MSV-2035 Astronomy Document - Inside Design - FINAL - FINAL

Astronomy & Astrophysics 45 production in stars is common. Using data from large spectroscopic surveys such as GALAH and LAMOST, combined with astrometric data from Gaia, and astroseismology data from Kepler space telescope, they made a systematic investigation of Li enhancement in evolved stars and found the enhancement to be common among the low-mass giants associated with He-core burning phase, also referred to as Red Clump stars. Observational evidence for Li enhancement during the helium-flashing phase was established. This result is the first observational evidence of the theory developed in 1960s for converting an inert, electron-degenerate He-core into a fully convective He-burning core by a series of core He-flashes, a phase that lasts for about 2million years. Combining ground based high resolution spectroscopy and astrometry of stars in the Solar neighbourhood (within 200 pc) from the Hipparcos space mission the Galactic disc was decomposed into thin and thick discs. It was found that the stars in the thick disc are old (~ 8 - 10 Gyrs), metal-poor ([Fe/H] ~ -0.6) and found to have distinct kinematic motions and chemical composition different from that of thin disc population. The thick disc population is believed to be the result of amajor merger of ametal-poor dwarf galaxywhen theMilkyWaywas just 1-2Gyrs old. An extensive study was carried out based on 300,000 stars using the SDSS-DR7 database and it was shown that carbon production happened in the early Galaxy, through massive stars, either during the wind or through faint SNe. Supporting evidence was found in the study of carbon abundance in Bootes dwarf galaxy. Similar galaxies are thought to be the first galaxies formed in the Universe and building blocks of our Galaxy halo. These results have implications on the early chemical evolution, feedback and critical metallicity for the first lowmass star formation and so on. 4.1.7 Stellar andExoplanetAtmospheres Application of radiative transfer to understand line formation and polarisation has been a core area in theoretical studies of the stellar and solar atmospheres. Polarised spectral line formation in solar and stellar atmospheres is one of the front-line areas that is being pursued. Polarisation of spectral lines provides us with an important diagnostic tool to decipher the thermal, magnetic, and dynamic nature of the solar and stellar atmospheres. For this purpose, quantum and classical theories of light scattering on atomic systems were formulated and efficient numerical methods were developed to solve the concerned polarised radiative transfer equation. It is now increasingly clear that the atmospheres of the young, self-luminous extrasolar giant planets imaged to date are dusty. Planets with dusty atmospheres may exhibit detectable amounts of linear polarisation in the near-infrared. The asymmetry required in the thermal radiation field to produce polarisation may arise either from the rotation- induced oblateness or from surface inhomogeneities, such as partial cloudiness. Using a self-consistent, spatially homogeneous atmospheric model and a multiple scattering polarisation formalism for this class of exoplanets, it is shown that polarisation of the order of 1 per cent may arise due to the rotation-induced oblateness of the planets. Polarised radiation from self-luminous gas giant exoplanets, if detected, provides an additional tool to characterize these young planets and a newmethod to constrain their surface gravity andmasses. A state-of-the-art numerical code that generates new grids of transmission spectra for hot Jupiters was recently developed by astronomers at IIA. The synthetic spectra obtained through the detailed modelling, were compared with the available observed spectra obtained by using HST and Spitzer Space telescope. The JWST, the upcomingARIEL space telescope and the TMT will be able to obtain high resolution transmission spectra of exoplanets during transit MEGA SCIENCE VISION-2035