* Orphan gamma-ray burst (GRB) afterglows occur when the gamma-ray emission from a GRB is not directed towards Earth, making the initial burst invisible. However, the afterglow, produced by the interaction of the GRB's blast wave with surrounding material, can be observed.

* Studying orphan afterglows provides valuable insights into GRB physics and their progenitors, and can enhance multi-messenger analyses with gravitational waves.

* The Vera C. Rubin Observatory, with its exceptional sensitivity and wide field of view, is expected to play a crucial role in detecting orphan afterglows.

* The anticipated high volume of alerts from the Rubin Observatory necessitates the use of alert brokers like Fink to filter and categorize events.

* Researchers are developing a machine learning classifier within Fink to identify orphan afterglows based on their distinct light curve characteristics.

* This classifier uses features like the duration, rise and decay rates, color, and fitted parameters of the light curve to distinguish orphan afterglows from other transient events.

* Initial tests using simulated data show promising results, with the classifier effectively excluding most non-orphan events while retaining a significant portion of orphan afterglows.

Reference: Masson, M., & Bregeon, J. (2024). Search for orphan gamma-ray burst afterglows with the Vera C. Rubin Observatory and the alert broker Fink. arXiv preprint arXiv:2412.05061v1.

Acknowledements: Podcast prepared with Google/NotebookLM. Illustration credits: LSST project/NSF/AURA