The multiwavelength view of shocks in the fastest nova V1674 Her

K. V. Sokolovsky*, T. J. Johnson, S. Buson, P. Jean, C. C. Cheung, K. Mukai, L. Chomiuk, E. Aydi, B. Molina, A. Kawash, J. D. Linford, A. J. Mioduszewski, M. P. Rupen, J. L. Sokoloski, M. N. Williams, E. Steinberg, I. Vurm, B. D. Metzger, K. L. Page, M. OrioR. M. Quimby, A. W. Shafter, H. Corbett, S. Bolzoni, J. Deyoung, K. Menzies, F. D. Romanov, M. Richmond, J. Ulowetz, T. Vanmunster, G. Williamson, D. J. Lane, M. Bartnik, M. Bellaver, E. Bruinsma, E. Dugan, J. Fedewa, C. Gerhard, S. Painter, D. M. Peterson, J. E. Rodriguez, C. Smith, H. Sullivan, S. Watson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Classical novae are shock-powered multiwavelength transients triggered by a thermonuclear runaway on an accreting white dwarf. V1674 Her is the fastest nova ever recorded (time to declined by two magnitudes is t2 = 1.1 d) that challenges our understanding of shock formation in novae. We investigate the physical mechanisms behind nova emission from GeV γ-rays to cm-band radio using coordinated Fermi-LAT, NuSTAR, Swift, and VLA observations supported by optical photometry. Fermi-LAT detected short-lived (18 h) 0.1-100 GeV emission from V1674 Her that appeared 6 h after the eruption began; this was at a level of (1.6 ± 0.4) × 10-6 photons cm-2 s-1. Eleven days later, simultaneous NuSTAR and Swift X-ray observations revealed optically thin thermal plasma shock-heated to kTshock = 4 keV. The lack of a detectable 6.7 keV Fe Kα emission suggests super-solar CNO abundances. The radio emission from V1674 Her was consistent with thermal emission at early times and synchrotron at late times. The radio spectrum steeply rising with frequency may be a result of either free-free absorption of synchrotron and thermal emission by unshocked outer regions of the nova shell or the Razin-Tsytovich effect attenuating synchrotron emission in dense plasma. The development of the shock inside the ejecta is unaffected by the extraordinarily rapid evolution and the intermediate polar host of this nova.

Original languageAmerican English
Pages (from-to)5453-5472
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - 1 Jun 2023

Bibliographical note

Publisher Copyright:
© 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.


  • novae, cataclysmic variables
  • stars: individual: V1674 Her
  • transients: novae
  • white dwarfs


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