Epsilon Apodis

ε Apodis

Location of ε Apodis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Apus[1]
Right ascension	14^h 22^m 23.16467^s[2]
Declination	−80° 06′ 32.2053″[2]
Apparent magnitude (V)	5.06[3]
Characteristics
Spectral type	B3 V[4]
U−B color index	−0.610[3]
B−V color index	−0.121[3]
Variable type	γ Cas[5]
Astrometry
Radial velocity (Rv)	+4.5±4.2[6] km/s
Proper motion (μ)	RA: −9.51[2] mas/yr Dec.: −14.34[2] mas/yr
Parallax (π)	5.06±0.22 mas[2]
Distance	640 ± 30 ly (198 ± 9 pc)
Absolute magnitude (MV)	−1.41[1]
Details
Mass	6.15±0.71[7] M☉
Radius	4.30±0.09[8] R☉
Luminosity	1,614[7] L☉
Surface gravity (log g)	3.50±0.04[8] cgs
Temperature	17,100±171[8] K
Metallicity [Fe/H]	−0.02[9] dex
Rotational velocity (v sin i)	150±3[8] km/s
Age	38.3±4.4[10] Myr
Other designations
ε Aps, CD−79°559, HD 124771, HIP 70248, HR 5336, SAO 257142[11]
Database references
SIMBAD	data

Epsilon Apodis is a star in the southern circumpolar constellation of Apus. Its identifier is a Bayer designation that is Latinized from ε Apodis, and abbreviated Eps Aps or ε Aps, respectively. This star has an apparent visual magnitude of 5.06,^[3] which is bright enough to be viewed from dark suburban skies. Based upon parallax measurements, it is at a distance of roughly 640 light-years (200 parsecs) from Earth.^[2] The star is drifting further away with a heliocentric radial velocity of +4.5 km/s.^[6]

A light curve for Epsilon Apodis, plotted from Hipparcos data^[12]

Based upon a stellar classification of B3 V,^[4] this is a massive, B-type main sequence star that is generating energy through the fusion of hydrogen at its core. Epsilon Apodis has more than six^[7] times the mass of the Sun and over four^[8] times the Sun's radius. It is radiating 1,614^[7] times as much luminosity as the Sun from its photosphere at an effective temperature of 17,100 K.^[8] At this heat, it has a blue-white glow that is a characteristic of B-type stars.^[13]

Epsilon Apodis is spinning rapidly, with a projected rotational velocity of 150 km/s^[8] giving a lower bound for the azimuthal velocity along the equator. Epsilon Apodis is classified as a Gamma Cassiopeiae type^[5] variable star and its brightness varies between magnitudes 4.99 and 5.04.^[14]

Naming

In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 異雀 (Yì Què), meaning Exotic Bird, refers to an asterism consisting of ε Apodis, ζ Apodis, ι Apodis, β Apodis, γ Apodis, δ Octantis, δ¹ Apodis, η Apodis and α Apodis. Consequently, ε Apodis itself is known as 異雀九 (Yì Què jiǔ, English: the Ninth Star of Exotic Bird.)^[15]

References

1. 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.
2. van Leeuwen, F. (November 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.
3. Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168.
4. Houk, Nancy (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.
5. Kazarovets, E. V.; et al. (January 1999), "The 74th Special Name-list of Variable Stars", Information Bulletin on Variable Stars, 4659: 1, Bibcode:1999IBVS.4659....1K.
6. Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, vol. 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E.
7. Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355, S2CID 111387483.
8. Arcos, C.; et al. (March 2018), "Stellar parameters and H α line profile variability of Be stars in the BeSOS survey", Monthly Notices of the Royal Astronomical Society, 474 (4): 5287–5299, arXiv:1711.08675, Bibcode:2018MNRAS.474.5287A, doi:10.1093/mnras/stx3075.
9. Saffe, C.; et al. (October 2008), "Spectroscopic metallicities of Vega-like stars", Astronomy and Astrophysics, 490 (1): 297–305, arXiv:0805.3936, Bibcode:2008A&A...490..297S, doi:10.1051/0004-6361:200810260, S2CID 15059920.
10. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
11. "eps Aps -- Be Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-08.
12. "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
13. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16.
14. Samus, N. N.; Durlevich, O. V.; Kazarovets, R. V., "eps Aps", General Catalogue of Variable Stars, Sternberg Astronomical Institute, retrieved 2012-07-09.
15. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 29 日 Archived 2011-05-22 at the Wayback Machine

External links

• Simbad
• Image Epsilon Apodis