Vestiges is the first volume in Laurence Suhner’s QuanTika trilogy. Although Suhner writes in French, I was able to find an English translation of at least this first volume.
Having failed to terraform Mars, humanity transfers its colonizing enthusiasm to the nearby AltaMira system. Only six and a half light years from the Solar System, AltaMira is within reach of sub-light starships. Like the Solar System, it has an Earth-like world with a breathable atmosphere in the double star’s habitable zone. More or less. The “or less” is thanks to an eccentric orbit that dooms the world to snowball status for most of its year.
It is also the site of humanity’s first contact with an alien civilization — or rather, the relics of one. A structure dubbed the Great Arch orbits Gemma and is clearly artificial. It is also seemingly inert and impenetrable. Its secrets have been well hidden. That is about to change.