Epsilon Piscis Austrini
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Piscis Austrinus |
| Right ascension | 22h 40m 39.34826s[1] |
| Declination | −27° 02′ 37.0151″[1] |
| Apparent magnitude (V) | +4.17[2] |
| Characteristics | |
| Spectral type | B8 Ve[3] or B8 IVe[4] |
| U−B color index | −0.31[2] |
| B−V color index | −0.11[2] |
| Astrometry | |
| Radial velocity (Rv) | +1.1±2.8[5] km/s |
| Proper motion (μ) | RA: +21.839 mas/yr[1] Dec.: −1.588 mas/yr[1] |
| Parallax (π) | 5.9219±0.2931 mas[1] |
| Distance | 550 ± 30 ly (169 ± 8 pc) |
| Absolute magnitude (MV) | −1.66[4] |
| Details | |
| Mass | 5.95±0.30[6] M☉ |
| Radius | 7.51±0.38[6] R☉ |
| Luminosity | 661[7] L☉ |
| Surface gravity (log g) | 3.93[8] cgs |
| Temperature | 11,066[7] K |
| Rotational velocity (v sin i) | 216[7] km/s |
| Other designations | |
| ε PsA, 18 Piscis Austrini, CD−27°16010, FK5 854, HD 214748, HIP 111954, HR 8628, SAO 191318[9] | |
| Database references | |
| SIMBAD | data |
Epsilon Piscis Austrini, Latinized from ε Piscis Austrini, is a blue-white hued star in the southern constellation of Piscis Austrinus. It is visible to the naked eye with an apparent visual magnitude of +4.17.[2] Based upon an annual parallax shift of 5.92mas as seen from the Gaia satellite, the system is located at a distance of roughly 550 light years.[1]
Characteristics
[edit]This is a B-type main sequence star with a stellar classification of B8 Ve.[3] It is a Be star that is spinning rapidly with a projected rotational velocity of 216 km/s,[7] compared to an equatorial critical velocity of 301 km/s.[8] The star has 6.0 times the mass of the Sun, 7.5 times the Sun's radius,[6] and is radiating 661 times the solar luminosity from its photosphere at an effective temperature of 11,066 K.[7]
Epsilon Piscis Austrini is part of a wide binary star system, the companion is likely a low-mass red dwarf with a projected separation of 11,700 astronomical units. It also exhibits a strong discrepancy between proper motion measurements taken by the Hipparcos and Gaia satellites, hinting the presence of an astrometric companion, possibly a solar-mass star, with a separation between 6 and 30 au.[6]
The star is moving through the Galaxy at 18.7 km/s relative to the Sun. Its projected Galactic orbit carries it between 23,917 and 28,138 light-years from the center of the Galaxy.[10]
Naming
[edit]In Chinese, 羽林軍 (Yǔ Lín Jūn), meaning Palace Guard, refers to an asterism consisting of:
- ε Piscis Austrini
- 29 Aquarii
- 35 Aquarii
- 41 Aquarii
- 47 Aquarii
- 49 Aquarii
- λ Piscis Austrini
- HD 212448
- 21 Piscis Austrini
- 20 Piscis Austrini
- υ Aquarii
- 68 Aquarii
- 66 Aquarii
- 61 Aquarii
- 53 Aquarii
- 50 Aquarii
- 56 Aquarii
- 45 Aquarii
- 58 Aquarii
- 64 Aquarii
- 65 Aquarii
- 70 Aquarii
- 74 Aquarii
- τ2 Aquarii
- τ1 Aquarii
- δ Aquarii
- 77 Aquarii
- 88 Aquarii
- 89 Aquarii
- 86 Aquarii
- 101 Aquarii
- 100 Aquarii
- 99 Aquarii
- 98 Aquarii
- 97 Aquarii
- 94 Aquarii
- ψ3Aquarii
- ψ2Aquarii
- ψ1Aquarii
- 87 Aquarii
- 85 Aquarii
- 83 Aquarii
- χ Aquarii
- ω1 Aquarii
- ω2 Aquarii
Consequently, the Chinese name for ε Piscis Austrini itself is 羽林軍八 (Yǔ Lín Jūn bā, English: the Eighth Sixth Star of Palace Guard.)[11]
References
[edit]- ^ a b c d e 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 Feinstein, A.; Marraco, H. G. (November 1979), "The photometric behavior of Be Stars", Astronomical Journal, 84: 1713–1725, Bibcode:1979AJ.....84.1713F, doi:10.1086/112600.
- ^ a b Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
- ^ 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, S2CID 119257644.
- ^ 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.
- ^ a b c d Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (January 2022), "Stellar and substellar companions from Gaia EDR3. Proper-motion anomaly and resolved common proper-motion pairs", Astronomy and Astrophysics, 657: A7, arXiv:2109.10912, Bibcode:2022A&A...657A...7K, doi:10.1051/0004-6361/202142146, ISSN 0004-6361. Radius and mass are available only in the VizieR catalog.
- ^ a b c d e Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
- ^ a b Chauville, J.; et al. (November 2001), "High and intermediate-resolution spectroscopy of Be stars 4481 lines", Astronomy and Astrophysics, 378: 8618–82, Bibcode:2001A&A...378..861C, doi:10.1051/0004-6361:20011202, hdl:11336/36962.
- ^ "eps PsA -- Be Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-05-18.
- ^ 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, S2CID 119257644.
- ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 7 日 Archived 2011-05-21 at the Wayback Machine
