Sivarani Thirupathi

Research experience:

2020 - Present, Professor, Indian Institute of Astrophysics
2014 - 2020, Associate Professor, Indian Institute of Astrophysics
2009 - 2014, Reader, Indian Institute of Astrophysics, Bangalore, India
2008 - 2009, MARVELS SDSS-III postdoc, University of Florida
2004 - 2008, JINA Research Associate, Michigan State University
2003 - 2004, Visiting fellow, IUCAA, Pune
2002 - 2003, INAF postdoc, Osservatorio Astronomico di Trieste, Italy
2001-2002, CNRS postdoc, Université de Montpellier-II , France
2000 - PhD Indian Institute of Astrophysics

Research interest

Galactic archeology- 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. The 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 - 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.

Instrumentation projects

Hanle Echelle Spectrograph

Wide field optical spectrometer for the 30-m telescope

High resolution optical spectrometer for the 30-m telescope

SCALES - Santa Cruz Array of Lenslets for Exoplanet Spectroscopy

INSIST - Indian Spectroscopic and Imaging Space Telescope

ExoWorlds

Past Students & Postdocs

Anantha Chanumolu - 2016 - Characterization and calibration of fiber fed spectrograph for precise radial velocities and chemical abundances. Instrument scientist at SRON, Netherlands and Currently at ESA, Netherlands

Arun Surya - Hanle Echelle spectrograph, data pipeline, TMT-WFOS flexure compensation modelling, fiber target allocation Currently a postdoc at University of California at San Diego

Susmitha Rani Antony - Study of stellar relics from the Halo, Currently a postdoc

Avrajit Bandyopadyay - Globular cluster and Halo connection , Currently a post-doc at Univ. Florida

Current Students:

Devika Divakar - Studies of Milkyway satellites in the era of TMT

Athira Unni - Exoplanet host star properties, submitted

Pallavi Saraf - Metal poor stars and Globular clusters

Manjunath Besta - Astronomical instrumentation

Akhil Jaini - Exoplanet studies observations and modelling (currently at Swinburne)

Parvathy (co-supervising) - Sun and solar system objects in the context of exoplanets