81 Cancri
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cancer |
| Right ascension | 09h 12m 17.547s[1] |
| Declination | +14° 59′ 45.78″[1] |
| Apparent magnitude (V) | 6.49[2] |
| Characteristics | |
| Spectral type | G8V[3] + K1V[3] / L8[4][5] + ~L8[5] |
| B−V color index | 0.731±0.004[2] |
| Variable type | Constant[2] |
| Astrometry | |
| Radial velocity (Rv) | 49.8252±0.076[6] km/s |
| Proper motion (μ) | RA: −523.619 mas/yr[1] Dec.: +244.282 mas/yr[1] |
| Parallax (π) | 49.1493±0.3467 mas[1] |
| Distance | 66.4 ± 0.5 ly (20.3 ± 0.1 pc) |
| Absolute magnitude (MV) | +4.95[2] |
| Orbit[6] | |
| Primary | 81 Cancri A |
| Companion | 81 Cancri B |
| Period (P) | 988.058±0.34698 d |
| Semi-major axis (a) | 115.4±0.63″ |
| Eccentricity (e) | 0.433256±0.0034 |
| Inclination (i) | 124.1±0.64° |
| Longitude of the node (Ω) | 317.6±0.46° |
| Periastron epoch (T) | 1982.690±0.0040 |
| Argument of periastron (ω) (secondary) | 170.731±0.81° |
| Argument of periastron (ω) (primary) | 350.731±0.81° |
| Semi-amplitude (K1) (primary) | 11.4908±0.11 km/s |
| Semi-amplitude (K2) (secondary) | 12.1317±0.14 km/s |
| Details | |
| 81 Cnc A | |
| Mass | 0.89±0.029[6] M☉ |
| Radius | 0.82[7] R☉ |
| Luminosity | 1.03[2] L☉ |
| Surface gravity (log g) | 4.55[7] cgs |
| Temperature | 5,430[7] K |
| Metallicity [Fe/H] | −0.28[7] dex |
| 81 Cnc B | |
| Mass | 0.85±0.026[6] M☉ |
| Radius | 0.81[7] R☉ |
| Surface gravity (log g) | 4.56[7] cgs |
| Temperature | 5,360[7] K |
| Metallicity [Fe/H] | −0.28[7] dex |
| Other designations | |
| π1 Cnc, 81 Cancri, GJ 337, HD 79096, HIP 45170, SAO 98427, WDS J09123+1500 | |
| Database references | |
| SIMBAD | data |
81 Cancri is a stellar system in the zodiac constellation of Cancer. It has the Bayer designation Pi1 Cancri, which is Latinized from π1 Cancri, and abbreviated Pi1 Cnc or π1 Cnc; 81 Cancri is the star's Flamsteed designation. The main component of the system is a close binary, while a brown dwarf binary is located at a wide separation. The primary is just bright enough to be visible to the naked eye, having an apparent visual magnitude of 6.49.[2] Its position near the ecliptic means it is subject to lunar occultations.[8]
Based on parallax measurements, this system is located at a distance of 66 light-years (20 pc) from the Sun. HD 164595 has a large proper motion, traversing the celestial sphere at an angular rate of 0.578″ yr−1.[9] It is drifting further away with a line of sight velocity of 49.8 km/s.[6]
Components
[edit]81 Cancri was found to be a close visual binary by W. S. Finsen in 1959.[10] Their orbit has a period of 2.7 yr with an eccentricity of 0.433. The primary is a G-type main-sequence star with a stellar classification of G8V.[3] It has 89%[6] of the mass of the Sun and 82% of the Sun's radius.[7] This star is radiating a similar luminosity as the Sun from its photosphere with an effective temperature of 5,430 K.[7] The secondary is a K-type main-sequence star with a class of K1V.[3] It has a similar mass and temperature as the primary, being only ~0.04 M☉ lower in mass and a few hundred kelvin cooler.
A brown dwarf component in the system was detected in 2001.[4] The source 2MASSW J0912145+145940 (2M0912+14) in the 2MASS catalogue was identified as having a common proper motion with the AB binary, and subsequent observations confirmed the brown dwarf nature of the companion. The new component, 81 Cancri C, was found to have a spectral type of L8, near to the L-T transition. Separated from the primary components by 43 arcseconds and at a distance of 20.4 parsecs, the brown dwarf has a minimum physical separation of approximately 880 AU.
The brown dwarf was found to be about half a magnitude brighter in the JHK bands than expected, compared to others of similar spectral type and known distance. The system was not found to not be particularly young to some confidence, so it was possible that component C could itself be a close binary not resolved by 2MASS. This was confirmed in 2006[5] as the source was found to be slightly oblong, caused by two components of similar spectral types. These two brown dwarfs, components C and D, have a separation of approximately 11 AU, and their mutual orbit likely takes on order of 150 years due to the small masses involved.
See also
[edit]References
[edit]- ^ a b c d Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c d e f Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
- ^ a b c d Richichi, A.; et al. (2000). "New binary stars discovered by lunar occultations. V". Astronomy and Astrophysics. 361: 594. Bibcode:2000A&A...361..594R.
- ^ a b Wilson, J. C.; et al. (2001). "Three Wide-Separation L Dwarf Companions from the Two Micron All Sky Survey: Gliese 337C, Gliese 618.1B, and HD 89744B". The Astronomical Journal. 122 (4): 1989–2000. arXiv:astro-ph/0108424. Bibcode:2001AJ....122.1989W. doi:10.1086/323134. S2CID 17789028.
- ^ a b c Burgasser, Adam J.; et al. (2006). "Multiplicity among Widely Separated Brown Dwarf Companions to Nearby Stars: Gliese 337CD". The Astronomical Journal. 129 (6): 2849–2855. arXiv:astro-ph/0503379. Bibcode:2005AJ....129.2849B. doi:10.1086/430218. S2CID 16980949.
- ^ a b c d e f Pourbaix, D. (2000). "Resolved double-lined spectroscopic binaries: A neglected source of hypothesis-free parallaxes and stellar masses". Astronomy and Astrophysics Supplement Series. 145 (2): 215–222. Bibcode:2000A&AS..145..215P. doi:10.1051/aas:2000237.
- ^ a b c d e f g h i j Fuhrmann, Klaus (February 2008). "Nearby stars of the Galactic disc and halo - IV". Monthly Notices of the Royal Astronomical Society. 384 (1): 173–224. Bibcode:2008MNRAS.384..173F. doi:10.1111/j.1365-2966.2007.12671.x.
- ^ Richichi, A.; et al. (September 2000). "New binary stars discovered by lunar occultations. V". Astronomy and Astrophysics. 361: 594–600. Bibcode:2000A&A...361..594R.
- ^ Lépine, Sébastien; Shara, Michael M. (March 2005). "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)". The Astronomical Journal. 129 (3): 1483–1522. arXiv:astro-ph/0412070. Bibcode:2005AJ....129.1483L. doi:10.1086/427854. S2CID 2603568.
- ^ Griffin, R. F.; Griffin, R. E. M. (December 1982). "81 CANCRI (phi 347) - a visual binary which is spectroscopically double-lined". The Observatory. 102: 217–222. Bibcode:1982Obs...102..217G.
