The Astrophysical Journal Letters (Jan 2025)
The Kangaroo’s First Hop: The Early Fast Cooling Phase of EP250108a/SN 2025kg
- Rob A. J. Eyles-Ferris,
- Peter G. Jonker,
- Andrew J. Levan,
- Daniele Bjørn Malesani,
- Nikhil Sarin,
- Christopher L. Fryer,
- Jillian C. Rastinejad,
- Eric Burns,
- Nial R. Tanvir,
- Paul T. O’Brien,
- Wen-fai Fong,
- Ilya Mandel,
- Benjamin P. Gompertz,
- Charles D. Kilpatrick,
- Steven Bloemen,
- Joe S. Bright,
- Francesco Carotenuto,
- Gregory Corcoran,
- Laura Cotter,
- Paul J. Groot,
- Luca Izzo,
- Tanmoy Laskar,
- Antonio Martin-Carrillo,
- Jesse Palmerio,
- Maria E. Ravasio,
- Jan van Roestel,
- Andrea Saccardi,
- Rhaana L. C. Starling,
- Aishwarya Linesh Thakur,
- Susanna D. Vergani,
- Paul M. Vreeswijk,
- Franz E. Bauer,
- Sergio Campana,
- Jennifer A. Chacón,
- Ashley A. Chrimes,
- Stefano Covino,
- Joyce N. D. van Dalen,
- Valerio D’Elia,
- Massimiliano De Pasquale,
- Nusrin Habeeb,
- Dieter H. Hartmann,
- Agnes P. C. van Hoof,
- Páll Jakobsson,
- Yashaswi Julakanti,
- Giorgos Leloudas,
- Daniel Mata Sánchez,
- Christopher J. Nixon,
- Daniëlle L. A. Pieterse,
- Giovanna Pugliese,
- Jonathan Quirola-Vásquez,
- Ben C. Rayson,
- Ruben Salvaterra,
- Ben Schneider,
- Manuel A. P. Torres,
- Tayyaba Zafar
Affiliations
- Rob A. J. Eyles-Ferris
- ORCiD
- School of Physics and Astronomy, University of Leicester , University Road, Leicester LE1 7RH, UK ; [email protected]
- Peter G. Jonker
- ORCiD
- Department of Astrophysics/IMAPP, Radboud University , P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands
- Andrew J. Levan
- ORCiD
- Department of Astrophysics/IMAPP, Radboud University , P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands
- Daniele Bjørn Malesani
- ORCiD
- Cosmic Dawn Center (DAWN) , Denmark; Niels Bohr Institute, University of Copenhagen , Jagtvej 128, Copenhagen 2200, Denmark
- Nikhil Sarin
- ORCiD
- The Oskar Klein Centre, Department of Physics, Stockholm University , AlbaNova, Stockholm, SE-106 91 Stockholm, Sweden; Nordita, Stockholm University and KTH Royal Institute of Technology , Hannes Alfvéns väg 12, Stockholm, SE-106 91 Stockholm, Sweden
- Christopher L. Fryer
- ORCiD
- Center for Nonlinear Studies, Los Alamos National Laboratory , Los Alamos, NM 87545, USA
- Jillian C. Rastinejad
- ORCiD
- Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University , Evanston, IL 60208, USA
- Eric Burns
- ORCiD
- Department of Physics and Astronomy, Louisiana State University , Baton Rouge, LA 70803, USA
- Nial R. Tanvir
- ORCiD
- School of Physics and Astronomy, University of Leicester , University Road, Leicester LE1 7RH, UK ; [email protected]
- Paul T. O’Brien
- ORCiD
- School of Physics and Astronomy, University of Leicester , University Road, Leicester LE1 7RH, UK ; [email protected]
- Wen-fai Fong
- ORCiD
- Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University , Evanston, IL 60208, USA
- Ilya Mandel
- ORCiD
- School of Physics and Astronomy, Monash University , Clayton, VIC 3800, Australia; ARC Centre of Excellence for Gravitational-wave Discovery (OzGrav) , Melbourne, Australia
- Benjamin P. Gompertz
- ORCiD
- School of Physics and Astronomy, University of Birmingham , Birmingham B15 2TT, UK; Institute for Gravitational Wave Astronomy, University of Birmingham , Birmingham B15 2TT, UK
- Charles D. Kilpatrick
- ORCiD
- Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University , Evanston, IL 60208, USA
- Steven Bloemen
- ORCiD
- Department of Astrophysics/IMAPP, Radboud University , P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands
- Joe S. Bright
- ORCiD
- Astrophysics, Department of Physics, University of Oxford , Keble Road, Oxford OX1 3RH, UK
- Francesco Carotenuto
- ORCiD
- INAF-Osservatorio Astronomico di Roma , Via Frascati 33, I-00078 Monte Porzio Catone (RM), Italy
- Gregory Corcoran
- ORCiD
- School of Physics and Centre for Space Research, University College Dublin , Belfield, Dublin 4, Ireland
- Laura Cotter
- ORCiD
- School of Physics and Centre for Space Research, University College Dublin , Belfield, Dublin 4, Ireland
- Paul J. Groot
- ORCiD
- Department of Astrophysics/IMAPP, Radboud University , P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands; Department of Astronomy, University of Cape Town , Private Bag X3, Rondebosch 7701, South Africa; South African Astronomical Observatory , P.O. Box 9, Observatory 7935, South Africa
- Luca Izzo
- ORCiD
- Niels Bohr Institute, University of Copenhagen , Jagtvej 128, Copenhagen 2200, Denmark; Osservatorio Astronomico di Capodimonte , INAF, Salita Moiariello 16, Napoli, 80131, Italy
- Tanmoy Laskar
- ORCiD
- Department of Physics & Astronomy, University of Utah , Salt Lake City, UT 84112, USA; Department of Astrophysics/IMAPP, Radboud University , PO Box 9010, 6500 GL Nijmegen, The Netherlands
- Antonio Martin-Carrillo
- ORCiD
- School of Physics and Centre for Space Research, University College Dublin , Belfield, Dublin 4, Ireland
- Jesse Palmerio
- ORCiD
- Université Paris-Saclay , Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
- Maria E. Ravasio
- ORCiD
- Department of Astrophysics/IMAPP, Radboud University , P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands; INAF—Osservatorio Astronomico di Brera , Via E. Bianchi 46, I-23807 Merate, (LC), Italy
- Jan van Roestel
- ORCiD
- Anton Pannekoek Institute for Astronomy, University of Amsterdam , 1090 GE Amsterdam, The Netherlands
- Andrea Saccardi
- ORCiD
- Université Paris-Saclay , Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
- Rhaana L. C. Starling
- ORCiD
- School of Physics and Astronomy, University of Leicester , University Road, Leicester LE1 7RH, UK ; [email protected]
- Aishwarya Linesh Thakur
- ORCiD
- INAF—Istituto di Astrofisica e Planetologia Spaziali , Via Fosso del Cavaliere 100, 00133 Roma, Italy
- Susanna D. Vergani
- ORCiD
- INAF—Osservatorio Astronomico di Brera , Via E. Bianchi 46, I-23807 Merate, (LC), Italy; GEPI, Observatoire de Paris, Université PSL , CNRS, 5 Pace Jules Janssen, F-92190 Meudon, France
- Paul M. Vreeswijk
- Department of Astrophysics/IMAPP, Radboud University , P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands
- Franz E. Bauer
- ORCiD
- Instituto de Alta Investigación, Universidad de Tarapacá , Casilla 7D, Arica, Chile
- Sergio Campana
- ORCiD
- INAF—Osservatorio Astronomico di Brera , Via E. Bianchi 46, I-23807 Merate, (LC), Italy
- Jennifer A. Chacón
- ORCiD
- Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile , Campus San Joaquín, Av. Vicuña Mackenna 4860, Macul Santiago 7820436, Chile; Millennium Institute of Astrophysics , Nuncio Monseñor Sótero Sanz 100, 104 Providencia, Santiago, Chile
- Ashley A. Chrimes
- ORCiD
- Department of Astrophysics/IMAPP, Radboud University , P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands; European Space Agency (ESA) , European Space Research and Technology Centre (ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
- Stefano Covino
- ORCiD
- INAF—Osservatorio Astronomico di Brera , Via E. Bianchi 46, I-23807 Merate, (LC), Italy; Como Lake Centre for AstroPhysics (CLAP), DiSAT, Universitá dell’Insubria , Via Valleggio 11, 22100 Como, Italy
- Joyce N. D. van Dalen
- ORCiD
- Department of Astrophysics/IMAPP, Radboud University , P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands
- Valerio D’Elia
- ORCiD
- Space Science Data Center (SSDC)—Agenzia Spaziale Italiana (ASI) , I-00133 Roma, Italy
- Massimiliano De Pasquale
- ORCiD
- Department of Mathematics and Computer Sciences, Physical Sciences and Earth Sciences, University of Messina , Via F. S. D’Alcontres 31, 98166 Messina, Italy
- Nusrin Habeeb
- ORCiD
- School of Physics and Astronomy, University of Leicester , University Road, Leicester LE1 7RH, UK ; [email protected]
- Dieter H. Hartmann
- ORCiD
- Department of Physics and Astronomy, Clemson University , Clemson, SC 29634-0978, USA
- Agnes P. C. van Hoof
- ORCiD
- Department of Astrophysics/IMAPP, Radboud University , P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands
- Páll Jakobsson
- ORCiD
- Center for Astrophysics and Cosmology, Science Institute, University of Iceland , Dunhagi 5, 107 Reykijavík, Iceland
- Yashaswi Julakanti
- ORCiD
- School of Physics and Astronomy, University of Leicester , University Road, Leicester LE1 7RH, UK ; [email protected]
- Giorgos Leloudas
- ORCiD
- DTU Space, National Space Institute, Technical University of Denmark , Elektrovej 327, 2800 Kgs. Lyngby, Denmark
- Daniel Mata Sánchez
- ORCiD
- Instituto de Astrofísica de Canarias , E-38205 La Laguna, Tenerife, Spain; Departamento de Astrofísica, University de La Laguna , E-38206 La Laguna, Tenerife, Spain
- Christopher J. Nixon
- ORCiD
- School of Physics and Astronomy, Sir William Henry Bragg Building, University of Leeds , Woodhouse Ln., Leeds LS2 9JT, UK
- Daniëlle L. A. Pieterse
- ORCiD
- Department of Astrophysics/IMAPP, Radboud University , P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands
- Giovanna Pugliese
- ORCiD
- Astronomical Institute Anton Pannekoek, University of Amsterdam , 1090 GE Amsterdam, The Netherlands
- Jonathan Quirola-Vásquez
- ORCiD
- Department of Astrophysics/IMAPP, Radboud University , P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands
- Ben C. Rayson
- ORCiD
- School of Physics and Astronomy, University of Leicester , University Road, Leicester LE1 7RH, UK ; [email protected]
- Ruben Salvaterra
- ORCiD
- INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano , Via A. Corti 12, 20133 Milano, Italy
- Ben Schneider
- ORCiD
- Aix Marseille University , CNRS, CNES, LAM, Marseille, France
- Manuel A. P. Torres
- ORCiD
- Instituto de Astrofísica de Canarias , E-38205 La Laguna, Tenerife, Spain; Departamento de Astrofísica, University de La Laguna , E-38206 La Laguna, Tenerife, Spain
- Tayyaba Zafar
- ORCiD
- School of Mathematical and Physical Sciences, Macquarie University , NSW 2109, Australia
- DOI
- https://doi.org/10.3847/2041-8213/ade1d9
- Journal volume & issue
-
Vol. 988,
no. 1
p. L14
Abstract
Fast X-ray transients 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 expansionof 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 Letter 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 6 days, including our measurement of the redshift of z = 0.17641. We compare to other supernovae and fast transients showing similar features, finding significant similarities with SN 2006aj and SN 2020bvc, and show 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 (≲10 ^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 a trapped jet. This makes SN 2025 one of the few examples of this currently observationally rare event.
Keywords
