Swift J1727.8-1613 (also known as J1727) is a ultraluminous low-mass x-ray binary 8,800 light years away with an orbital period of about 7.6 hours.[1][2] The compact object in the system is a stellar-mass black hole with a mass of at least 3.12±0.10 M☉︎, in orbit with an early K-type companion star.[1][3] The black hole's relativistic jet is the most resolved continuous X-ray binary jet, and one of the most physically extended X-ray binary jets yet discovered.[1][4] The system was first detected in August 2023.[1][3]
System properties
Light curves for Swift J1727.8−1613 in four photometric bands, showing several flares. Adapted from Vincentelli et al. (2025)[5]
The system reached a peak optical magnitude of approximately 12.7, making it an interest of research into black hole x-ray binaries. In x-ray wavelengths, J1727 transitions between soft and hard x-ray states.[3] In the soft state, the X-ray emission has a spectrum suggesting a geometrically thin, optically thick accretion disk. The accretion disk is believed to extend down to the innermost stable circular orbit of the black hole.[6][2]
Relativistic jets
In August 2023, a bright outburst from the binary system was detected that would last for another 10 months.[3] This observation was suggestive of a jet oriented in the north-south direction in the hard x-ray state.[2] The jet is believed to extend for 95-160 astronomical units.[1]
^ abcdMata Sánchez, D.; Torres, M. A. P.; Casares, J.; Muñoz-Darias, T.; Armas Padilla, M.; Yanes-Rizo, I. V. (2025). "Dynamical confirmation of a black hole in the X-ray transient Swift J1727.8−1613". Astronomy & Astrophysics. 693: A129. arXiv:2408.13310. Bibcode:2025A&A...693A.129M. doi:10.1051/0004-6361/202451960.
^Wood, Callan M.; Miller-Jones, James C. A.; Bahramian, Arash; Tingay, Steven J.; Prabu, Steve; Russell, Thomas D.; Atri, Pikky; Carotenuto, Francesco; Altamirano, Diego; Motta, Sara E.; Hyland, Lucas; Reynolds, Cormac; Weston, Stuart; Fender, Rob; Körding, Elmar; Maitra, Dipankar; Markoff, Sera; Migliari, Simone; Russell, David M.; Sarazin, Craig L.; Sivakoff, Gregory R.; Soria, Roberto; Tetarenko, Alexandra J.; Tudose, Valeriu (2024). "Swift J1727.8–1613 Has the Largest Resolved Continuous Jet Ever Seen in an X-Ray Binary". The Astrophysical Journal Letters. 971 (1): L9. arXiv:2405.12370. Bibcode:2024ApJ...971L...9W. doi:10.3847/2041-8213/ad6572.
