Akshara Viswanathan
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astroakshara.bsky.social
Akshara Viswanathan
@astroakshara.bsky.social
230 followers 35 following 12 posts
PhD researcher in Kapteyn Institute, Groningen, NL| Observational astronomer investigating baby Milky Way's shenanigan |🇮🇳🇨🇦🇬🇧🇳🇱| she/her | தமிழச்சி
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So many emotions all at once!!! On December 6, I became a Doctor in Astrophysics and I am so very grateful to everyone who has been a part of this journey since the 11-year-old me wanted to get a PhD in 'astro-stuff'.
Here is a digital copy of my thesis: doi.org/10.33612/dis...
Reposted by Akshara Viswanathan
Paper day! Here is our attempt to summarize the exciting revolution Gaia has brought to the study of stellar streams around the Milky Way, as a part of a special issue of New Astronomy Reviews: arxiv.org/abs/2405.19410

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Celebrating Gaia's 10th birthday with some cake 😍 loved making the Milky Way map edible❤️✨ #ESAGaia
Thanks to my amazing co-authors @tada-matsuno.bsky.social @nfmartin1980.bsky.social @ankeaa.bsky.social and non-bluesky people - Else, Kim, Nicolas L., Raymond, Sebastien, Georges, Zhen, Martin, Federico.
Let me also take this chance to say that I'm on the postdoc market this fall. :)
You can grab the catalogue here: astroakshara.github.io/rvs-paper/Ga...
75% of these stars have either no/not reliable metallicity value in literature. This catalogue is also ideal to study the properties of VMP stars in different parts of our Galaxy. PS few VMPs are visible to the naked eye!
astroakshara.github.io
Now we have a catalogue of 1000 VMP stars all-sky that are so bright (G<13) ideal for high-res follow-up. This increases literature estimates by a factor of 3. It is incredible that I got to learn the power of archival data from big surveys to do science useful for the community
We also compare our metallicities to other works that analyse RVS spectra like the amazing GSP-Spec pipeline by the Gaia consortium and improvement in the VMP end by Matsuno+ 22. We have good agreement if used with their quality cuts, but this is only a small overlap (~25%)
We validate our inferred metallicities with existing spectroscopic surveys (APOGEE and GALAH) and dedicated high-resolution follow-up of VMP stars to learn the purity and precision of our analysis. Things look good, so the catalogue is good to go!
We utilize an MCMC pipeline to fit equivalent widths to all three Calcium Triplet lines i.e., 850.04 nm, 854.44 nm and 866.45 nm at the same time. We go from equivalent widths to metallicities using the Carrera+ 13 relation. It was cool to analyse spectra from the space!!
We use publicly available Gaia RVS spectra (of ~1 million sources) and pre-select potential VMP stars from photometric (or equivalent) metallicities from Pristine DR1 and Pristine Gaia-synthetic catalogues from Martin, Starkenburg+ 23 and Table 2 giants from Andrae+ 23.
Very happy to share my new paper on arxiv: arxiv.org/abs/2309.06137 releasing a catalogue of spectroscopic metallicities of VMP stars using the amazing Gaia DR3 RVS spectra. Did you know that there exists a lot of archival VMP spectra out there with no published parameters?
Gaia's brightest very metal-poor (VMP) stars: A metallicity...
Context. Gaia DR3 has offered the scientific community a remarkable dataset of approximately one million spectra acquired with the Radial Velocity Spectrometer (RVS) in the Calcium II triplet...
arxiv.org