pertaining to or occurring near the sun, especially applied to such risings and settings of a star as are most nearly coincident with those of the sun while yet visible.
Also he·li·ac [hee-lee-ak] /ˈhi liˌæk/.
Origin of heliacal
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Online Etymology Dictionary, © 2010 Douglas Harper