1. SN 2023tsz : a helium-interaction-driven supernova in a very low-mass galaxyB. Warwick, J. Lyman, M. Pursiainen, Deanne L. Coppejans, L. Galbany, Gareth T. Jones, T. L. Killestein, A. Kumar, S. R. Oates, Tanja Petrushevska, 2025, original scientific article Keywords: circumstellar matter, stars, transients, supernovae
Published in RUNG: 20.01.2025; Views: 463; Downloads: 5
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4. Multiwavelength observations of the extraordinary accretion event AT2021lwxP. Wiseman, Y. Wang, S. Hönig, N. Castro-Segura, P. Clark, C. Frohmaier, M. D. Fulton, Giorgos Leloudas, M. D. Fulton, Tanja Petrushevska, 2023, original scientific article Keywords: accretion, accretion discs, tidal disruption events, transients, galaxies, supermassive black holesc
Published in RUNG: 15.05.2023; Views: 2432; Downloads: 5
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5. The rise and fall of the iron-strong nuclear transient PS16dtmTanja Petrushevska, Giorgos Leloudas, D. Ilić, Mateusz Bronikowski, P. Charalampopoulos, G. K. Jaisawal, E. Paraskeva, M. Pursiainen, Andreja Gomboc, Barbara Marčun, 2023, original scientific article Abstract: Context. Thanks to the advent of large-scale optical surveys, a diverse set of flares from the nuclear regions of galaxies has recently been discovered. These include the disruption of stars by supermassive black holes at the centers of galaxies – nuclear transients known as tidal disruption events (TDEs). Active galactic nuclei (AGN) can show extreme changes in the brightness and emission line intensities, often referred to as changing-look AGN (CLAGN). Given the physical and observational similarities, the interpretation and distinction of nuclear transients as CLAGN or TDEs remains difficult. One of the obstacles of making progress in the field is the lack of well-sampled data of long-lived nuclear outbursts in AGN.
Aims. Here, we study PS16dtm, a nuclear transient in a Narrow Line Seyfert 1 (NLSy1) galaxy, which has been proposed to be a TDE candidate. Our aim is to study the spectroscopic and photometric properties of PS16dtm, in order to better understand the outbursts originating in NLSy1 galaxies.
Methods. Our extensive multiwavelength follow-up that spans around 2000 days includes photometry and spectroscopy in the UV/optical, as well as mid-infrared (MIR) and X-ray observations. Furthermore, we improved an existing semiempirical model in order to reproduce the spectra and study the evolution of the spectral lines.
Results. The UV/optical light curve shows a double peak at ∼50 and ∼100 days after the first detection, and it declines and flattens afterward, reaching preoutburst levels after 2000 days of monitoring. The MIR light curve rises almost simultaneously with the optical, but unlike the UV/optical which is approaching the preoutburst levels in the last epochs of our observations, the MIR emission is still rising at the time of writing. The optical spectra show broad Balmer features and the strongest broad Fe II emission ever detected in a nuclear transient. This broad Fe II emission was not present in the archival preoutburst spectrum and almost completely disappeared +1868 days after the outburst. We found that the majority of the flux of the broad Balmer and Fe II lines is produced by photoionization. We detect only weak X-ray emission in the 0.5−8 keV band at the location of PS16dtm, at +848, +1130, and +1429 days past the outburst. This means that the X-ray emission continues to be lower by at least an order of magnitude, compared to archival, preoutburst measurements.
Conclusions. We confirm that the observed properties of PS16dtm are difficult to reconcile with normal AGN variability. The TDE scenario continues to be a plausible explanation for the observed properties, even though PS16dtm shows differences compared to TDE in quiescent galaxies. We suggest that this event is part of a growing sample of TDEs that show broad Balmer line profiles and Fe II complexes. We argue that the extreme variability seen in the AGN host due to PS16dtm may have easily been misclassified as a CLAGN, especially if the rising part of the light curve had been missed. This implies that some changing look episodes in AGN may be triggered by TDEs. Imaging and spectroscopic data of AGN with good sampling are needed to enable testing of possible physical mechanisms behind the extreme variability in AGN.
Keywords: nuclear transients, supermassive black holes, tidal disruption events, active galactic nuclei
Published in RUNG: 24.01.2023; Views: 3335; Downloads: 25
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6. Searches for Ultra-High-Energy Photons at the Pierre Auger ObservatoryP. Abreu, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, review article Abstract: The Pierre Auger Observatory, being the largest air-shower experiment in the world, offers an unprecedented exposure to neutral particles at the highest energies. Since the start of data taking more than 18 years ago, various searches for ultra-high-energy (UHE, E > 10[sup]17 eV) photons have been performed: either for a diffuse flux of UHE photons, for point sources of UHE photons or for UHE photons associated with
transient events like gravitational wave events. In the present paper, we summarize these searches and review
the current results obtained using the wealth of data collected by the Pierre Auger Observatory.
Keywords: photons, ultra-high energies, air showers, Pierre Auger Observatory, upper limits, transients
Published in RUNG: 03.01.2023; Views: 2962; Downloads: 0
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7. The rise and fall of the iron-strong nuclear transient PS16dtmTanja Petrushevska, 2022, published scientific conference contribution abstract Abstract: Thanks to the advent of large-scale optical surveys, a diverse set of flares from the nuclear regions of galaxies has recently been discovered. These include the disruption of stars by supermassive black holes at the centres of galaxies - nuclear transients known as tidal disruption events (TDEs). Active galactic nuclei (AGN) can show extreme changes in the brightness and emission line intensities, often referred to as changing-look AGN (CLAGN). Given the physical and observational similarities, the interpretation and distinction of nuclear transients as CLAGN or TDEs remains difficult. One of the obstacles of making progress in the field is the lack of well-sampled data of long-lived nuclear outbursts in AGN. I will present PS16dtm, a nuclear transient in a Narrow Line Seyfert 1 (NLSy1) galaxy which has been proposed to be a TDE candidate. I will show our multi-year spectroscopic and photometric study of PS16dtm, which can help us to better understand the outbursts originating in NLSy1 galaxies.
Keywords: supermassive black holes, active galactic nuclei, transients
Published in RUNG: 09.11.2022; Views: 2266; Downloads: 11
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8. Gaia Early Data Release 3 : Gaia photometric science alertsSimon Hodgkin, D. L. Harrison, E. Breedt, T. Wevers, Guy Rixon, A. Delgado, A. Yoldas, Z. Kostrzewa-Rutkowska, Mitja Fridman, Andreja Gomboc, 2021, original scientific article Keywords: Gaia satellite, transients, alerts
Published in RUNG: 02.11.2021; Views: 2828; Downloads: 10
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