ZTF Faces

Nora Linn Stotjohann

Postdoctoral Fellow at the Weizmann Institute of Science, Israel

Your starting point and landing in the land of astronomy...

After growing up under the cloudy skies of Northern Germany by the Baltic coast, I studied physics at Bonn University. For my PhD thesis I moved to Berlin and became part of the IceCube group at Desy Zeuthen, where I searched for 100 second long neutrino bursts that could originate from short-lived sources such as GRBs, SNe with (choked) jets, or binary neutron star mergers. Part of my work was triggering and evaluating follow-up observations from optical, X-ray and gamma-ray telescopes to identify potential astrophysical neutrino sources.

What are you playing with in the ZTF playground?

After finishing my PhD thesis in October 2019, I joined the ZTF group at the Weizmann Institute of Science in Israel where I work most closely with Prof. Eran Ofek. Coming from a particle physics background, I especially like that the large amount of data collected by ZTF enables systematic searches. As a consequence, we are no longer dependent on chance discoveries, but can study large samples of objects to address specific scientific questions while accounting for biases and statistical fluctuations.

For my first ZTF project, I analyzed the pre-explosion light curves of 200 interacting supernovae which are known to exhibit major mass-loss events in the final years before the explosion. The 70,000 available pre-explosion images revealed that approximately 25% of the progenitor stars undergo months-long eruptions brighter than -13th magnitude immediately before their explosion as a supernova of Type IIn. Our intriguing results are now published in the Astrophysical Journal (Nora L. Strotjohann et al 2021 ApJ 907 99).

In addition to my work on supernova progenitors, I'm designing the guiding camera system for the LAST-spec telescope that will combine the light collected by 17 off-the-shelf telescopes in a single spectrograph. It will be part of the Weizmann Astronomical Observatory that is being built in a kibbutz in Southern Israel.

Where do you want to steer your rocket in the future?

Next, I plan to improve the sensitivity of the precursor search and extend it to core-collapse supernovae of all classes to measure how often their progenitor stars show similar outbursts. Thanks to the growing number of ZTF images and thousands of discovered supernovae, I will be able to detect outbursts that are 100-1000 times less frequent than the ones observed prior to Type IIn supernovae. The main challenge of this search will be analyzing several million of ZTF images while keeping the number of false detections low.

If you were not an astronomer, what would you be?

I would probably do research and data analysis in a different field. Outside of work, I enjoy trying new recipes, learning Hebrew, long hikes and dancing.

A book that shook your worldview?

I enjoy reading good books, but it takes much more to shake my world view.

If you’ve had a bad day at work, you will….

Compared to the Corona pandemic or other global crises, problems at work seem quite minor and easy to fix, so I didn't have many bad days because of work recently, also thanks to the support from my supervisors and colleagues. These days, I am grateful to live with my amazing flatmate and our cute and weird cat. I hope that it will soon become easier to visit my family in Germany.