Astronomy:Alpha Circini

From HandWiki
Short description: Star in the constellation Circinus
α Circini
Circinus constellation map.svg
Red circle.svg
Location of α Circini (circled)
Observation data
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[1] mas
Distance54.0 ± 0.1 ly
(16.57 ± 0.04 pc)
Absolute magnitude (MV)+2.18[6]
Details
Mass1.5–1.7[7] M☉
Radius1.967 ± 0.066[8] R☉
Luminosity10.51 ± 0.60[7] L☉
Surface gravity (log g)4.1[7] cgs
Temperature7,500[7] K
Metallicity [Fe/H]0.13[9] dex
Rotation4.4790 ± 0.0001 days[10]
Rotational velocity (v sin i)13.0 ± 1.5[10] km/s
Age~12 million[11] years
Other designations
17. G Circini,[12] CD−64° 86, HD 128898, HIP 71908, HR 5463, SAO 252853.[13]
Database references
SIMBADdata

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]

A light curve for Alpha Circini, adapted from Bruntt et al. (2009)[10]

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

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V 
  2. ↑ 2.0 2.1 Samus, N. N. 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. 
  3. ↑ 3.0 3.1 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, doi:10.1086/504637, Bibcode: 2006AJ....132..161G 
  4. ↑ 4.0 4.1 4.2 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 
  5. ↑ 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 (University of Toronto: International Astronomical Union) 30: 57, Bibcode: 1967IAUS...30...57E 
  6. ↑ 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, doi:10.1051/0004-6361/201118724, Bibcode: 2012A&A...542A.116A. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 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, doi:10.1051/0004-6361/200911653, Bibcode: 2009A&A...499..851K 
  8. ↑ 8.0 8.1 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, doi:10.1111/j.1365-2966.2008.13167.x, Bibcode: 2008MNRAS.386.2039B 
  9. ↑ 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 
  10. ↑ 10.0 10.1 10.2 10.3 10.4 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, doi:10.1111/j.1365-2966.2009.14804.x, Bibcode: 2009MNRAS.396.1189B 
  11. ↑ 11.0 11.1 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, doi:10.1088/0004-6256/140/3/713, Bibcode: 2010AJ....140..713N 
  12. ↑ Gould, Benjamin Apthorp (1879), "Uranometria Argentina", Resultados del Observatorio Nacional Argentino en Cordoba (Buenos Aires) 1: 385, Bibcode: 1879RNAO....1.....G.  See VizieR catalogue V/135A.
  13. ↑ "* alf Cir". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+alf+Cir. 
  14. ↑ Kaler, James B., "ALPHA CIR (Alpha Circini)", Stars (University of Illinois), http://stars.astro.illinois.edu/sow/alphacir.html, retrieved 2012-01-04 
  15. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-01-16 



Retrieved from "https://handwiki.org/wiki/index.php?title=Astronomy:Alpha_Circini&oldid=3427059"