Research Fellow
University of Warwick, UK
"The adventure is not to see new things but to see things with new eyes."
- Claude Bernard -
Current Work
HST COS Ultraviolet spectroscopic survey of DA white dwarfs
Under the Hubble COS snapshot survey program (P.I. Boris Gaensicke), we have carried out a far-ultraviolet spectroscopy survey of 311 DA white dwarfs (WDs) with Cosmic Origins Spectrograph (COS) of HST with the main aim of searching for signatures of planetary debris in intermediate temperature white dwarfs (11 000-30 000 K). We have studied the systematic offsets between the UV-derived parameters (effective temperatures, surface gravities, and masses) with optical photometric (such as Gaia, Pan-STARRS) and spectroscopic studies obtained from the Balmer line fits.
The detailed results from this study is published in MNRAS:
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Contributed authors- Boris Gaensicke, Pier Emmanuel Tremblay, Detlev Koester, J.J. Hermes, David J. Wilson, Odette Toloza, Christopher J. Manser, Mathew Hoskin, Jay Farihi, Seth Redfield
UV fit (in red) to HST COS spectra of DA white dwarfs
I am also a member of the 4MOST survey team (sub-survey S3) working on the 100 parsec survey sample. We are planning to obtain the low-resolution spectra covering the wavelength range 370 – 950 nm of main-sequence stars (G-M spectral type) within 100 pc.
Ph.D. Work
Hot stellar populations in Globular Clusters
My thesis work was based on studying the properties of hot stellar populations in Globular clusters (GCs) by combining AstroSat/UVIT with Gaia and HST observations. We mainly focused on constructing the UV-optical color-magnitude diagrams to understand the role of multiple stellar populations in the morphology of horizontal branch stars (NGC1851, NGC 288), radial distribution of blue straggler stars (BSSs), etc. We also studied the spectral energy distributions to derive the properties and identify hot companions to exotic objects such as BSSs (WD companion to a BSS in NGC 5466)
Stacked FUV-optical Color Magnitude diagrams of 11 GCs (Sahu et al. 2022)
To further expand our knowledge of GCs in UV, we carried out FUV legacy survey of GCs with UVIT (GlobULeS) with deep exposures (~10 Ksec) and provide a catalog in FUV with membership probabilities covering the entire cluster regions. Link to the full article.
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Refer to my publications on star clusters with AstroSat/UVIT on NASA ADS.
Press releases
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A star relives its youth while dancing with its wizened companion in NGC 5466, Astrosat Picture of the Month #018, March 2019.
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Hot Ultraviolet stars in the Globular Cluster NGC 288, Astrosat Picture of the Month #014, November 2018.
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NGC 1851: One cluster, two populations, Astrosat Picture of the Month #003, November 2017.