47 Tucanae X9

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47 Tucanae X9
47 Tucanae X9.jpg
Artistic Representation of 47 Tucanae X9
Observation data
Epoch J2000.0       Equinox J2000.0
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[ citation needed ]
Other designations
47 Tuc X9, RX J0021.8-7221 [2]
Database references
SIMBAD data

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 (NGC 104), 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. 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. [5] [6] [7]

Contents

Discovery and Observations

47 Tuc X9 was discovered using NASA Chandra X-ray Observatory, NuSTAR and the Australia Compact Telescope Array (ATCA). [8] [9] [10]

Initially the system was classified as a cataclysmic variable with a white dwarf primary, [11] 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. [12]

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. [5]

Significance

47 Tuc X9 is a rare example of a black hole-white dwarf binary in a globular cluster, providing insights into binary evolution, accretion processes, and dynamical interactions in dense stellar environments. Its discovery as the first confirmed ultracompact black hole binary in the Milky Way enhances our understanding of black hole populations in globular clusters. [13]

Recent Study

Ultradeep ATCA imaging in 2024 identified a faint central compact radio source in 47 Tucanae, unrelated to X9, highlighting the cluster's richness in compact objects. No significant updates to X9's classification have been reported since its reclassification in 2017. [14]

References

  1. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific . 99 (617): 695. Bibcode:1987PASP...99..695R. doi: 10.1086/132034 . Constellation record for this object at VizieR.
  2. 1 2 3 "RX J0021.8-7221". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2025-10-01.
  3. ↑ Albrow, Michael D.; Gilliland, Ronald L.; Brown, Timothy M.; Edmonds, Peter D.; Guhathakurta, Puragra; Sarajedini, Ata (2001). "The Frequency of Binary Stars in the Core of 47 Tucanae". The Astrophysical Journal. 559 (2): 1060. arXiv: astro-ph/0105441 . Bibcode:2001ApJ...559.1060A. doi:10.1086/322353.
  4. ↑ "Chandra :: Photo Album :: X9 in 47 Tucanae :: More Images of X9 in 47 Tucanae". chandra.harvard.edu. Retrieved 2025-09-17.
  5. 1 2 Bahramian, Arash; Heinke, Craig O.; Tudor, Vlad; Miller-Jones, James C. A.; Bogdanov, Slavko; Maccarone, Thomas J.; Knigge, Christian; Sivakoff, Gregory R.; Chomiuk, Laura (2017-02-07). "The ultracompact nature of the black hole candidate X-ray binary 47 Tuc X9". Monthly Notices of the Royal Astronomical Society. 467 (2): 2199–2216. arXiv: 1702.02167 . Bibcode:2017MNRAS.467.2199B. doi: 10.1093/mnras/stx166 .
  6. ↑ "Artist's Impression of 47 Tucanae X9 - NASA" . Retrieved 2025-09-17.
  7. ↑ "Star Discovered in Closest Known Orbit Around Likely Black Hole - NASA". 2017-03-13. Retrieved 2025-09-18.
  8. ↑ "Chandra :: Photo Album :: X9 in 47 Tucanae :: More Images of X9 in 47 Tucanae". chandra.harvard.edu. Retrieved 2025-09-17.
  9. ↑ Byrd, Deborah (2017-03-15). "Closest-yet star to black hole | Space | EarthSky" . Retrieved 2025-09-17.
  10. ↑ "Chandra :: Photo Album :: 47 Tucanae :: March 13, 2017". chandra.harvard.edu. Retrieved 2025-10-01.
  11. ↑ Paresce, Francesco; De Marchi, Guido; Ferraro, Francesco R. (November 1992). "Possible cataclysmic variable in the core of the globular cluster 47 Tucanae". Nature. 360 (6399): 46–48. Bibcode:1992Natur.360...46P. doi:10.1038/360046a0. ISSN   1476-4687.
  12. ↑ News Staff (2017-03-14). "Astronomers Find Record-Breaking White-Dwarf-Black-Hole Binary in Globular Cluster 47 Tucanae | Astronomy | Sci-News.com". Sci.News: Breaking Science News. Retrieved 2025-09-17.
  13. ↑ Miller-Jones, J. C. A.; Strader, J.; Heinke, C. O.; Maccarone, T. J.; Berg, M. van den; Knigge, C.; Chomiuk, L.; Noyola, E.; Russell, T. D. (2015-09-08). "Deep radio imaging of 47 Tuc identifies the peculiar X-ray source X9 as a new black hole candidate". Monthly Notices of the Royal Astronomical Society. 453 (4): 3919–3932. arXiv: 1509.02579 . Bibcode:2015MNRAS.453.3918M. doi: 10.1093/mnras/stv1869 .
  14. ↑ Paduano, Alessandro; Bahramian, Arash; Miller-Jones, James C. A.; Kawka, Adela; Galvin, Tim J.; Rivera Sandoval, Liliana; Kamann, Sebastian; Strader, Jay; Chomiuk, Laura; Heinke, Craig O.; Maccarone, Thomas J.; Dreizler, Stefan (January 2024). "Ultradeep ATCA Imaging of 47 Tucanae Reveals a Central Compact Radio Source". The Astrophysical Journal. 961 (1): 54. arXiv: 2401.09692 . Bibcode:2024ApJ...961...54P. doi: 10.3847/1538-4357/ad0e68 . ISSN   0004-637X.
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