Alpheratz

"21 Andromedae" redirects here. For the galaxy, see Andromeda XXI.

Alpheratz/α Andromedae
Location of Alpheratz in Andromeda (circled)
Location of Alpheratz in Pegasus (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Andromeda
Right ascension 00h 08m 23.25988s[1]
Declination +29° 05′ 25.5520″[1]
Apparent magnitude (V) 2.06 (2.22 + 4.21)[2]
Characteristics
U−B color index −0.46[3]
B−V color index −0.11[3]
R−I color index −0.10[3]
Primary
Spectral type B8IV-VHgMn[4]
B−V color index −0.06[5]
Secondary
Spectral type A7V[5]
B−V color index 0.22[5]
Astrometry
Primary
Radial velocity (Rv)−10.6 ± 0.3[a] km/s
Proper motion (μ) RA: 135.68[6] mas/yr
Dec.: −162.95[6] mas/yr
Parallax (π)33.62 ± 0.35 mas[1]
Distance97 ± 1 ly
(29.7 ± 0.3 pc)
Absolute magnitude (MV)−0.193[5][b]
Secondary
Absolute magnitude (MV)1.797[5]
Orbit
Period (P)96.69[7] days
Semi-major axis (a)23.917±0.127 mas[7]
(0.7146±0.0327 AU)[5]
Eccentricity (e)0.526±0.013[7]
Inclination (i)105.8±0.17[7]°
Longitude of the node (Ω)104.46±0.48[7]°
Periastron epoch (T)MJD 47374.563 ± 0.095[2]
Argument of periastron (ω)
(secondary)		257.4 ± 0.31[2]°
Details
Primary
Mass3.63±0.201[7] M☉
Radius2.94 ± 0.34[5][c] R☉
Luminosity (bolometric)158+41
−33[5] L☉
Surface gravity (log g)3.75[8] cgs
Temperature11,950[5] K
Rotation2.38 d[9]
Rotational velocity (v sin i)53[10] km/s
Age60;[8] 200+117
−74[5] Myr
Secondary
Mass1.875±0.096[7] M☉
Radius2.03 ± 0.23[5][d] R☉
Luminosity (bolometric)14.79+3.83
−3.04[5] L☉
Surface gravity (log g)4.0[8] cgs
Temperature7,935[5] K
Age70;[8] 447+184
−130[5] Myr
Other designations
Alpheratz, Sirrah, Sirah, α And, Alpha Andromedae, Alpha And, δ Pegasi, δ Peg, Delta Pegasi, Delta Peg, 21 Andromedae, 21 And, H 5 32A, MKT 11, ADS 94 A, BD+28°4, CCDM J00083+2905A, FK5 1, GC 127, HD 358, HIP 677, HR 15, IDS 00032+2832 A, LTT 10039, NLTT 346, PPM 89441, SAO 73765, WDS 00084+2905A/Aa[6][11][12]
Database references
SIMBADdata

Alpheratz /ælˈfɪəræts/,[13][14] or Alpha Andromedae (α Andromedae, abbreviated Alpha And or α And), is a binary star 97 light-years from Earth and is the brightest star in the constellation of Andromeda when Mirach (β Andromedae) undergoes its periodical dimming. Immediately northeast of the constellation of Pegasus, it is the upper left star of the Great Square of Pegasus.

Although it appears to the naked eye as a single star, with overall apparent visual magnitude +2.06, it is actually a binary system composed of two stars in close orbit. The chemical composition of the brighter of the two stars is unusual as it is a mercury-manganese star whose atmosphere contains abnormally high levels of mercury, manganese, and other elements, including gallium and xenon.[15] It is the brightest mercury-manganese star known.[15]

  1. ^ a b c Van Leeuwen, F. (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.
  2. ^ a b c Entry, WDS identifier 00084+2905, Sixth Catalog of Orbits of Visual Binary Stars Archived 2017-11-12 at the Wayback Machine, William I. Hartkopf & Brian D. Mason, U.S. Naval Observatory. Accessed on line August 12, 2008.
  3. ^ a b c Hoffleit, D.; Warren, W. H. Jr. "HR 15". The Bright Star Catalogue (5th Revised ed.). VizieR. and Hoffleit, D.; Warren, W. H. Jr. "Detailed Description of V/50". The Bright Star Catalogue (5th Revised ed.). Centre de Données astronomiques de Strasbourg.
  4. ^ Cite error: The named reference :0 was invoked but never defined (see the help page).
  5. ^ a b c d e f g h i j k l m n Piccotti, Luca; Docobo, José Ángel; Carini, Roberta; Tamazian, Vakhtang S.; Brocato, Enzo; Andrade, Manuel; Campo, Pedro P. (2020-02-01). "A study of the physical properties of SB2s with both the visual and spectroscopic orbits". Monthly Notices of the Royal Astronomical Society. 492 (2): 2709–2721. Bibcode:2020MNRAS.492.2709P. doi:10.1093/mnras/stz3616. ISSN 0035-8711. Alpha Andromedae's database entry at VizieR.
  6. ^ a b c "* alf And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved August 12, 2008.
  7. ^ a b c d e f g Branham Jr, Richard L. (2017-01-01). "A three-dimensional orbit for the binary star Alpha Andromedae". Monthly Notices of the Royal Astronomical Society. 464 (1): 1095–1101. Bibcode:2017MNRAS.464.1095B. doi:10.1093/mnras/stw2393. hdl:11336/64233. ISSN 0035-8711.
  8. ^ a b c d Ryabchikova, T.; Malanushenko, V.; Adelman, S. J. (1998). "The double-lined spectroscopic binary alpha Andromedae: Orbital elements and elemental abundances". Contributions of the Astronomical Observatory Skalnate Pleso. 27 (3): 356. arXiv:astro-ph/9805205. Bibcode:1998CoSka..27..356R.
  9. ^ Cite error: The named reference sciphys was invoked but never defined (see the help page).
  10. ^ David, Trevor J.; Hillenbrand, Lynne A. (2015-05-01). "The Ages of Early-type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146. ISSN 0004-637X. Alpheratz's database entry at VizieR.
  11. ^ Cite error: The named reference usno was invoked but never defined (see the help page).
  12. ^ Entry 00084+2905, discoverer code MKT  11, components Aa, The Washington Double Star Catalog Archived 2011-08-16 at the Wayback Machine, United States Naval Observatory. Accessed on line August 15, 2017.
  13. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  14. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  15. ^ a b Alpheratz, Kaler Stars [1] 2/14/2013


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