Annual Report_Abridged - Second Version - FINAL

14 RESEARCH AT IUCAA StellarAstrophysicsandCosmicDistanceScale The IUCAA 'STARS group led by Anupam Bhardwaj is interested in stellar evolution and pulsation across the Hertzsprung-Russell diagram, Galactic archaeology, resolved stellar populations in star clusters and nearby galaxies, and near- field cosmology. Dr. Anupam Bhardwaj, new faculty member at IUCAA, works on precision stellar astrophysics and the cosmic distance scale using multi-wavelength photometric and spectroscopic observations of classical pulsating variable stars. The current focus of research in stellar group is on improving the calibration of stellar standard candles in the first rung of the cosmic distance ladder used to determine the present expansion rate of the Universe. Dr. Bhardwaj and his group uses Cepheid, RR Lyrae, and Mira variable stars as stellar population tracers for Galactic archaeology and near-field cosmology with observational data from 4-8 m class telescopes. The group is involved in several multi-wavelength time-domain surveys such as VVV, ZTF, upcoming LSST, and in specific projects with TESS and Gaia space missions. On the theoretical front, ongoing efforts include stellar evolution and pulsation modeling with the Modules for Experiments in Stellar Astrophysics (MESA), open-source 1D stellar evolution code. PhysicsofCompactObjects Debarati Chatterjee and her research group at IUCAA are involved in studying Neutron Stars, ultra-dense compact objects which show a myriad of extreme properties and serve as cosmic laboratories to investigate fundamental Physics. Their strong gravity can bend space-time significantly, and their collisions or perturbations can result in strong gravitational wave emission. The recent ground-breaking detection of gravitational waves from Neutron Stars has opened up a new window to the Universe and a novel method to probe their interior. The team is developing theoretical models to describe the interior of Neutron Stars, consistent with state-of-the-art information from multidisciplinary domains, such as Nuclear, Particle and Condensed Matter Physics from terrestrial experiments and multimessenger astrophysical data. In the past few years, several investigations were conducted by them to look for signatures of the internal composition of Neutron Stars in gravitational wave emission from unstable oscillation modes. The studies demonstrated how our understanding of dense matter properties can be significantly improved using signals from such oscillations, in both isolated or binary systems, with current or planned future generation gravitational wave detectors. They also investigated how such detections may allow us to distinguish between Neutron Stars and other stable families of compact stars or probe the nature of possible phase transitions or presence of dark matter. Other works also demonstrated how tidal heating during Neutron Star mergers could be a novel probe of the presence of exotic particles in their interior. Quantum Metrology and Precision Measurements Since the conceptualization of Quantum Mechanics, we are now in an era of a second quantumrevolution, when several countries in the world, including India, are advancing cutting- edge quantum-enhanced technologies in