Astronomy:Epsilon Gruis
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Grus |
| Right ascension | 22h 48m 33.29833s[1] |
| Declination | −51° 19′ 00.7001″[1] |
| Apparent magnitude (V) | 3.466[2] |
| Characteristics | |
| Spectral type | A2 IVn[3] |
| B−V color index | 0.09[2] |
| Astrometry | |
| Radial velocity (Rv) | −0.4±2.1[4] km/s |
| Proper motion (μ) | RA: +108.43[1] mas/yr Dec.: −64.83[1] mas/yr |
| Parallax (π) | 25.30 ± 0.48[1] mas |
| Distance | 129 ± 2 ly (39.5 ± 0.7 pc) |
| Absolute magnitude (MV) | +0.52[5] |
| Details | |
| Mass | 1.85[6] M☉ |
| Surface gravity (log g) | 3.47±0.14[6] cgs |
| Temperature | 8,685±295[6] K |
| Metallicity [Fe/H] | −0.16[3] dex |
| Rotational velocity (v sin i) | 235.1±11.8[5] km/s |
| Age | 249[6] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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.[2] Based upon an annual parallax shift of 25.30 mas as measured from Earth,[1] 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.[4]
This is an A-type subgiant of spectral type A2IVn,[3] 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,[6] it is spinning rapidly with a projected rotational velocity of 235 km/s.[5] This is giving the star an oblate shape with an equatorial bulge that is an estimated 18% larger than the polar radius.[8] The star displays an infrared excess, suggesting the presence of a circumstellar disk of orbiting dust.[9]
Epsilon Gruis is suspected of having a moderately active[10] close companion,[11] which is most likely the source of the weak X-ray emission from these coordinates with a luminosity of 1.3×1028 erg s−1.[10]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V.
- ↑ 2.0 2.1 2.2 Høg, E. et al. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy and Astrophysics 355: L27, doi:10.1888/0333750888/2862, ISBN 978-0333750889, Bibcode: 2000A&A...355L..27H.
- ↑ 3.0 3.1 3.2 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, doi:10.1086/504637, Bibcode: 2006AJ....132..161G.
- ↑ 4.0 4.1 Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G.
- ↑ 5.0 5.1 5.2 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, doi:10.1051/0004-6361/201118724, Bibcode: 2012A&A...542A.116A.
- ↑ 6.0 6.1 6.2 6.3 6.4 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, doi:10.1088/0004-637X/804/2/146, Bibcode: 2015ApJ...804..146D.
- ↑ "eps Gru". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=eps+Gru.
- ↑ Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review 20 (1): 51, doi:10.1007/s00159-012-0051-2, Bibcode: 2012A&ARv..20...51V.
- ↑ 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, doi:10.1051/0004-6361/201424438, A128, Bibcode: 2014A&A...570A.128E.
- ↑ 10.0 10.1 Schröder, C. et al. (June 2008), "Magnetic fields in A-type stars associated with X-ray emission", Astronomy and Astrophysics 484 (2): 479–486, doi:10.1051/0004-6361:20078963, Bibcode: 2008A&A...484..479S.
- ↑ 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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E.
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