How to get the question posted usernicename?

$content .= sprintf( __( ‘%s added a new answer to %s:’, QA_TEXTDOMAIN ),

_qa_html( ‘a’, array( ‘href’ => qa_get_url( ‘user’, $post->post_author ) ), $author->user_nicename ),

_qa_html( ‘a’, array( ‘href’ => qa_get_url( ‘single’, $question_id ) ), get_post_field( ‘post_title’, $question_id ) )

);

this code is from your subscription.php file, my need is, i want to send an email to the asked question users when he got a new answer, criteria is need to send the question asked user name or nicename or firstname, with some texts, how to get the same from your code?