Hello, I am

Viraj Karambelkar


An Astronomer in New York City.
vk2588 [at] columbia.edu

About me

I am a NASA Hubble Fellow at Columbia University. I finished my PhD from the Astrophysics Department at Caltech in 2025. I received my Bachelors degree from the Indian Institute of Technology Bombay in 2019.
My work focuses on the study of our dynamic sky. I study unusual cosmic explosions, stars that show unusual brightness variations and hunt for light accompanying gravitational waves.

I use robotic telescopes that survey the sky, preferably at infrared wavelengths, to look for such stars and explosions.
Viraj Karambelkar

My publications

Here is a complete list of my refereed publications, and here is a list of publications where I am the first-author or have major contributions.

Media / Outreach

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Astrobites

I was an astrobites author for two years! Check out my articles here.
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Star eats planet!

Our paper on a star engulfing a planet made it to the NY Times cover!
Some more articles featuring me here and here.
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Dimmest supernova ever!

A New Scientist article featuring me talking about the dimmest supernova discovered to date.
A Youtube video of me talking about this supernova.
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Mentorship

So far, I have mentored three awesome undergraduate students - Kayton Truong (2021), Sulekha Kishore (2022) and Aswin Suresh (2023) for summer research projects as part of the Caltech Summer Undergrad Research Fellowship program.
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Astronomy Public Outreach

I enjoy volunteering at astronomy outreach events in and around Pasadena. My favorites include Astronomy on Tap, curbside stargazing sessions, public lectures and stargazing nights at Caltech.

Research Description

I use survey telescopes across the world and in space, such as WINTER, NEOWISE, SPHEREx, PGIR, ZTF. I have worked on the following scientific areas:-

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Stellar Mergers and Common-Envelope Evolution
I am currently most focused on understanding transients from common-envelope evolution. Luminous Red Novae (LRNe) are transients associated with the final stages of common-envelope evolution in stellar binaries - a stellar merger or common-envelope ejection. LRNe have low intrinsic luminosities, making them observationally rare. I study these transients using ZTF, WINTER, NEOWISE, and JWST.
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Electromagnetic followup of gravitational waves
I work with ZTF and WINTER teams to follow-up gravitational wave alerts detected by the LIGO collaboration to search for their electromagnetic counterparts - the elusive kilonovae.
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Dusty Variable stars
Using PGIR and more recently SPHEREx, I search for dusty variable stars in the Milky Way. This includes dusty AGB stars, R Coronae Borealis stars, symbiotic binaries, carbon stars, and young stellar objects.
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Unusual low luminosity explosions


I am interested in odd-ball, subluminous explosions, such as low luminosity Type Iax supernovae and Intermediate luminosity red transients. I use ZTF, WINTER and JWST to study these explosions.

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Data processing pipelines for time-domain surveys


I co-created mirar (Modular Image Reduction and Analysis Resource) - an open-source python package for processing and analyzing images from time-domain surveys. The modular and flexible design of mirar allows for reducing images and detecting transients by performing image subtraction on images from any optical/infrared telescope. Originally built to process WINTER data, mirar is now being used to process data from four other telescopes.