Gamma Arae (
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Ara |
Right ascension | 17h 25m 23.65931s[1] |
Declination | –56° 22′ 39.8148″[1] |
Apparent magnitude (V) | 3.34[2] |
Characteristics | |
Spectral type | B1 Ib[3] |
U−B color index | –0.96[2] |
B−V color index | –0.13[2] |
Astrometry | |
Radial velocity (Rv) | –3[4] km/s |
Proper motion ( | RA: –0.44[1] mas/yr Dec.: –15.77[1] mas/yr |
Parallax ( | 2.93 ± 0.16 mas[1] |
Distance | 1,110 ± 60 ly (340 ± 20 pc) |
Absolute magnitude (MV) | –5.8[5] |
Details | |
Mass | 12.5[6]–25[5] M☉ |
Radius | 23[7] R☉ |
Luminosity | 120,000[5] L☉ |
Surface gravity (log g) | 2.90[8] cgs |
Temperature | 21,500[8] K |
Rotation | 4.8[9] |
Rotational velocity (v sin i) | 269 ± 11[8] km/s |
Age | 15.7 ± 0.1[6] Myr |
Other designations | |
Database references | |
SIMBAD | data |
This is an enormous star with 23[7] times the radius of the Sun. It is radiating 120,000[5] as much energy as the Sun from its outer envelope at an effective temperature of 21,500 K.[8] This heat gives the star the blue-white glow of a B-type star. The spectrum shows it to match a stellar classification of B1 Ib,[3] with the luminosity class of 'Ib' indicating this is a lower luminosity supergiant star.[10] It is a relatively young body, with an estimated age of around 15.7 million years.[6]
Gamma Arae is rotating rapidly with a projected rotational velocity of 269 km s−1, causing it to complete a full rotation about every 4.8 days.[9] In the spectrum of this star, this high rate of spin is causing absorption lines to blend together because of the Doppler effect, making them more difficult to analyze.[5] It is a periodically variable star that undergoes non-radial pulsations with a primary period of 1.1811 days and a secondary period of 0.1281 days.[8]
There is some disagreement about the mass of this star in the literature. Tetzlaff et al. (2011) estimate the mass as 12.5 ± 0.6[6] solar masses, while Fraser et al. (2010) give a mass of around 19[8] and Lefever et al. (2007) lists a value of 25.[5] It is shedding mass through its stellar wind at the rate of 3.0 × 10−8 solar masses per year, which is equivalent to losing the mass of the Sun every 33 million years.[8] The wind is being affected by the star's rapid rotation, resulting in an enhanced outflow along the equator.[7]
Gamma Arae has an optical companion located at an angular separation of 17.9 arcseconds, which is an A-type main sequence star with an apparent magnitude of 10.5.
References
edit- ^ a b c d e 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
- ^ a b c d Nicolet, B. (1978). "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System". Astronomy and Astrophysics Supplement Series. 34: 1–49. Bibcode:1978A&AS...34....1N.
- ^ a b Prinja, R. K.; Massa, D. L. (October 2010), "Signature of wide-spread clumping in B supergiant winds", Astronomy and Astrophysics, 521: L55, arXiv:1007.2744, Bibcode:2010A&A...521L..55P, doi:10.1051/0004-6361/201015252, S2CID 59151633
- ^ 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 I
AU Symposium no. 30, vol. 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E - ^ a b c d e f Lefever, K.; Puls, J.; Aerts, C. (March 2007), "Statistical properties of a sample of periodically variable B-type supergiants. Evidence for opacity-driven gravity-mode oscillations", Astronomy and Astrophysics, 463 (3): 1093–1109, arXiv:astro-ph/0611484, Bibcode:2007A&A...463.1093L, doi:10.1051/0004-6361:20066038, S2CID 8783008
- ^ a b c d 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
- ^ a b c Prinja, R. K.; et al. (February 1997), "Wind variability of B supergiants. II. The two-component stellar wind of
γ Arae", Astronomy and Astrophysics, 318: 157–170, Bibcode:1997A&A...318..157P - ^ a b c d e f g Fraser, M.; Dufton, P. L.; Hunter, I.; Ryans, R. S. I. (May 2010), "Atmospheric parameters and rotational velocities for a sample of Galactic B-type supergiants", Monthly Notices of the Royal Astronomical Society, 404 (3): 1306–1320, arXiv:1001.3337, Bibcode:2010MNRAS.404.1306F, doi:10.1111/j.1365-2966.2010.16392.x, S2CID 118674151
- ^ a b Prinja, R. K.; Massa, D.; Fullerton, A. W. (June 2002), "Wind variability of B supergiants. IV. A survey of IUE time-series data of 11 B0 to B3 stars", Astronomy and Astrophysics, 388 (2): 587–608, Bibcode:2002A&A...388..587P, doi:10.1051/0004-6361:20020503, hdl:2060/19970011906
- ^ "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