If I am deleting the object in non-versioned bucket, can there be delete marker ?

Hello.

If you delete an object in an S3 bucket that does not have versioning enabled, the object will be deleted as is.
Deletion markers are never created.
Enable versioning if you need deletion markers.
https://docs.aws.amazon.com/AmazonS3/latest/userguide/DeleteMarker.html

If versioning is not enabled and you delete the objects from bucket, they are permanently deleted without creating any delete marker.