Astronomy:Eta2 Coronae Australis
  | |
| Observation data Epoch J2000.0 Equinox (celestial coordinates) | |
|---|---|
| Constellation | Corona Australis |
| Right ascension | 18h 49m 34.99649s[1] |
| Declination | −43° 26′ 02.7522″[1] |
| Apparent magnitude (V) | 5.59±0.01[2] |
| Characteristics | |
| Evolutionary stage | main sequence star[3] |
| Spectral type | B9 IV[4] |
| B−V color index | −0.08[5] |
| Astrometry | |
| Radial velocity (Rv) | −23.0±4.3[6] km/s |
| Proper motion (μ) | RA: −2.963[1] mas/yr Dec.: −25.374[1] mas/yr |
| Parallax (π) | 4.25 ± 0.1158[1] mas |
| Distance | 770 ± 20 ly (235 ± 6 pc) |
| Absolute magnitude (MV) | −0.24[7] |
| Details | |
| Mass | 3.23±0.08[3] M☉ |
| Radius | 5.82±0.31[8] R☉ |
| Luminosity | 171+20−18[3] L☉ |
| Surface gravity (log g) | 3.47[9] cgs |
| Temperature | 10,940±255[3] K |
| Metallicity [Fe/H] | +0.06[9] dex |
| Rotational velocity (v sin i) | 30[10] km/s |
| Age | 213[11] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Eta2 Coronae Australis (Eta2 CrA), Latinized from η2 Coronae Australis, is a solitary star[13] located in the southern constellation of Corona Australis. It is visible to the naked eye as a dim, blue-white hued star with an apparent visual magnitude of 5.59.[2] Gaia DR3 parallax measurements imply a distance of 770 light years from the Solar System,[1] but it is drifting closer with a radial velocity of −23 km/s.[6] At its current distance Eta2 CrA's brightness is diminished by 0.27 magnitudes due to stellar extinction from interstellar dust[14] and it has an absolute magnitude of −0.24.[7]
This object has a stellar classification of B9 IV,[4] indicating that is a slightly evolved a B-type subgiant star. However, Zorec & Royer (2012) model it to be a dwarf star that has completed 80.4% of its main sequence lifetime.[3] It is estimated to be 213 million years old[11] and it has a mass that is 3.23 times that of the Sun.[3] The star is radiating 171 times the luminosity of the Sun[3] from its photosphere 5.82 times the radius of the Sun[8] at an effective temperature of 10,940 K.[3] Eta2 CrA has a near-solar metallicity at [Fe/H] = +0.06[9] and spins modestly with a projected rotational velocity of 30 km/s.[10] Some earlier catalogues listed the object as a chemically peculiar star but that status is now considered to be doubtful.[15]
Sources
- ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 2.0 2.1 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Zorec, J.; Royer, F. (January 2012). "Rotational velocities of A-type stars IV: Evolution of rotational velocities". Astronomy & Astrophysics 537: A120. doi:10.1051/0004-6361/201117691. ISSN 0004-6361. Bibcode: 2012A&A...537A.120Z.
- ↑ 4.0 4.1 Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars: Declinations −53° to −40°. 2. Bibcode: 1978mcts.book.....H.
- ↑ Corben, P. M.; Stoy, R. H. (1968). "Photoelectric Magnitudes and Colours for Bright Southern Stars". Monthly Notes of the Astronomical Society of Southern Africa 27: 11. Bibcode: 1968MNSSA..27...11C.
- ↑ 6.0 6.1 Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35,495 Hipparcos stars in a common system". Astronomy Letters 32 (11): 759–771. doi:10.1134/S1063773706110065. ISSN 1063-7737. Bibcode: 2006AstL...32..759G.
- ↑ 7.0 7.1 Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode: 2012AstL...38..331A.
- ↑ 8.0 8.1 Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants. Surface brightness relations calibrated by interferometry". Astronomy & Astrophysics 426 (1): 297–307. doi:10.1051/0004-6361:20035930. ISSN 0004-6361. Bibcode: 2004A&A...426..297K.
- ↑ 9.0 9.1 9.2 Anders, F. et al. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics 628: A94. doi:10.1051/0004-6361/201935765. ISSN 0004-6361. Bibcode: 2019A&A...628A..94A.
- ↑ 10.0 10.1 Levato, Hugo; Grosso, Mónica (June 2004). "New Projected Rotational Velocities of All Southern B-type Stars of the Bright Star Catalogue". Symposium - International Astronomical Union 215: 51–52. doi:10.1017/S0074180900195191. ISSN 0074-1809. Bibcode: 2004IAUS..215...51L.
- ↑ 11.0 11.1 Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters 38 (11): 694–706, doi:10.1134/S1063773712110035, Bibcode: 2012AstL...38..694G.
- ↑ "Eta02 CrA". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Eta02+CrA.
- ↑ Eggleton, P. P.; Tokovinin, A. A. (11 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. ISSN 0035-8711. Bibcode: 2008MNRAS.389..869E.
- ↑ Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society 472 (4): 3805–3820. doi:10.1093/mnras/stx2219. ISSN 0035-8711. Bibcode: 2017MNRAS.472.3805G.
- ↑ Renson, P.; Manfroid, J. (19 March 2009). "Catalogue of Ap, HgMn and Am stars". Astronomy & Astrophysics 498 (3): 961–966. doi:10.1051/0004-6361/200810788. ISSN 0004-6361. Bibcode: 2009A&A...498..961R.
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