"Can I double spend this transaction?" as long as the transaction is unconfirmed you can try to make a new transaction with the same transaction-details but a noticeable higher fee. then you must hope that your new transaction (with the higher fee) will be executed before your b9d6d...-transaction will be executed. if this works the result would be that the b9d6d...-transaction will never be executed in future because there are not enough funds on your 1GDvWJUd7Hy...-adress. did you mean this by writing "double spend"?