Fermi-LAT detections of novae V1723 Sco and V6598 Sgr
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2025
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| author | Fauverge, P. Jean, P. Sokolovsky, K. Cheung, C. C. Lemoine-Goumard, M. Grondin, M. -H. Chomiuk, L. Dickenson, A. Linford, J. D. Mukai, K. Sokoloski, J. L. |
| author_facet | Fauverge, P. Jean, P. Sokolovsky, K. Cheung, C. C. Lemoine-Goumard, M. Grondin, M. -H. Chomiuk, L. Dickenson, A. Linford, J. D. Mukai, K. Sokoloski, J. L. |
| contents | Context. Numerous classical novae have been observed to emit γ-rays (E > 100 MeV) detected by the Fermi-LAT. The prevailing hypothesis attributes this emission to the interaction of accelerated particles within shocks in the nova ejecta. However, the lack of non-thermal X-ray detection coincident with the γ-rays remains a challenge to this theory. Methods. We performed similar analyses of the Fermi-LAT data for both novae to determine the duration, localization, and spectral properties of the γ-ray emission. These results were compared with optical data from the AAVSO database and X-ray observations from NuSTAR, available for V1723 Sco 2024 only, to infer the nature of the accelerated particles. Finally, we used a physical emission model to extract key parameters related to particle acceleration. Results. V1723 Sco 2024 was found to be a very bright γ-ray source with an emission duration of 15 days allowing us to constrain the spectral index and the total energy of accelerated protons. Despite early NuSTAR observations, no non-thermal X-ray emission was detected simultaneously with the γ-rays. However, unexpected γ-ray and thermal hard X-ray emission were observed more than 40 days after the nova outburst, suggesting that particle acceleration can occur even several weeks post-eruption. V6598 Sgr 2023, on the other hand, was detected by the Fermi-LAT at a significance level of 4σover just two days, one of the shortest γ-ray emission durations ever recorded, coinciding with a rapid decline in optical brightness. Finally, the high ratio of γ-ray to optical luminosities and γ-ray to X-ray luminosities for both novae, as well as the curvature of the γ-ray spectrum of V1723 Sco below 500 MeV, are all more consistent with the hadronic than the leptonic scenario for γ-ray generation in novae. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2512_14198 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Fermi-LAT detections of novae V1723 Sco and V6598 Sgr Fauverge, P. Jean, P. Sokolovsky, K. Cheung, C. C. Lemoine-Goumard, M. Grondin, M. -H. Chomiuk, L. Dickenson, A. Linford, J. D. Mukai, K. Sokoloski, J. L. High Energy Astrophysical Phenomena Context. Numerous classical novae have been observed to emit γ-rays (E > 100 MeV) detected by the Fermi-LAT. The prevailing hypothesis attributes this emission to the interaction of accelerated particles within shocks in the nova ejecta. However, the lack of non-thermal X-ray detection coincident with the γ-rays remains a challenge to this theory. Methods. We performed similar analyses of the Fermi-LAT data for both novae to determine the duration, localization, and spectral properties of the γ-ray emission. These results were compared with optical data from the AAVSO database and X-ray observations from NuSTAR, available for V1723 Sco 2024 only, to infer the nature of the accelerated particles. Finally, we used a physical emission model to extract key parameters related to particle acceleration. Results. V1723 Sco 2024 was found to be a very bright γ-ray source with an emission duration of 15 days allowing us to constrain the spectral index and the total energy of accelerated protons. Despite early NuSTAR observations, no non-thermal X-ray emission was detected simultaneously with the γ-rays. However, unexpected γ-ray and thermal hard X-ray emission were observed more than 40 days after the nova outburst, suggesting that particle acceleration can occur even several weeks post-eruption. V6598 Sgr 2023, on the other hand, was detected by the Fermi-LAT at a significance level of 4σover just two days, one of the shortest γ-ray emission durations ever recorded, coinciding with a rapid decline in optical brightness. Finally, the high ratio of γ-ray to optical luminosities and γ-ray to X-ray luminosities for both novae, as well as the curvature of the γ-ray spectrum of V1723 Sco below 500 MeV, are all more consistent with the hadronic than the leptonic scenario for γ-ray generation in novae. |
| title | Fermi-LAT detections of novae V1723 Sco and V6598 Sgr |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2512.14198 |