The Radio Counterpart to the Fast X-Ray Transient EP240414a
Despite being operational for only a short time, the Einstein Probe mission, with its large field of view and rapid localization capabilities, has already significantly advanced the study of rapid variability in the soft X-ray sky. We report the discovery of luminous and variable radio emission from...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/adaaef |
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| author | Joe S. Bright Francesco Carotenuto Rob Fender Carmen Choza Andrew Mummery Peter G. Jonker Stephen J. Smartt David R. DeBoer Wael Farah James Matthews Alexander W. Pollak Lauren Rhodes Andrew Siemion |
| author_facet | Joe S. Bright Francesco Carotenuto Rob Fender Carmen Choza Andrew Mummery Peter G. Jonker Stephen J. Smartt David R. DeBoer Wael Farah James Matthews Alexander W. Pollak Lauren Rhodes Andrew Siemion |
| author_sort | Joe S. Bright |
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| description | Despite being operational for only a short time, the Einstein Probe mission, with its large field of view and rapid localization capabilities, has already significantly advanced the study of rapid variability in the soft X-ray sky. We report the discovery of luminous and variable radio emission from the Einstein Probe fast X-ray transient EP240414a, the second such source with a radio counterpart. The radio emission at 3 GHz peaks at ∼30 days postexplosion and with a spectral luminosity ∼2 × 10 ^30 erg s ^−1 Hz ^−1 , similar to what is seen from long gamma-ray bursts, and distinct from other extragalactic transients including supernovae and tidal disruption events, although we cannot completely rule out emission from engine driven stellar explosions, e.g., the fast blue optical transients. An equipartition analysis of our radio data reveals that an outflow with at least a moderate bulk Lorentz factor (Γ ≳ 1.6) with a minimum energy of ∼10 ^48 erg is required to explain our observations. The apparent lack of a reported gamma-ray counterpart to EP240414a could suggest that an off-axis or choked jet could be responsible for the radio emission, although a low-luminosity gamma-ray burst may have gone undetected. Our observations are consistent with the hypothesis that a significant fraction of extragalactic fast X-ray transients are associated with the deaths of massive stars. |
| format | Article |
| id | doaj-art-1665c73e3d79422dba7d0963a4e6f6e2 |
| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-1665c73e3d79422dba7d0963a4e6f6e22025-08-20T02:15:37ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198114810.3847/1538-4357/adaaefThe Radio Counterpart to the Fast X-Ray Transient EP240414aJoe S. Bright0https://orcid.org/0000-0002-7735-5796Francesco Carotenuto1https://orcid.org/0000-0002-0426-3276Rob Fender2Carmen Choza3https://orcid.org/0009-0008-0662-1293Andrew Mummery4Peter G. Jonker5https://orcid.org/0000-0001-5679-0695Stephen J. Smartt6https://orcid.org/0000-0002-8229-1731David R. DeBoer7https://orcid.org/0000-0003-3197-2294Wael Farah8https://orcid.org/0000-0002-0161-7243James Matthews9https://orcid.org/0000-0002-3493-7737Alexander W. Pollak10https://orcid.org/0000-0002-3430-7671Lauren Rhodes11https://orcid.org/0000-0003-2705-4941Andrew Siemion12https://orcid.org/0000-0003-2828-7720Astrophysics, Department of Physics, The University of Oxford , Keble Road, Oxford OX1 3RH, UK ; joe.bright@physics.ox.ac.uk; Breakthrough Listen, Astrophysics, Department of Physics, The University of Oxford , Keble Road, Oxford OX1 3RH, UKAstrophysics, Department of Physics, The University of Oxford , Keble Road, Oxford OX1 3RH, UK ; joe.bright@physics.ox.ac.ukAstrophysics, Department of Physics, The University of Oxford , Keble Road, Oxford OX1 3RH, UK ; joe.bright@physics.ox.ac.uk; Department of Astronomy , University of Cape Town, Private Bag X3, Rondebosch 7701, South AfricaSETI Institute , 339 Bernardo Avenue, Suite 200, Mountain View, CA 94043, USAOxford Theoretical Physics , Beecroft Building, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UKDepartment of Astrophysics/IMAPP , Radboud University, PO Box 9010, 6500 GL, Nijmegen, The Netherlands; SRON, Netherlands Institute for Space Research , Niels Bohrweg 4, 2333 CA, Leiden, The NetherlandsAstrophysics, Department of Physics, The University of Oxford , Keble Road, Oxford OX1 3RH, UK ; joe.bright@physics.ox.ac.uk; Astrophysics Research Centre , School of Mathematics and Physics, Queen’s University Belfast, BT7 1NN, UKRadio Astronomy Lab, University of California , Berkeley, CA, USASETI Institute , 339 Bernardo Avenue, Suite 200, Mountain View, CA 94043, USA; Berkeley SETI Research Centre, University of California , Berkeley, CA 94720, USAAstrophysics, Department of Physics, The University of Oxford , Keble Road, Oxford OX1 3RH, UK ; joe.bright@physics.ox.ac.ukSETI Institute , 339 Bernardo Avenue, Suite 200, Mountain View, CA 94043, USAAstrophysics, Department of Physics, The University of Oxford , Keble Road, Oxford OX1 3RH, UK ; joe.bright@physics.ox.ac.ukAstrophysics, Department of Physics, The University of Oxford , Keble Road, Oxford OX1 3RH, UK ; joe.bright@physics.ox.ac.uk; Breakthrough Listen, Astrophysics, Department of Physics, The University of Oxford , Keble Road, Oxford OX1 3RH, UK; SETI Institute , 339 Bernardo Avenue, Suite 200, Mountain View, CA 94043, USA; Berkeley SETI Research Centre, University of California , Berkeley, CA 94720, USA; Department of Physics and Astronomy, University of Manchester , UK; University of Malta , Institute of Space Sciences and Astronomy, Msida, MSD2080, MaltaDespite being operational for only a short time, the Einstein Probe mission, with its large field of view and rapid localization capabilities, has already significantly advanced the study of rapid variability in the soft X-ray sky. We report the discovery of luminous and variable radio emission from the Einstein Probe fast X-ray transient EP240414a, the second such source with a radio counterpart. The radio emission at 3 GHz peaks at ∼30 days postexplosion and with a spectral luminosity ∼2 × 10 ^30 erg s ^−1 Hz ^−1 , similar to what is seen from long gamma-ray bursts, and distinct from other extragalactic transients including supernovae and tidal disruption events, although we cannot completely rule out emission from engine driven stellar explosions, e.g., the fast blue optical transients. An equipartition analysis of our radio data reveals that an outflow with at least a moderate bulk Lorentz factor (Γ ≳ 1.6) with a minimum energy of ∼10 ^48 erg is required to explain our observations. The apparent lack of a reported gamma-ray counterpart to EP240414a could suggest that an off-axis or choked jet could be responsible for the radio emission, although a low-luminosity gamma-ray burst may have gone undetected. Our observations are consistent with the hypothesis that a significant fraction of extragalactic fast X-ray transients are associated with the deaths of massive stars.https://doi.org/10.3847/1538-4357/adaaefExtragalactic radio sourcesRadio transient sourcesRelativistic jetsX-ray transient sourcesGamma-ray burstsTransient sources |
| spellingShingle | Joe S. Bright Francesco Carotenuto Rob Fender Carmen Choza Andrew Mummery Peter G. Jonker Stephen J. Smartt David R. DeBoer Wael Farah James Matthews Alexander W. Pollak Lauren Rhodes Andrew Siemion The Radio Counterpart to the Fast X-Ray Transient EP240414a The Astrophysical Journal Extragalactic radio sources Radio transient sources Relativistic jets X-ray transient sources Gamma-ray bursts Transient sources |
| title | The Radio Counterpart to the Fast X-Ray Transient EP240414a |
| title_full | The Radio Counterpart to the Fast X-Ray Transient EP240414a |
| title_fullStr | The Radio Counterpart to the Fast X-Ray Transient EP240414a |
| title_full_unstemmed | The Radio Counterpart to the Fast X-Ray Transient EP240414a |
| title_short | The Radio Counterpart to the Fast X-Ray Transient EP240414a |
| title_sort | radio counterpart to the fast x ray transient ep240414a |
| topic | Extragalactic radio sources Radio transient sources Relativistic jets X-ray transient sources Gamma-ray bursts Transient sources |
| url | https://doi.org/10.3847/1538-4357/adaaef |
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