Title : Gamma-Ray Bursts (GRBs) as electromagnetic (EM) counterparts of Gravitational Wave (GW) sources

Abstract

Gamma-Ray Bursts (GRBs) are the brightest explosions in the Universe since the Big Bang. We have comprehensive knowledge about the GRBs, but there are many open questions even after fifty years of the first detected GRB, especially about the prompt emission phase. The detection of gamma-ray burst GRB 170817A by Fermi-GBM, coinciding with gravitational wave (GW) GW170817, is one of the extraordinary discoveries in the history of the multimessenger era. It is not only the first binary neutron star (BNS) merger detected by the advanced (LIGO-Virgo) GW detectors; it is the only GW detection with a confirmed electromagnetic (EM) counterpart. The Fermi Gamma-ray Burst Monitor (GBM) is an all sky monitoring instrument sensitive to photon energies from 8 keV to 40 MeV. Its capabilities makes it ideal for providing simultaneous gamma-ray observations of gravitational-wave transients. Fermi-GBM continues to look for similar multimessenger detections through on-board triggers as well as subthreshold searches for weak transients, performed both in high-time-resolution continuous data and in targeted follow-ups of gravitational-wave events. In this talk, I will present an overview of GRBs and recent results from targeted and subthreshold searches as a counterpart of GW events.

Title : Hot Jupiter Exoplanets: The Enigmatic Giants of Astrophysics

Abstract

Since the discovery of the first exoplanet, 51 Pegasi b, Hot Jupiters (HJs)—Jupiter-like exoplanets orbiting close to their host stars—have remained a central focus in exoplanetary science. Unlike planets in our solar system, these unique systems allow us to study them directly through their infrared emission. Due to intense stellar irradiation, Hot Jupiters exhibit extremely high temperatures, resulting in distinct emission spectra originating primarily from their day-side hemispheres, especially in tidally locked systems. Analyzing these emission spectra provides valuable insights into the temperature structure and chemical composition of these intriguing exoplanets. However, the overlap between planetary and stellar emissions poses a persistent challenge for planetary atmospheric modeling. Additionally, the strong day-night atmospheric flow, driven by the extreme temperature contrast between hemispheres, introduces variability in the observed emission spectra. Another intriguing feature of Hot Jupiters is their larger observed radii compared to Jupiter; a phenomenon known as the radius inflation problem. In this talk, I will explore these fascinating questions surrounding Hot Jupiters, using fundamental physics concepts to unravel the mysteries of these extraordinary worlds.

Title : Echoes of the Ancient Earth: A Quarter Century of Exploring the Vindhyan Basin’s Secrets

Abstract

The first known animal life on Earth dates back to 630 million years. However, in 1998, a couple of fossil discoveries shook the geoscience world with their spectacular claims of the presence of advanced animal life in rocks of the Vindhya mountains that were generally considered to be older than 1100 million years. These findings sparked intense controversies about their legitimacy and the host rocks' ages. We took up the challenge of dating these rocks deposited in India's largest Proterozoic sedimentary basin. In the last 25 years, we have not only been able to resolve the chronology of the Vindhyan Supergroup, but also made many significant contributions to the study of regional stratigraphy and environment, ocean chemistry and tectonics during the Proterozoic. In the talk, I shall share some of our important findings.