Sivarani Thirupathi

Associate Professor , Indian Institute of Astrophysics, Bengaluru, India
PhD - A and F stars with circumstellar dust
Research interests:   Metal poor stars, Chemical evolution of the early Galaxy,  Resolved stellar population , AGB,  post-AGB and Proto 
planetary Nebulae , Exo-planet host star  properties, Automated  pipelines for optical and NIR spectroscopy. Datamining of  astronomical surveys.  High resolution spectrographs calibration and modelling.

Research experience: 
Past Students
Anantha Chanumolu - 2016 - Characterization and calibration of fiber fed spectrograph for precise radial velocities and chemical abundances.
Currently a postdoc at Max Planck Institute for solar system research, Göttingen

Current Students
Susmitha Rani Antony - Study of stellar relics from the Halo 
Avrajit Bandyopadyay - Globular cluster and Halo connection
Devika Divakar - Studies of Milkyway satellites in the era of TMT
Athira Unni - Exoplanet host star properties

Arun Surya - Hanle Echelle spectrograph, data pipeline, TMT-WFOS flexure compensation modelling, fiber target allocation 

Research interest

Near field cosmology-  Extreme metal poor (EMP) stars ([Fe/H]  < -2.5) of the Milkyway are thought to have formed during the first one billion years of the Universe. They are one of the most metal poor and pristine systems. A detailed chemical composition of EMP stars can help constrain the first supernovae that exploded in the Galaxy and the IMF of the First stars. We study the EMP stars of the Galaxy  using large spectroscopic surveys (e.g. SDSS) and detailed chemical abundances using high resolution spectroscopy, to constraint the early supernovae that polluted the ISM. We also study the possible connection between the EMP stars of the Halo, satellite galaxies and halo Globular clusters.

Exoplanet host stars - There exists a well known correlation of the exoplanet host star metallities and the probability of hosting Jupiter like planets, supporting the core accretion model of planet formation. We study the connection between the properties of the host stars (e.g. host star metallicities, abundances and binarity) and the nature of  planets hosted by them to understand the planet formation process. We study the SDSS-MARVELS and KEPLER samples to study this. MARVELS survey has very few selection bias in their samples and suitable to address these issues.

Spectrograph modelling and model based calibration - In the recent years, there has been a major progress in the design and the stability of astronomical spectrographs.  However, one of the limiting factors of the precise radial velocity measurements is wavelength calibration of the data. Laser combs will  tremendously improve this situation, however there are several practical difficulties in implementing laser combs. We have developed a model based calibration approach, where the optical design along with an optimization code that is used to match the observed data by changing set of spectrograph parameters. This way we derive a complete wavelength map on the detector.