Hayden Panettiere Honored by 'Heroes' Stars During Cast Reunion

Hayden Panettiere's death gave her former castmates a reason to get together ... inspiring her former "Heroes" co-stars to celebrate her life and lasting impact on Hollywood and beyond.

Jimmy Jean-Louis -- a veteran actor who played a recurring character known as "The Haitian" in 32 episodes of the beloved superhero show -- shared photos from the gathering ... including a big group photo that featured stars like Jack Coleman, Masi Oka and Adrian Pasdar.

Madeline Zima -- who recently spoke with us about Hayden's life and legacy -- attended ... and Zachary Quinto, who played the infamous villain Sylar on the show, and Sendhil Ramamurthy appeared via video call.

Notably absent from the gathering was Milo Ventimiglia ... a main cast member on the program with whom Hayden was in a short-lived relationship. He's been radio silent in the days since Hayden's death.

In his post, Jean-Louis wrote that the reunion was "deeply emotional" ... filled with sadness, love and gratitude.

He adds the cast focused on "the beautiful moments shared and the lasting impact of a life that touched so many. Au revoir Hayden."

As we reported ... Hayden was found unresponsive in a Greenville, South Carolina, residence last week ... first responders attempted to resuscitate her, but she was pronounced dead.

Local authorities and the Drug Enforcement Agency are looking into her death ... and her mother, Lesley Vogel, is convinced her boyfriend Brian Hickerson is "culpable."

Hayden appeared on 75 episodes of "Heroes" as Claire Bennet -- a cheerleader who can heal from nearly any injury.