user: Question: What is the call sign for the radio owned by Astral Media?
Columns: ['Frequency', 'Call sign', 'Branding', 'Format', 'Owner']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['1150 AM', 'CKFR', 'AM 1150', 'news / talk', 'Astral Media']
SQL:

assistant: SELECT "Call sign" FROM "Table" WHERE "Owner" = 'Astral Media';