Géza Csörnyei

Observational astronomer working on supernovae, Cepheids, and independent distance indicators, with a broader interest in the extragalactic distance scale and the Hubble tension.

I completed both my bachelor’s and master’s studies at Eötvös Loránd University in Budapest, alongside work at Konkoly Observatory. I then joined the Max Planck Institute for Astrophysics in Garching through the International Max Planck Research School (IMPRS), received my PhD in April 2024, and am currently based at the European Southern Observatory as an ESO Fellow.

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Research interests: supernova spectroscopy, Cepheids, distance indicators, and the local distance scale.

Research

My work spans several areas of observational astrophysics, with a particular focus on supernovae, Cepheids, and the extragalactic distance scale.

• Cepheids. Investigation of Classical Cepheids, including period changes and variability, in collaboration with the Seismolab group at Konkoly Observatory and the H1PStars group at EPFL.
• Extragalactic spectroscopy. Study of emission lines in star-forming and AGN galaxies, with applications to photometric redshift estimation and galaxy classification using SDSS data.
• Type II supernovae. Spectral modelling of Type II supernovae using the TARDIS radiative transfer code, with the aim of deriving distances and testing systematic uncertainties.
• Distance scale and the Hubble tension. Cross-comparison of independent distance indicators, including Cepheids, TRGB, J-AGB, and Type II supernovae, to investigate systematic effects and the origin of the Hubble tension.

Selected Publications

A selection of first-author publications with brief summaries. Click on each title or image to read more, or use the buttons for the full record and article.

ADS libraries

• Refereed works (ADS)
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You can use these ADS libraries as the primary up-to-date record of my publications.

Featured paper

Clarifying the distance to M 51 based on Cepheids and a Type IIP supernova

M 51 is one of the best-known nearby galaxies, yet its distance has long remained uncertain. This work established a Cepheid-based distance and compared it with constraints from spectral modeling of a Type IIP supernova in the same host.

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Between Plateaus and Slopes: spectral diversity across Type IIP/L supernovae

This paper explores whether Type IIP and IIL supernovae form distinct subclasses or a continuum. Using a data-driven analysis of spectral time series, we showed that indeed a continuum exists, but both hydrogen-envelope mass differences and circumstellar-material interaction are necessary to understand the diversity.

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Consistency of Type IIP supernova sibling distances

This study tested the internal consistency of Type IIP supernova distance estimates by applying spectral modeling based method to events that exploded in the same galaxy, providing a direct check on precision and possible systematics.

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Period changes of Galactic Classical Cepheids

Using a large sample of Galactic Cepheids, this work explored period evolution and further showed that these stars are not perfectly regular clocks: in addition to secular evolution, they also exhibit detectable fluctuations.

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Emission lines and photometric redshifts

This project examined how realistic emission-line behaviour affects photometric redshift estimates. The results showed that emission lines, though highly variable, can substantially improve redshift accuracy.

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Revisiting AU Pegasi

This paper revisited the peculiar Type II Cepheid AU Pegasi, focusing on its strong period changes and on how new observations refine the picture that had emerged from earlier studies.

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Teaching

Teaching material and course resources.