GJ 2069
Star system in the constellation Cancer
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GJ 2069 is a quintuple star system located 54 light-years (17 parsecs) away in the constellation Cancer. It appears near the Beehive Cluster in the sky, but it is closer than the cluster and is not a member of it. The system is composed of two sub-systems, GJ 2069 A & B, also known by their variable star designations CU Cancri and CV Cancri; both are binary, and GJ 2069 A has a third companion star, making five stars in total. All five stars are red dwarfs.
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Cancer[1] |
| A | |
| Right ascension | 08h 31m 37.57418s[2] |
| Declination | +19° 23′ 39.3980″[2] |
| Apparent magnitude (V) | 11.81[3] |
| B | |
| Right ascension | 08h 31m 37.42279s[4] |
| Declination | +19° 23′ 49.2821″[4] |
| Apparent magnitude (V) | 14.83[4] |
| Characteristics | |
| A | |
| Evolutionary stage | main sequence |
| Spectral type | M3.5Ve + M3.5Ve[5] |
| Variable type | UV Cet+EB[6] |
| B | |
| Evolutionary stage | main sequence |
| Spectral type | M4.0Ve[4] |
| Variable type | UV Cet[7] |
| Astrometry | |
| A | |
| Proper motion (μ) | RA: −228.694 mas/yr[2] Dec.: −119.919 mas/yr[2] |
| Parallax (π) | 60.0602±0.0356 mas[2] |
| Distance | 54.30 ± 0.03 ly (16.650 ± 0.010 pc) |
| Absolute magnitude (MV) | 11.95 + 12.31[5] |
| B | |
| Radial velocity (Rv) | 7.83±1.21[8] km/s |
| Proper motion (μ) | RA: −232.878 mas/yr[8] Dec.: −128.911 mas/yr[8] |
| Parallax (π) | 60.2485±0.0764 mas[8] |
| Distance | 54.14 ± 0.07 ly (16.60 ± 0.02 pc) |
| C | |
| Proper motion (μ) | RA: −207.443 mas/yr[9] Dec.: −125.513 mas/yr[9] |
| Parallax (π) | 60.6896±0.1458 mas[9] |
| Distance | 53.7 ± 0.1 ly (16.48 ± 0.04 pc) |
| Orbit[10] | |
| Primary | Aa |
| Name | Ab |
| Period (P) | 2.77146871(34) d |
| Inclination (i) | 86.34±0.03° |
| Details | |
| Aa | |
| Mass | 0.4358±0.0008[10] M☉ |
| Radius | 0.4122±0.0015[11] R☉ |
| Luminosity | 0.0167[5] L☉ |
| Surface gravity (log g) | 4.804±0.011[5] cgs |
| Temperature | 3160±150[5] K |
| Ab | |
| Mass | 0.3998±0.0014[10] M☉ |
| Radius | 0.3817±0.0024[11] R☉ |
| Luminosity | 0.0131[5] L☉ |
| Surface gravity (log g) | 4.854±0.021[5] cgs |
| Temperature | 3125±150[5] K |
| Other designations | |
| GJ 2069, CCDM J08316+1924AB | |
| A: CU Cnc, HIP 41824, L 1251-12, LP 425-72, LTT 12221, NLTT 19685[3] | |
| B: CV Cnc, L 1251-13, LP 425-7, LTT 12222, NLTT 19684[4] | |
| Database references | |
| SIMBAD | A |
| BC | |
| B | |
| C | |
| ARICNS | A |
| B | |
According to a 2003 study, the system is likely a member of the Castor Moving Group, with an age of 320 million years,[5] but a 2024 study of the stellar magnetic fields found that the system is likely at least 1 billion years old.[10]
System
| GJ 2069 Aa (CU Cnc A) | |||||||||||||
| Period = 2.8 d | |||||||||||||
| GJ 2069 Ab (CU Cnc B) | |||||||||||||
| 0.68″ separation | |||||||||||||
| GJ 2069 D | |||||||||||||
| 12″ separation | |||||||||||||
| GJ 2069 B (CV Cnc A) | |||||||||||||
| 0.36″ separation | |||||||||||||
| GJ 2069 C (CV Cnc B) | |||||||||||||
Hierarchy of orbits in the GJ 2069 system
GJ 2069 A & B are separated by 12 arcseconds.[12] Both are flare stars.[6][7]
GJ 2069 A (CU Cancri)
GJ 2069 A, also known as CU Cancri, is a close eclipsing binary orbiting every 2.8 days. Both stars are red dwarfs around 40% the mass of the Sun.[5] It was found to be a binary in 1999, and was the third known M-dwarf eclipsing binary, after CM Draconis and YY Geminorum (Castor C).[14] The stars appear fainter than other stars of the same mass,[5] likely due to high starspot coverage.[15]
GJ 2069 A also has a third companion star at a separation of 0.68 arcseconds, designated GJ 2069 D. It was found in 2001.[12]
GJ 2069 B (CV Cancri)
GJ 2069 B, also known as CV Cancri, is a binary pair of red dwarfs, separated by 0.36 arcseconds. The companion star is also called GJ 2069 C.[12] It was resolved as a binary in 1999.[17]