Eta Gruis
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Grus[1] |
| Right ascension | 22h 45m 37.88194s[2] |
| Declination | −53° 30′ 00.4315″[2] |
| Apparent magnitude (V) | 4.85[3] |
| Characteristics | |
| Evolutionary stage | red giant branch[2] |
| Spectral type | K2 III CNIV[4] |
| U−B color index | +1.17[3] |
| B−V color index | +1.18[3] |
| Astrometry | |
| Radial velocity (Rv) | +27.8±2.8[5] km/s |
| Proper motion (μ) | RA: +30.717[2] mas/yr Dec.: +17.334[2] mas/yr |
| Parallax (π) | 7.2136±0.1013 mas[2] |
| Distance | 452 ± 6 ly (139 ± 2 pc) |
| Absolute magnitude (MV) | −0.68[1] |
| Details | |
| Mass | 4.4[2] M☉ |
| Radius | 33[2] R☉ |
| Luminosity | 355[2] L☉ |
| Surface gravity (log g) | 1.52[2] cgs |
| Temperature | 4,491[2] K |
| Rotational velocity (v sin i) | 3.3[6] km/s |
| Other designations | |
| η Gru, CPD−54°10123, FK5 3821, HD 215369, HIP 112374, HR 8655, SAO 247570, WDS J22456-5330A[7] | |
| Database references | |
| SIMBAD | data |
Eta Gruis, Latinized from η Gruis, is a solitary[8] star in the southern constellation of Grus. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.85.[3] Based upon an annual parallax shift of 7.2 mas as seen from the Earth, the system is located about 452 light years from the Sun. The star is drifting further away with a radial velocity of +28 km/s.
This object is an evolved K-type giant star with a stellar classification of K2 III CNIV,[4] where the suffix notation indicates this is an intermediate CN star. It is a periodic microvariable with an amplitude of 0.0055 magnitude and a frequency of 0.36118 cycles per day.[9] With the supply of hydrogen exhausted at its core, the star has expanded and cooled, now having 33 times the Sun's girth. It is radiating 355 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4491 K.[2]
Eta Gruis has a magnitude 11.5 visual companion located at an angular separation of 25.6″ along a position angle of 187°, as of 2012.[10]
References
[edit]- ^ a b 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 e f g h i j k l Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
- ^ a b Houk, Nancy; Cowley, A. P. (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
- ^ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
- ^ De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (2014). "A catalog of rotational and radial velocities for evolved stars. V. Southern stars". Astronomy and Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762.
- ^ "eta Gru". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-06-28.
- ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
- ^ Koen, Chris; Eyer, Laurent (2002), "New periodic variables from the Hipparcos epoch photometry", Monthly Notices of the Royal Astronomical Society, 331 (1): 45–59, arXiv:astro-ph/0112194, Bibcode:2002MNRAS.331...45K, doi:10.1046/j.1365-8711.2002.05150.x, S2CID 10505995.
- ^ Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
