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ε Gruis, Latinised as Epsilon Gruis, is a blue-white hued star in the southern constellation of Grus. It is visible to the naked eye, having an apparent visual magnitude of 3.5. Based upon an annual parallax shift of 25.30 mas as measured from Earth, it is located around 129 light years from the Sun. The system may be moving closer to the Sun with a radial velocity of about −0.4 km/s.

This is an A-type subgiant of spectral type A2IVn, a star that has used up its core hydrogen and has begun to expand off the main sequence. At the estimated age of 249 million years, it is spinning rapidly with a projected rotational velocity of 235 km/s. This is giving the star an oblate shape with an equatorial bulge that is an estimated 18% larger than the polar radius. The star displays an infrared excess, suggesting the presence of a circumstellar disk of orbiting dust.

Epsilon Gruis is suspected of having a moderately active close companion, which is most likely the source of the weak X-ray emission from these coordinates with a luminosity of 1.3×10 erg s.

References

1. ^ van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. ^ Høg, E.; et al. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy and Astrophysics, 355: L27, Bibcode:2000A&A...355L..27H, doi:10.1888/0333750888/2862, ISBN 978-0333750889.
3. ^ Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992.
4. ^ 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.
5. ^ Ammler-von Eiff, Matthias; Reiners, Ansgar (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, S2CID 53666672.
6. ^ David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
7. "eps Gru". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-09-22.
8. Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2, S2CID 119273474.
9. Ertel, S.; et al. (October 2014), "A near-infrared interferometric survey of debris-disk stars. IV. An unbiased sample of 92 southern stars observed in H band with VLTI/PIONIER", Astronomy & Astrophysics, 570: 20, arXiv:1409.6143, Bibcode:2014A&A...570A.128E, doi:10.1051/0004-6361/201424438, S2CID 9594917, A128.
10. ^ Schröder, C.; et al. (June 2008), "Magnetic fields in A-type stars associated with X-ray emission", Astronomy and Astrophysics, 484 (2): 479–486, Bibcode:2008A&A...484..479S, doi:10.1051/0004-6361:20078963.
11. 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.

v t e Constellation of Grus
List of stars in Grus List of star names in Grus Grus in Chinese astronomy
Stars	Bayer α (Alnair) β (Tiaki) γ (Aldhanab) δ δ ε ζ η θ ι κ λ μ μ ν ξ ο π π ρ σ σ τ τ τ υ φ Variable RZ CE HR 8323 8501 HD 208487 (Itonda) 213240 215456 Other 2MASS J22282889–4310262 Gliese 832 PSR J2144−3933 S5-HVS1 WASP-95 WISE 2220−3628
Exoplanets Gliese 832 b HD 208487 b HD 213240 b τ Gruis b
Galaxies	NGC 7070 7070A 7072 7075 7079 7087 7213 7418 7424 7496 7531 7552 7582 7590 Other IC 1459 IC 5201
Galaxy clusters Abell S1063
Category

• A-type subgiants
• Circumstellar disks
• Grus (constellation)
• Bayer objects
• Durchmusterung objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects