47 Tucanae X9
X-ray binary
From Wikipedia, the free encyclopedia
47 Tucanae X9 (also known as 47 Tuc X9) is an ultracompact low-mass X-ray binary (LMXB) located within the globular cluster 47 Tucanae, one of the brightest and most massive globular cluster in the Milky Way Galaxy, situated approximately 14,800 light-years away in the constellation of Tucana.[5] The system is notable for being the first confirmed black hole-white dwarf binary in the Milky Way, with an exceptionally short orbital period of approximately 28.18 minutes.[6]
Artistic representation of 47 Tucanae X9 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Tucana[1] |
| Right ascension | 00h 24m 04.26s[2] |
| Declination | −72° 04′ 58.0″[2] |
| Apparent magnitude (V) | 19.772[3] |
| Characteristics | |
| Evolutionary stage | Black hole + white dwarf[4] |
| Spectral type | WD |
| Orbit | |
| Period (P) | 28.18 minutes |
| Other designations | |
| 47 Tuc X9, RX J0021.8-7221, CXOGlb J002404.2-720458[2] | |
| Database references | |
| SIMBAD | data |
Discovery and observations
47 Tuc X9 was discovered using NASA Chandra X-ray Observatory, NuSTAR and the Australia Telescope Compact Array (ATCA).[7][8] Initially the system was classified as a cataclysmic variable with a white dwarf primary,[9] subsequent radio and X-ray observations reclassified it as an LMXB with a black hole. An alternative hypothesis of a neutron star (possibly a transitional millisecond pulsar) was considered but deemed less likely due to the absence of pulsations and the system's ultracompact orbit.[10]
Formation and evolution
The ultracompact orbit of 47 Tuc X9 likely resulted from dynamical interactions in the dense environment of 47 Tucanae, such as a black hole capturing a white dwarf or evolving from a black hole/helium-star binary through mass transfer and gravitational wave emission. The high stellar density of the globular cluster facilitates the formation of such compact binaries.[6]