Astrophysics Seminar

General Coordinates Network (GCN) is a collaborative platform operated by NASA to facilitate the quick sharing of alerts and communication within the astronomy research community regarding high-energy, transient, and multi-messenger phenomena. GCN has introduced the GCN Unified Schema, the foundation for the new GCN Notices, and employs a JSON format for easy machine readability and accessibility through an open-source repository. For GCN Circulars, Neural Topic Modeling with BERTopic is used to track the evolution of different observation types over the three decades of GCN. The large-language model has been utilized to extract redshift information in tabular form and has the potential for further use in extracting useful information from the database. Focusing on one of the transients, short GRBs, prompt emission is studied using the model of a multi-color blackbody, which is interpreted as the emission from a non-dissipative photosphere considering a power law jet structure and the viewing geometry of the jet. Using this interpretation, we infer that nearly 57%(18%) of the sGRBs in our sample are observed within (or along the edge of) the jet core. Using this physical interpretation, a narrow jet core with a median of ~ 3 degrees and a power-law index of 1.3 - 2.2 as a decreasing Lorentz factor profile for the jet structure is deduced. This suggests the rate of coincident detections of bright short GRBs with gravitational waves to be 0.19 - 2.87 events/yr.  Lastly, 8 long GRBs with black holes as their central engine identified in 11 years of Fermi data will be presented.