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| Formato: | Preprint |
| Publicado: |
2025
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| Materias: | |
| Acceso en línea: | https://arxiv.org/abs/2504.08886 |
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| author | Eyles-Ferris, Rob A. J. Jonker, Peter G. Levan, Andrew J. Malesani, Daniele Bjørn Sarin, Nikhil Fryer, Christopher L. Rastinejad, Jillian C. Burns, Eric Tanvir, Nial R. O'Brien, Paul T. Fong, Wen-fai Mandel, Ilya Gompertz, Benjamin P. Kilpatrick, Charles D. Bloemen, Steven Bright, Joe S. Carotenuto, Francesco Corcoran, Gregory Cotter, Laura Groot, Paul J. Izzo, Luca Laskar, Tanmoy Martin-Carrillo, Antonio Palmerio, Jesse Ravasio, Maria E. van Roestel, Jan Saccardi, Andrea Starling, Rhaana L. C. Thakur, Aishwarya Linesh Vergani, Susanna D. Vreeswijk, Paul M. Bauer, Franz E. Campana, Sergio Chacón, Jennifer A. Chrimes, Ashley A. Covino, Stefano van Dalen, Joyce N. D. D'Elia, Valerio De Pasquale, Massimiliano Habeeb, Nusrin Hartmann, Dieter H. van Hoof, Agnes P. C. Jakobsson, Páll Julakanti, Yashaswi Leloudas, Giorgos Sánchez, Daniel Mata Nixon, Christopher J. Pieterse, Daniëlle L. A. Pugliese, Giavanna Quirola-Vásquez, Jonathan Rayson, Ben C. Salvaterra, Ruben Schneider, Ben Torres, Manuel A. P. Zafar, Tayyaba |
| author_facet | Eyles-Ferris, Rob A. J. Jonker, Peter G. Levan, Andrew J. Malesani, Daniele Bjørn Sarin, Nikhil Fryer, Christopher L. Rastinejad, Jillian C. Burns, Eric Tanvir, Nial R. O'Brien, Paul T. Fong, Wen-fai Mandel, Ilya Gompertz, Benjamin P. Kilpatrick, Charles D. Bloemen, Steven Bright, Joe S. Carotenuto, Francesco Corcoran, Gregory Cotter, Laura Groot, Paul J. Izzo, Luca Laskar, Tanmoy Martin-Carrillo, Antonio Palmerio, Jesse Ravasio, Maria E. van Roestel, Jan Saccardi, Andrea Starling, Rhaana L. C. Thakur, Aishwarya Linesh Vergani, Susanna D. Vreeswijk, Paul M. Bauer, Franz E. Campana, Sergio Chacón, Jennifer A. Chrimes, Ashley A. Covino, Stefano van Dalen, Joyce N. D. D'Elia, Valerio De Pasquale, Massimiliano Habeeb, Nusrin Hartmann, Dieter H. van Hoof, Agnes P. C. Jakobsson, Páll Julakanti, Yashaswi Leloudas, Giorgos Sánchez, Daniel Mata Nixon, Christopher J. Pieterse, Daniëlle L. A. Pugliese, Giavanna Quirola-Vásquez, Jonathan Rayson, Ben C. Salvaterra, Ruben Schneider, Ben Torres, Manuel A. P. Zafar, Tayyaba |
| contents | Fast X-ray transients (FXTs) are a rare and poorly understood population of events. Previously difficult to detect in real time, the launch of the Einstein Probe with its wide field X-ray telescope has led to a rapid expansion in the sample and allowed the exploration of these transients across the electromagnetic spectrum. EP250108a is a recently detected example linked to an optical counterpart, SN 2025kg, or 'the kangaroo'. Together with a companion paper (Rastinejad et al. 2025), we present our observing campaign and analysis of this event. In this letter, we focus on the early evolution of the optical counterpart over the first six days, including our measurement of the redshift of $z=0.17641$. We find that the source is well-modelled by a rapidly expanding cooling blackbody. We show the observed X-ray and radio properties are consistent with a collapsar-powered jet that is low energy ($\lesssim10^{51}$ erg) and/or fails to break out of the dense material surrounding it. While we examine the possibility that the optical emission emerges from the shock produced as the supernova ejecta expand into a dense shell of circumstellar material, due to our X-ray and radio inferences, we favour a model where it arises from a shocked cocoon resulting from the trapped jet. This makes SN 2025kg one of the few examples of this currently observationally rare event. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2504_08886 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The kangaroo's first hop: the early fast cooling phase of EP250108a/SN 2025kg Eyles-Ferris, Rob A. J. Jonker, Peter G. Levan, Andrew J. Malesani, Daniele Bjørn Sarin, Nikhil Fryer, Christopher L. Rastinejad, Jillian C. Burns, Eric Tanvir, Nial R. O'Brien, Paul T. Fong, Wen-fai Mandel, Ilya Gompertz, Benjamin P. Kilpatrick, Charles D. Bloemen, Steven Bright, Joe S. Carotenuto, Francesco Corcoran, Gregory Cotter, Laura Groot, Paul J. Izzo, Luca Laskar, Tanmoy Martin-Carrillo, Antonio Palmerio, Jesse Ravasio, Maria E. van Roestel, Jan Saccardi, Andrea Starling, Rhaana L. C. Thakur, Aishwarya Linesh Vergani, Susanna D. Vreeswijk, Paul M. Bauer, Franz E. Campana, Sergio Chacón, Jennifer A. Chrimes, Ashley A. Covino, Stefano van Dalen, Joyce N. D. D'Elia, Valerio De Pasquale, Massimiliano Habeeb, Nusrin Hartmann, Dieter H. van Hoof, Agnes P. C. Jakobsson, Páll Julakanti, Yashaswi Leloudas, Giorgos Sánchez, Daniel Mata Nixon, Christopher J. Pieterse, Daniëlle L. A. Pugliese, Giavanna Quirola-Vásquez, Jonathan Rayson, Ben C. Salvaterra, Ruben Schneider, Ben Torres, Manuel A. P. Zafar, Tayyaba High Energy Astrophysical Phenomena Fast X-ray transients (FXTs) are a rare and poorly understood population of events. Previously difficult to detect in real time, the launch of the Einstein Probe with its wide field X-ray telescope has led to a rapid expansion in the sample and allowed the exploration of these transients across the electromagnetic spectrum. EP250108a is a recently detected example linked to an optical counterpart, SN 2025kg, or 'the kangaroo'. Together with a companion paper (Rastinejad et al. 2025), we present our observing campaign and analysis of this event. In this letter, we focus on the early evolution of the optical counterpart over the first six days, including our measurement of the redshift of $z=0.17641$. We find that the source is well-modelled by a rapidly expanding cooling blackbody. We show the observed X-ray and radio properties are consistent with a collapsar-powered jet that is low energy ($\lesssim10^{51}$ erg) and/or fails to break out of the dense material surrounding it. While we examine the possibility that the optical emission emerges from the shock produced as the supernova ejecta expand into a dense shell of circumstellar material, due to our X-ray and radio inferences, we favour a model where it arises from a shocked cocoon resulting from the trapped jet. This makes SN 2025kg one of the few examples of this currently observationally rare event. |
| title | The kangaroo's first hop: the early fast cooling phase of EP250108a/SN 2025kg |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2504.08886 |