Is the Peculiar Galactic Center Transient Swift J174610.4-290018 A Nova Outburst?

Abstract

Swift J174610.4-290018 is a peculiar transient X-ray source in the Galactic center. First detected by Swift at the onset of an outburst in February 2024, it has since been observed intentionally and serendipitously by multiple X-ray observatories. To explore its long-term X-ray spectral and temporal behavior, we analyzed archival and recent observations from Chandra, Swift, and NuSTAR spanning from October 2000 to September 2025. The Chandra data reveal a previously unreported outburst in 2005, followed by an extended quiescent period of ~19 yr with a mean luminosity of ~10^32 erg/s. The 2024 outburst reached a peak 2-8 keV luminosity of L_X ~10^35 erg/s and decayed over ~120 days. In both quiescence and outburst, the spectra are well described by a high-temperature (~10 keV) thermal plasma, featuring prominent emission lines from neutral and highly ionized iron, and tentative chromium lines during the outburst. The long-term temporal and spectral properties disfavor the accretion disk corona scenario previously proposed based on early XRISM observations. Instead, a nova scenario provides a more natural explanation for the observed X-ray flux evolution, spectral characteristics, and possible repeated outbursts, which bear similarity to some known Galactic (recurrent) novae such as RS Oph. If confirmed, Swift J174610 would represent the first nova detected in the Galactic center, with important implications for the population of massive white dwarfs and wide binaries near Sgr A*. Continued multi-wavelength follow-up is essential to further elucidate the nature of this remarkable transient.