argument. Fred I. Palmer, Sr. (Palmer), president and creditor of debtor, Durability, Inc., appeals from a district court order affirming an order of the bankruptcy court holding Palmer’s $500,000 claim against debtor subordinate to a $1,618,331.80 claim asserted by Fourth National Bank and Trust Co. of Tulsa, Oklahoma (FNB). Palmer and FNB are the named defendants in this adversary proceeding brought by the trustee to determine the validity, priority, and extent of defendants’ liens, as well as to avoid certain allegedly fraudulent transfers. We do not, at this time, reach the merits of the issues raised by Palmer, because we hold that our jurisdiction over this premature appeal has not yet been established. See Tuck v. United Servs. Auto. Ass’n, 859 F.2d 842, 844 (10th Cir. 1988) (<HOLDING>), cert. denied, - U.S. -, 109 S.Ct. 1534, 103
recognizing federal courts duty to determine matter of its own jurisdiction sua sponte whenever it becomes apparent that jurisdiction may be lacking holding that a federal court is obliged to determine its own jurisdiction for each case recognizing every federal appellate court has a special obligation to consider its own jurisdiction even if it must do so sua sponte holding that even where subjectmatter jurisdiction may go unchallenged on appeal we have an obligation to inquire sua sponte into our jurisdiction over the matter holding that sovereign immunity issues may be raised sua sponte as they bear on subject matter jurisdiction