Year: 2026
Type: preprint
Abstract: We report the discovery and early outburst evolution of the new Galactic magnetar EP J223759.5+531421, detected by the Einstein Probe Wide-field X-ray Telescope on 2026 June 28. Follow-up observations with Einstein Probe, XMM--Newton, NuSTAR, SVOM, and IXPE revealed coherent X-ray pulsations at P ~ 6s and an average period derivative of Pdot ~ 2.8x10^{-12} s/s. These values imply a nominal polar dipolar magnetic field of B_dip ~ 2.6x10^{14} Gauss and a characteristic age of tau_c ~ 34 kyr, although the structured timing residuals suggest possible torque variability. The rms pulsed fraction is approximately 20-25% below ~7 keV and decreases at higher energies. The broadband spectra require multiple thermal components and a hard power-law tail. Adopting a distance of 3.3 kpc, the 0.5-30 keV luminosity declined from 1.2x10^{35} to 5.7x10^{34} erg/s during the first month, accompanied by a decrease in the inferred thermal-emitting areas. At this distance, the Galactic latitude b=-4.56 deg corresponds to a height of approximately 0.26 kpc below the Galactic plane, which is difficult to reconcile with the nominal characteristic age under a simple midplane-birth scenario even for an extreme proper motion velocity. Short X-ray bursts independently confirm the magnetar nature of the source. No near-infrared or radio counterpart were detected by GTC, Medicina or FAST, respectively, down to K_s>21 mag and S_{1.25 GHz} <2.3 microJy. These observations demonstrate the potential of the Einstein Probe WXT monitoring to uncover previously quiescent Galactic magnetars and follow their outbursts from their earliest observed stages.
Source: arXiv (Cornell University)
Authors: Rea, N., Zelati, F. Coti, Borghese, A., Wang, Y. L., Yang, H., Mao, X., Dai, C. -Y., Arrigoni, E., Bai, J., Bernardi, G., Burgay, M., Cao, S., Coleiro, A., De Grandis, D., Esposito, P., Feng, H., Fu, Y. -C., Geminardi, A., Götz, D., Guillot, S., Huang, Y., Imbrogno, M., Israel, G. L., Jin, C., Kong, A., Li, Y., Lin, L., Liu, C. -S., Maitra, C., Marino, A., Mereghetti, S., Ness, J. -U., Ng, S., Pilia, M., Possenti, A., Sun, H., Tao, L., Taverna, R., Tiengo, A., Turolla, R., Yuan, W., Zane, S., Zhang, B., Zhang, L. -X., Zhang, Z., Zhu, W. -W., Zou, Y. -C.
Institutions: Institute of Space Sciences, Institut d'Estudis Espacials de Catalunya, European Space Agency, European Space Astronomy Centre, Chinese Academy of Sciences, National Astronomical Observatories, University of Chinese Academy of Sciences, Nanjing University, Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano, Istituto di Radioastronomia di Bologna, Osservatorio Astronomico di Cagliari, National Institute for Astrophysics, Centre National de la Recherche Scientifique, Université Paris Cité, Laboratoire AstroParticule et Cosmologie, Istituto Universitario di Studi Superiori di Pavia, Institute of High Energy Physics, Beijing Normal University, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, Astrophysique, Instrumentation et Modélisation, Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, Astronomical Observatory of Rome, National Tsing Hua University, Max Planck Institute for Extraterrestrial Physics, Inter-University Centre for Astronomy and Astrophysics, University of Hong Kong, University of Padua, University College London
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Aeronautics and Space Administration, California Institute of Technology, European Space Agency, European Commission, National Natural Science Foundation of China, Chinese Academy of Sciences, Centre National d’Etudes Spatiales, Università degli Studi di Trento, Instituto de Astrofísica de Canarias, Jet Propulsion Laboratory, National Astronomical Observatories, Chinese Academy of Sciences
OpenAlex ID: W7214074398