Massless particles like photons possess energy and momentum, which gravitate according to general relativity via the stress-energy tensor; this is a foundational principle of physics requiring no citation.
The claim is a fundamental textbook consequence of general relativity (that energy and momentum, including the electromagnetic field energy of photons, act as sources of gravity). None of the retrieved papers specifically test or dispute this standard fact (most are tangential or on entirely different topics like biology or condensed matter), making it a well-established tenet of physics that functions as common knowledge in the context of scientific evaluation.