Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_40 (date VARCHAR, tournament VARCHAR, runner_s__up VARCHAR)

### Question ###
Which date was the Memorial Tournament held on, when Payne Stewart was runner-up?

### Accurate SQL ###

SELECT date FROM table_name_40 WHERE tournament = "memorial tournament" AND runner_s__up = "payne stewart"