Research Topics - NASA/ADS

Multimessenger astronomy and astrophysics

I am a big fan of combining different methods and observing techniques to learn more about the Universe.

1. Pinpointing cosmic particle accelerators

Extragalactic neutrinos are among the most powerful messengers from the distant Universe, detectable even from regions opaque to light. My work focuses on uncovering their origin in radio-quiet and radio-loud AGN, such as Seyferts and blazars, respectively.

The IceCube Neutrino Observatory has detected hundreds of cosmic neutrinos between approximately 100 GeV and 10 PeV energies. The detector opens a new window into extreme astrophysical processes.

AGN host supermassive black holes that are efficient cosmic particle accelerators. I investigate these objects with multi-messenger tools including neutrino, gamma, hard X-ray and radio astronomy. I am member of the IceCube Collaboration since 2020.

Related publications:

• Zooming into the neutrino-associated blazar candidate J1718+4239 Perger et al. 2025, A&A 698, 2
• The nuclear jet and core of TXS 0506+056 could be gravitationally lensed Britzen et al. 2025, A&A 695, 103
• Possible correlation between unabsorbed hard x rays and neutrinos in radio-loud and radio-quiet active galactic nuclei Kun et al. 2024, PhRvD 110, 3014
• ICECUBE AGN neutrino candidate PKS 1717+177: dark deflector bends nuclear jet Britzen et al. 2024, MNRAS 535, 2742
• VLBI Analysis of a Potential High-Energy Neutrino Emitter Blazar Komives et al. 2024, Univ 10, 78
• Searching for temporary gamma-ray dark blazars associated with IceCube neutrinos Kun et al. 2023, A&A 679, 46
• Multiwavelength Analysis of the IceCube Neutrino Source Candidate Blazar PKS 1424+240 Kun and Medvezcky 2023, Symm 15, 270
• Neutrino Cadence of TXS 0506+056 Consistent with Supermassive Binary Origin Becker Tjus et al. 2022, ApJ Letters 941, 25
• Multimessenger Picture of J1048+7143 Kun et al. 2022, ApJ 940, 163
• Multiwavelength Search for the Origin of IceCube's Neutrinos Kun et al. 2022, ApJ 934, 180
• Cosmic Neutrinos from Temporarily Gamma-suppressed Blazars Kun et al. 2021, ApJ Letters 911, 18
• Very long baseline interferometry radio structure and radio brightening of the high-energy neutrino emitting blazar TXS 0506+056 Kun, Biermann, Gergely 2019, MNRAS Letters 483, 42
• On the High-Energy Neutrino Emission from Active Galactic Nuclei Kun, Biermann, Gergely, Britzen 2018, Univ 4, 24
• A flat-spectrum candidate for a track-type high-energy neutrino emission event, the case of blazar PKS 0723-008 Kun, Biermann, Gergely 2017, MNRAS Letters 466, 34
• Constraints on supermassive black hole spins from observations of active galaxy jets Kun et al. 2013, AN 334, 1024

2. Signatures of merging Supermassive Black Hole Binaries

Galaxy mergers can lead to the formation of binary supermassive black holes. If one or both of them are active, their jets may exhibit periodic structures, detectable via Very Long Baseline Interferometry (VLBI).

I analyze multi-epoch VLBI data of AGN jets to uncover jet kinematics and potential binary interactions, contributing to source identification for gravitational wave observatories.

Related publications:

• Follow-up on the Supermassive Black Hole Binary Candidate J1048+7143: Successful Prediction of the Next Gamma-Ray Flare and Refined Binary Parameters in the Framework of the Jet Precession Model Kun et al. 2024, ApJ 963, 16
• Signatures of a spinning supermassive black hole binary on the mas-scale jet of the quasar S5 1928+738 based on 25 yr of VLBI data Kun et al. 2023, MNRAS 526, 4698
• Precession-induced Variability in AGN Jets and OJ 287 Britzen et al. 2023, ApJ 951, 106
• From binary to singular: The AGN PSO J334.2028+1.4075 under the high-resolution scope Benke et al. 2023, A&A 677, 1
• Detection of a Peculiar Drift in the Nuclear Radio Jet of the TeV Blazar Markarian 501 Britzen et al. 2023, Univ 9, 115
• A self-lensing supermassive binary black hole at radio frequencies: the story of Spikey continues Kun, Frey & Gabanyi 2020, MNRAS 496, 3336
• Flaring radio lanterns along the ridge line: long-term oscillatory motion in the jet of S5 1803+784 Kun et al. 2018, MNRAS 478, 359
• Model simulation of jet precession in quasar PG 1302-102 Qian et al. 2018, A&A 615, 123
• A swirling jet in the quasar 1308+326 Britzen et al. 2017, A&A 602, 29
• Parsec-scale jet properties of the quasar PG 1302-102 Mohan et al. 2016, MNRAS 463, 1812
• Structure of the nucleus of 1928+738 Roland et al. 2015, A&A 578, 86
• Constraining the parameters of the putative supermassive binary black hole in PG 1302-102 from its radio structure Kun et al. 2015, MNRAS 454, 1290
• A spinning supermassive black hole binary model consistent with VLBI observations of the S5 1928+738 jet Kun et al. 2014, MNRAS 445, 1370

3. Cosmic radiation in old sediment layers

I also explore the effect of periodic exposure of the biosphere to increased cosmic radiation, leading to mutations in simple marine lifeforms.

4. Pulsar timing arrays

To detect the gravitational wave signal of individual sources above the stochastic background.

5. Galaxy rotation curves and dark matter models

I extensively studied the signatures of dark matter on galaxy rotation curves.

Related publications:

• Slowly rotating Bose-Einstein condensate compared with the rotation curves of 12 dwarf galaxies Kun, Keresztes, Gergely 2020, A&A 633, 75
• Dark Matter as a Non-Relativistic Bose-Einstein Condensate with Massive Gravitons Kun, Keresztes, Das, Gergely 2018, Symm 10, 520
• Comparative testing of dark matter models with 15 HSB and 15 LSB galaxies Kun, Keresztes, Simko, Szucs, Gergely 2017, A&A 608, 42