Nature of 4FGL J2249.4+6229: Evidence for a redback system with a cool companion and low X-ray and $γ$-ray luminosities
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| Autores principales: | , , , |
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| Formato: | Preprint |
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2026
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| _version_ | 1866910245644664832 |
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| author | Karpova, A. V. Zyuzin, D. A. Zharikov, S. V. Gilfanov, M. R. |
| author_facet | Karpova, A. V. Zyuzin, D. A. Zharikov, S. V. Gilfanov, M. R. |
| contents | We report the identification of the likely X-ray and optical counterpart to the unassociated Fermi source 4FGL J2249.4+6229. To clarify its nature, we investigate the X-ray data from Swift/XRT and SRG/eROSITA as well as photometric data from optical catalogues and archival spectroscopic data from the Gemini-North telescope. Using Zwicky Transient Facility data spanning over 6.6 yr, we confirmed a period of $\approx$5.6 h likely associated with the orbital motion in a binary system. The folded light curves have a smooth sinusoidal shape with two peaks per period and the amplitude of $\approx$0.2 mag. The X-ray spectra of the source are well fitted by an absorbed power law with the photon index of $\approx$2.0 and unabsorbed flux of $\approx$1.4$\times10^{-13}$ erg s$^{-1}$ cm$^{-2}$. All these together with the X-ray to optical flux ratio of $\sim$0.2 implies that 4FGL J2249.4+6229 is a promising redback candidate. Fitting the optical light curves with the direct heating model, we obtained the companion mass of $\approx$0.5 M$_\odot$ and temperature of $\approx$3600 K implying an M-type star. This places it among the coldest and most massive companions known in redback systems.Optical spectra confirms the M-type star and shows the broad asymmetric H$α$ emission line. For the distance of 500--550 pc derived from the optical data, the source can be the redback with the lowest X-ray and $γ$-ray luminosities. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_22271 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Nature of 4FGL J2249.4+6229: Evidence for a redback system with a cool companion and low X-ray and $γ$-ray luminosities Karpova, A. V. Zyuzin, D. A. Zharikov, S. V. Gilfanov, M. R. High Energy Astrophysical Phenomena We report the identification of the likely X-ray and optical counterpart to the unassociated Fermi source 4FGL J2249.4+6229. To clarify its nature, we investigate the X-ray data from Swift/XRT and SRG/eROSITA as well as photometric data from optical catalogues and archival spectroscopic data from the Gemini-North telescope. Using Zwicky Transient Facility data spanning over 6.6 yr, we confirmed a period of $\approx$5.6 h likely associated with the orbital motion in a binary system. The folded light curves have a smooth sinusoidal shape with two peaks per period and the amplitude of $\approx$0.2 mag. The X-ray spectra of the source are well fitted by an absorbed power law with the photon index of $\approx$2.0 and unabsorbed flux of $\approx$1.4$\times10^{-13}$ erg s$^{-1}$ cm$^{-2}$. All these together with the X-ray to optical flux ratio of $\sim$0.2 implies that 4FGL J2249.4+6229 is a promising redback candidate. Fitting the optical light curves with the direct heating model, we obtained the companion mass of $\approx$0.5 M$_\odot$ and temperature of $\approx$3600 K implying an M-type star. This places it among the coldest and most massive companions known in redback systems.Optical spectra confirms the M-type star and shows the broad asymmetric H$α$ emission line. For the distance of 500--550 pc derived from the optical data, the source can be the redback with the lowest X-ray and $γ$-ray luminosities. |
| title | Nature of 4FGL J2249.4+6229: Evidence for a redback system with a cool companion and low X-ray and $γ$-ray luminosities |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2605.22271 |