Gaia BH2
Gaia BH2 (Gaia DR3 5870569352746779008) is a binary system consisting of a red giant and what is very likely a stellar-mass black hole. Gaia BH2 is located about 3,800 light years away (1.16 kpc away) in the constellation of Centaurus, making it currently the third closest known black hole system to Earth. Gaia BH2 is the second black hole discovered from Gaia DR3 astrometric data, and Gaia BH1 and BH2 are likely the only black hole binaries which will be detected from Gaia DR3 data.[3]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 13h 50m 16.748s[1] |
| Declination | −59° 14′ 20.33″[1] |
| Apparent magnitude (V) | 12.711[2] |
| Characteristics | |
| Red giant | |
| Evolutionary stage | Red giant |
| Black hole | |
| Evolutionary stage | Stellar black hole |
| Astrometry | |
| Radial velocity (Rv) | −5.04±2.08[1] km/s |
| Proper motion (μ) | RA: −10.48±0.1 mas/yr[3] Dec.: −4.61±0.06 mas/yr[3] |
| Parallax (π) | 0.859 ± 0.018 mas[3] |
| Distance | 3,800 ± 80 ly (1,160 ± 20 pc) |
| Orbit[3] | |
| Period (P) | 1276.7±0.7 d |
| Semi-major axis (a) | 4.96±0.08 AU |
| Eccentricity (e) | 0.518±0.002 |
| Inclination (i) | 34.9±0.4° |
| Longitude of the node (Ω) | 266.9±0.5° |
| Periastron epoch (T) | 2457438.4±1.5 |
| Argument of periastron (ω) (secondary) | 131.0±0.5° |
| Semi-amplitude (K1) (primary) | 25.8±0.8 km/s |
| Details[3] | |
| Red giant | |
| Mass | 1.07±0.19 M☉ |
| Radius | 7.88±0.3 R☉ |
| Luminosity (bolometric) | 25±1.3 L☉ |
| Surface gravity (log g) | 2.71±0.24 cgs |
| Temperature | 4,604±87 K |
| Metallicity [Fe/H] | −0.22±0.02 dex |
| Rotational velocity (v sin i) | <1.5 km/s |
| Black hole | |
| Mass | 8.93±0.33 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The black hole and red giant orbit the system barycentre every 1,276 days, or around 3.5 years, with a moderate eccentricity of 0.518. The black hole's mass is around 8.93 M☉, which means its Schwarzschild radius should be about 26.4 km (16.4 mi). The red giant has a mass of 1.07 M☉ and a radius of 7.88 R☉. Its temperature is estimated at 4,604 K (4,331 °C; 7,828 °F).[3]
Discovery
Gaia BH2 was originally discovered as a black hole binary candidate in 2022, found via astrometric observations with Gaia, along with Gaia BH1. At that time it was not clear if Gaia BH2 did definitely harbour a black hole, but it was the only plausible candidate in the Gaia data other than Gaia BH1.[4][5] Later RV observations confirmed this black hole system and refined its orbital parameters.[3]
References
- Vallenari, A.; et al. (Gaia Collaboration) (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. arXiv:2208.00211. doi:10.1051/0004-6361/202243940. Gaia DR3 record for this source at VizieR.
- Zacharias, N.; Finch, C. T.; Girard, T. M.; Henden, A.; Bartlett, J. L.; Monet, D. G.; Zacharias, M. I. (2012-07-01). "VizieR Online Data Catalog: UCAC4 Catalogue (Zacharias+, 2012)". VizieR Online Data Catalog: I/322A. Bibcode:2012yCat.1322....0Z.
- El-Badry, Kareem; Rix, Hans-Walter; Cendes, Yvette; Rodriguez, Antonio C.; Conroy, Charlie; Quataert, Eliot; Hawkins, Keith; Zari, Eleonora; Hobson, Melissa; Breivik, Katelyn; Rau, Arne; Berger, Edo; Shahaf, Sahar; Seeburger, Rhys; Burdge, Kevin B. (2023-02-01). "A red giant orbiting a black hole". arXiv:2302.07880 [astro-ph.SR].
- El-Badry, Kareem; Rix, Hans-Walter; Quataert, Eliot; Howard, Andrew W.; Isaacson, Howard; Fuller, Jim; Hawkins, Keith; Breivik, Katelyn; Wong, Kaze W. K.; Rodriguez, Antonio C.; Conroy, Charlie; Shahaf, Sahar; Mazeh, Tsevi; Arenou, Frédéric; Burdge, Kevin B. (2023-01-01). "A Sun-like star orbiting a black hole". Monthly Notices of the Royal Astronomical Society. 518: 1057–1085. Bibcode:2023MNRAS.518.1057E. doi:10.1093/mnras/stac3140. ISSN 0035-8711.
- Tanikawa, Ataru; Hattori, Kohei; et al. (September 2022). "Search for a Black Hole Binary in Gaia DR3 Astrometric Binary Stars with Spectroscopic Data". arXiv:2209.05632 [astro-ph.SR].
