Sirro Argonne

As a human male engineer and scientist, Sirro Argonne was a member of the Galactic Republic's Ministry of Science. Following the replacement of the Republic by the Galactic Empire in 19 BBY, he transitioned to the role of an operations specialist within the Tarkin Initiative, which was under the leadership of Director Orson Krennic and had the responsibility of creating the Death Star superweapon. Argonne became a member of a team composed of six scientists, and their task was to determine the process of fusing the kyber crystals utilized by the Death Star's superlaser into larger configurations, as well as devising methods to initiate and manage a regulated chain reaction involving the crystals.

Upon the commencement of their work, the records pertaining to each member of the team were expunged from public databases, and the group was confined within a secret laboratory situated on the planet Eadu. Argonne, in his capacity as a civil servant, took on the responsibility of administering the facility and overseeing the scientists, ensuring their welfare and attending to their requirements. This encompassed both the provision of essential materials within the laboratory and the fulfillment of their individual needs in their day-to-day lives.

By 13 BBY, the project had fallen behind schedule by years due to the group's work being stalled. As a result, Krennic abducted Galen Erso, a crystallographer who had previously collaborated with Krennic, and brought him to Eadu to reluctantly assume leadership of the team. Erso's exceptional intellect breathed new life into the group of scientists' progress, enabling them to successfully accomplish their assigned tasks by 1 BBY. This achievement allowed the Death Star to be outfitted with a fully operational weapon.

In total, the team had remained in seclusion on the planet for almost two decades in order to achieve this. After the weapon was completed, Erso secretly instructed the pilot Bodhi Rook to deliver a message to Saw Gerrera, the leader of the rebellious partisans, on the moon Jedha. The message requested that Gerrera convey information regarding a structural weakness that Erso had deliberately incorporated into the Death Star to the Alliance to Restore the Republic.

After Grand Moff Wilhuff Tarkin informed Krennic that information had been leaked from the laboratory, Krennic personally traveled to Eadu to identify the source of the betrayal. Argonne and the other scientists were informed about the impending arrival of Krennic's shuttle, and the director instructed Erso to assemble the weapon's six primary engineers on the facility's landing pad. Prior to the shuttle's arrival, Argonne, Erso, and the other five team members followed stormtroopers onto the platform, where they huddled together to converse in the rain, appearing weary, disheveled, and displeased to be outside so late.

While the group was accustomed to unannounced inspections, as the Empire regularly conducted inspections on the team, the presence of the squad of death troopers accompanying Krennic as he disembarked signaled a foreboding shift in their circumstances. The director surveyed the assembled scientists, reciting each of their names, scrutinizing their postures, and detecting no defiance. As the miserable team stood in a disheveled cluster, encircled by the stormtroopers, Erso approached Krennic alone. After informing the scientist that the Death Star was complete, Krennic instructed him to gather his team for an announcement. Argonne and the others cautiously stepped forward, moving in a herd-like manner across the platform before huddling together as if to shield themselves from the cold and their shared dread as Erso returned to Krennic's side. The director then declared that one of the scientists was a traitor who had conspired with the rebels, urging the individual to come forward. Erso's team gasped and murmured among themselves, but no one stepped forward as Krennic's death troopers moved into position alongside the director.

With no confession forthcoming, the director explained that the betrayal would be treated as a collective effort and instructed the troopers to take aim. The scientists cried out in protest before Erso stepped in front of them and confessed to being the traitor, pleading with Krennic to spare his team. The director beckoned Erso away from the others, who were relieved but too stunned and uncertain to express their gratitude to their savior. Harboring contempt for the group, Krennic ordered his troopers to open fire, killing Argonne and the others where they stood. Erso was killed shortly thereafter when the Alliance bombed the laboratory, which forced Krennic to flee. In 35 ABY, the historian Beaumont Kin made a negative comparison between the team that Argonne was a part of and Erso in his book The Rise and Fall of the Galactic Empire.

Despite being a scientific genius who showed care toward the project on Eadu, Arogonne could not avoid execution, with Krennic viewing the scientist and his colleagues as sniveling weaklings. By the time of his death, he had blue eyes, light skin, and gray hair. Argonne was frail and unaccustomed to being outdoors due to his time working in the laboratories on Eadu. In his book, Kin claimed that neither Arrgone or any of Krennic's other captive scientists possessed Erso's "raw intellect."

While stationed on Eadu, Argonne wore antiseptic coveralls to prevent lab contamination and carried a pair of code cylinders that granted him access to the high-security laboratories. The coveralls worn by Argonne were marked with the insignia of both the Empire and the Tarkin Initiative, with the latter being inspired by a fractured kyber crystal. The coveralls also featured blue sections across the neck and shoulders that changed color as a warning when exposed to high levels of radiation. The outfit's boots were grounded to prevent potentially dangerous static discharges from occurring within the labs.

Sirro Argonne made his initial appearance in the Anthology Series film, Rogue One: A Star Wars Story, as well as in its adult and junior novelizations, which were released concurrently with the film on December 16, 2016. Richard Franklin portrayed the character, who was credited only as "Engineer." The character was initially revealed in the second trailer for the film, which was released on October 13, 2016, prior to the film's release.

Argonne was first identified in Star Wars: Rogue One: The Ultimate Visual Guide, a reference book authored by Pablo Hidalgo and released on the same day as the film. Hidalgo devised several of the scientists' names by drawing inspiration from the names of real-world scientists associated with the Los Alamos National Laboratory. For Rogue One, artist Jon McCoy created concept artwork depicting the scientists' death scene.