The low-energy electronic recoil spectrum in XENON1T provides an intriguing hint for potential new physics .
At the same time , observations of horizontal branch stars favor the existence of a small amount of extra cooling compared to the one expected from the Standard Model particle content .
In this note , we argue that a hidden photon with a mass of \sim 2.8 keV and a kinetic mixing of \sim 10 ^ { -15 } allows for a good fit to both of these excesses .
In this scenario , the signal detected in XENON1T is due to the absorption of hidden photon dark matter particles , whereas the anomalous cooling of horizontal branch stars arises from resonant production of hidden photons in the stellar interior .