Alpha Circini
Alpha Circini (α Cir, α Circini) is a variable star in the faint, southern, circumpolar constellation of Circinus. At an apparent visual magnitude of 3.19,[4] it is the brightest star in the constellation and can be readily seen with the naked eye from the southern hemisphere to as far north as 25° north latitude. Parallax measurements of this star yield an estimated distance of 54.0 light-years (16.6 parsecs) from the Earth.[1]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Circinus |
| Right ascension | 14h 42m 30.41958s[1] |
| Declination | −64° 58′ 30.4934″[1] |
| Apparent magnitude (V) | 3.18 - 3.21[2] |
| Characteristics | |
| Spectral type | A7 Vp SrCrEu[3] |
| U−B color index | +0.12[4] |
| B−V color index | +0.24[4] |
| Variable type | roAp[2] |
| Astrometry | |
| Radial velocity (Rv) | +7.2[5] km/s |
| Proper motion (μ) | RA: −192.53[1] mas/yr Dec.: −233.51[1] mas/yr |
| Parallax (π) | 60.35 ± 0.14 mas[1] |
| Distance | 54.0 ± 0.1 ly (16.57 ± 0.04 pc) |
| Absolute magnitude (MV) | +2.18[6] |
| Details | |
| Mass | 1.5–1.7[7] M☉ |
| Radius | 1.967 ± 0.066[8] R☉ |
| Luminosity | 10.51 ± 0.60[7] L☉ |
| Surface gravity (log g) | 4.1[7] cgs |
| Temperature | 7,500[7] K |
| Metallicity [Fe/H] | 0.13[9] dex |
| Rotation | 4.4790 ± 0.0001 days[10] |
| Rotational velocity (v sin i) | 13.0 ± 1.5[10] km/s |
| Age | ~12 million[11] years |
| Other designations | |
| Database references | |
| SIMBAD | data |
This star belongs to a class of variables known as rapidly oscillating Ap stars. It oscillates with multiple, non-radial pulsation cycles and a dominant cycle of 6.8 minutes.[10] The spectrum shows peculiar features caused by chemical stratification of the outer atmosphere. It displays a moderate deficiency of carbon, nitrogen and oxygen, while there is an overabundance of chromium (Cr).[7] The stellar classification of A7 Vp SrCrEu[3] indicates that this is a main sequence star with enhanced levels of strontium (Sr), chromium, and europium (Eu) in its atmosphere (compared to a typical star like the Sun).[14]
The mass of Alpha Circini is about 150% to 170% the mass of the Sun[7] and it has double the Sun's radius,[8] while the luminosity is more than 10 times that of the Sun. The effective temperature of the outer envelope is about 7,500 K, giving it the white hue typical of A-type stars.[7][15] It is rotating with a period of 4.5 days and the pole is inclined by about 37 ± 4° to the line of sight from the Earth.[10]
Based upon its location and motion through space, Alpha Circini is a candidate member of a stellar kinematic group known as the Beta Pictoris moving group. This group shares a common origin and has an estimated age of about 12 million years. At the birth of this group, Alpha Circini was estimated to be located at a distance of about 91 ly (28 pc) from the center of the assemblage.[11]
References edit
- ^ a b c d e f 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 Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
- ^ a b Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992
- ^ a b c Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
- ^ Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and Their Applications, Proceedings from IAU Symposium No. 30, 30, University of Toronto: International Astronomical Union: 57, Bibcode:1967IAUS...30...57E
- ^ 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, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, S2CID 53666672.
- ^ a b c d e f g Kochukhov, O.; Shulyak, D.; Ryabchikova, T. (June 2009), "A self-consistent empirical model atmosphere, abundance and stratification analysis of the benchmark roAp star α Circini", Astronomy and Astrophysics, 499 (3): 851–863, arXiv:0903.3512, Bibcode:2009A&A...499..851K, doi:10.1051/0004-6361/200911653, S2CID 17511410
- ^ a b Bruntt, H.; et al. (June 2008), "The fundamental parameters of the roAp star α Circini", Monthly Notices of the Royal Astronomical Society, 386 (4): 2039–2046, arXiv:0803.1518, Bibcode:2008MNRAS.386.2039B, doi:10.1111/j.1365-2966.2008.13167.x, S2CID 13859127
- ^ North, P.; Berthet, S.; Lanz, T. (January 1994), "The nature of the F STR lambda 4077 stars. 3: Spectroscopy of the barium dwarfs and other CP stars", Astronomy and Astrophysics, 281 (3): 775–796, Bibcode:1994A&A...281..775N
- ^ a b c d e Bruntt, H.; et al. (June 2009), "Asteroseismic analysis of the roAp star α Circini: 84d of high-precision photometry from the WIRE satellite", Monthly Notices of the Royal Astronomical Society, 396 (2): 1189–1201, arXiv:0903.3967, Bibcode:2009MNRAS.396.1189B, doi:10.1111/j.1365-2966.2009.14804.x, S2CID 119292022
- ^ a b Nakajima, Tadashi; Morino, Jun-Ichi; Fukagawa, Misato (September 2010), "Potential Members of Stellar Kinematical Groups within 20 pc of the Sun", The Astronomical Journal, 140 (3): 713–722, Bibcode:2010AJ....140..713N, doi:10.1088/0004-6256/140/3/713
- ^ Gould, Benjamin Apthorp (1879), "Uranometria Argentina", Resultados del Observatorio Nacional Argentino en Cordoba, 1, Buenos Aires: 385, Bibcode:1879RNAO....1.....G. See VizieR catalogue V/135A.
- ^ "* alf Cir". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-01-04.
- ^ Kaler, James B., "ALPHA CIR (Alpha Circini)", Stars, University of Illinois, retrieved 2012-01-04
- ^ , Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on February 22, 2012, retrieved 2012-01-16