaces by providing some suitable examples and study the topological properties of set star-Lindel\"{o}f and set strongly star-Lindel\"{o}f spaces.