The picture shows Vishaak standing in the library of the Hamburg observatory, next to his final slide of his progress report
He just gave his progress report and will finish his MSc thesis later this year. So, now the best part, if you are looking for an amazing PhD student who knows binary evolution, large spectroscopic surveys, transients etc. he is still looking for a PhD position.
Once in outburst he submits the object to SDSS-V for identification, with the goal to find a rare helium CV - a so called AM CVn binary. Although, so far all observed objects are regular hydrogen-rich CVs, he is testing the capabilities of this new ToO mode and provides lots of interesting feedback
@sdssurveys.bsky.social is pioneering ToO observations with a large scale multi-object spectroscopic survey. For the first time we use a MOS survey to identify transients. My MSc student, Vishaak Balasubramanya, is monitoring >10,000 accreting white dwarfs with ZTF and in the future LSST
"The supernova Ia progenitor problem in the 2040s"
ui.adsabs.harvard.edu/abs/2025arXi...
"The final stages of binary evolution using multi-messenger studies"
ui.adsabs.harvard.edu/abs/2025arXi...
🔭
If you are interested, we submitted white papers about this topic to the recent call of white papers from @eso.org to address the question "What science questions will astronomy need to answer in the 2040s" which is part of their Expanding horizons program 🔭
Well, what you need is one or more arrays of small to medium-size telescopes which can take spectra with no readout penalty independently from each other or combined as a large array acting as single telescope. 🔭
How can we best observe the most compact binaries with orbital periods as short as a few minutes, close to their final merger? They are strong supernova Ia progenitor candidates crucial to cosmology and are the strongest Galactic gravitational wave sources in the @lisacommunity.bsky.social regime 🔭
This was a very successful study making use of high quality HST UV spectra and is only the first in a series of several. HST has observed a dozen AMCVns which will give us enough statistics to solve the puzzle what are the donor stars in AMCVns. Stay tuned for more exciting work from Will. (7/7) 🔭
We also found a higher accretor temperature than previous studies and a rather massive accreting white dwarf. If that holds for other systems that means that their gravitational wave signal will be stronger than previously thought with more typical white dwarf masses. (6/7) 🔭
Most importantly, we found a strong enhancement of nitrogen, which points to CNO processed material in the donor which is currently being transferred to the accretor. This points to either a white dwarf donor or a system that has evolved from a regular CV; we can exclude a He-star donor (5/7) 🔭
That is exactly what Will has done. We took UV spectra with the Hubble Space telescope (HST) of this benchmark AMCVn to study the spectral features, measures abundances and properties of the accreting white dwarf. We found features of elements such as nitrogen, silicon, iron, or aluminium (4/7) 🔭
Despite their importance, we have no idea what the donors are, besides that they are helium rich. The accreting white dwarf and accretion disc outshine the donor. So we have to use a trick and observe the material that has been transferred to the accreting white dwarf from the donor. (3/7) 🔭
AMCVn binaries are ultracompact accreting white dwarfs which are important as supernova Ia progenitors, @lisacommunity.bsky.social gravitational wave sources and mark the end point of binary evolution.They are extreme in many ways and can reach orbital periods as short as 5min (2/7) 🔭
Congratulations to my PhD student Weitian (Will) Yu @uni-hamburg.de for his first 1st author paper: arxiv.org/pdf/2512.04147 He did the first detailed abundance analysis of an ultracompact AMCVn binary ZTFJ2252-0519. What did we learn from this analysis (1/7) 🔭
A big thank you also to Martin M. Roth for giving us a quick tour of the Zentrum für Technologieentwicklung (ZTE). I can only say: Very impressive! @uni-hamburg.de
The conference was held in the Synagogue Kulturzentrum; one of the most beautiful buildings I had ever given a presentation. Deutsches Zentrum für Astrophysik congratulations to a great conference!
I had so much fun presenting our @eso.org Expanding horizons idea for the Time Domain Telescope and its connection to multi-messenger astrophysics at the @germanastrosoc.bsky.social meeting organized by the Deutsches Zentrum für Astrophysik in the really pretty town Görlitz. 🔭🧪
Thanks a lot for organizing a great town hall about the different ideas for the ESO Expanding horizons program 🔭
We also had the opportunity to spend some fun hours together and even show the team parts of the beautiful city of Hamburg @uni-hamburg.de
This week we welcomed the BlackGEM collaboration for a team meeting at Hamburg Observatory. We had lots of exciting science presentations and many fruitful conversations about the amazing science we already have been doing with BlackGEM and will be doing in the future.
We also had to say goodbye to two amazing RISE students, Bennett Kirby and Isabel Jackson, who spend the summer in Hamburg working with us on radial mode pulsators and supernova Ia progenitors @uni-hamburg.de
Group picture of the research group of Prof. Kupfer in front of the main building at Hamburg Observatory
Three weeks ago my close collaborator and friend Brad N. Barlow came to visit us at the observatory with one of his graduate students. We had a great collaboration meeting with lots of inspiring discussions!
Picture shows the front of the Max Planck Institute of Astrophysics
Looking Forward to great 3 day visit at @maxplanck.de for Astrophysics to give the Joint Astro Colloquium.
The picture shows the presenter giving the talk in the historic library at Hamburg observatory
Today, we had a very inspiring Colloquium on the incredible things we will be able to do with @lisacommunity.bsky.social Valeriya certainly sparked lots of interest about the mission here at Hamburg observatory
I am looking for a PhD student to join us at Hamburg observatory to work on compact binaries, LISA sources and supernova Ia progenitors. The position is funded through my ERC starting grant. Application deadline is February 28th and you can apply follow the link:
www.uni-hamburg.de/stellenangeb...
I'm a Professor of Astronomy at the university of Hamburg. I work on compact binaries, LISA sources, Supernova progenitors and large scale surveys.
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