heliacal
adjective
he·li·a·cal hi-ˈlī-ə-kəl 
: relating to or near the sun —used especially of the last setting of a star before and its first rising after invisibility due to conjunction with the sun
heliacally
hi-ˈlī-ə-k(ə-)lē
adverb 
Did you know?
The word heliacal rose in the mid-16th century. Its source is the Greek word hēlios, meaning "sun." Helios is also the Sun god of ancient Greece. Heliacal often suggests a relationship between a star and the sun as they appear to the human eye in the sky. It is also used in reference to the ancient Egyptian year, which began on the date when Sirius (or the Dog Star) first appeared on the eastern horizon at sunrise. English speakers have referred to this year as the heliacal year or the Sothic year. (Sothic comes from "Sōthēs," the Greek word for Sirius.)
Example Sentences
Recent Examples on the Web There are lots of celestial bodies, but the biggest is Sirius, the dog star, and the 20 days before and the 20 days after its heliacal rising are called the dog days. 
Kevin Fisher-paulson, SFChronicle.com, 10 July 2018
Kevin Fisher-paulson, SFChronicle.com, 10 July 2018 Word History
Etymology
Late Latin heliacus, from Greek hēliakos, from hēlios
First Known Use
1545, in the meaning defined above