2 Andromedae

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2 Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  23h 02m 36.38176s[1]
Declination +42° 45′ 28.0628″[1]
Apparent magnitude (V) 5.09[2] (5.26 + 7.43)[3]
2 And A
Spectral type A1V[4]
U−B color index +0.10[5]
B−V color index +0.08[5]
2 And B
Spectral type F1V/F4V[3]
Variable type δ Sct?[3]
2 And A
Radial velocity (Rv)2.1±2.4[6] km/s
Proper motion (μ) RA: 56.38[1] mas/yr
Dec.: −4.47[1] mas/yr
Parallax (π)7.74 ± 0.51[1] mas
Distance420 ± 30 ly
(129 ± 9 pc)
Absolute magnitude (MV)−0.39±0.16[7]
2 And B
Absolute magnitude (MV)1.88±0.16[7]
Period (P)73.997±0.509 yr
Semi-major axis (a)0.225±0.011
Eccentricity (e)0.800±0.056
Inclination (i)21.7±46.0°
Longitude of the node (Ω)159.5±2.0°
Periastron epoch (T)1870.280±0.595
Argument of periastron (ω)
2 And A
Mass2.7±0.1[7] M
Luminosity130.50[2] L
Surface gravity (log g)3.40±0.12[7] cgs
Temperature8,950±250[7] K
Rotational velocity (v sin i)212[8] km/s
[9] Myr
2 And B
Mass1.78±0.06[7] M
Surface gravity (log g)3.90±0.16[7] cgs
Temperature7,720±250[7] K
Other designations
BD+41° 4665, GJ 886.1, HD 217782, HIP 113788, HR 8766, SAO 52623, WDS 23026+4245[10]
Database references
2 And A
2 And B

2 Andromedae, abbreviated 2 And, is a binary star[3] system in the northern constellation of Andromeda. 2 Andromedae is the Flamsteed designation. It is a faint star system but visible to the naked eye with a combined apparent visual magnitude of 5.09.[2] Based upon an annual parallax shift of 7.7 mas,[1] it is located 420 light years away. The binary nature of the star was discovered by American astronomer Sherburne Wesley Burnham at Lick Observatory in 1889.[11] The pair orbit each other over a period of 74 years with a high eccentricity of 0.8.[3]

The magnitude 5.26[3] primary, designated component A, is an A-type main-sequence star based on a stellar classification of A1V[4] or A2V,[3] although it may have already left the main sequence.[7] It was identified as a candidate Lambda Boötis star, but this was ruled out by Paunzen et al. (2003) as it doesn't match the typical characteristics of these objects.[12] Although 2 And does not display a significant infrared excess, it is a shell star that displays varying absorption features due to circumstellar dust grains. This may indicate it has an orbiting debris disk containing gas that is being viewed edge-on.[13] The star is about 100 million years old and is spinning rapidly with a projected rotational velocity of 212 km/s.[8]

The magnitude 7.43[3] secondary companion, component B, is a suspected variable star and may be a Delta Scuti variable.[3] Alternatively, it may be an ellipsoidal variable with a brown dwarf companion.[7] It is an F-type main-sequence star with a class of F1V/F4.[3]


  1. ^ a b c d e f 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.Vizier catalog entry
  2. ^ a b c 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.
  3. ^ a b c d e f g h i j k Rica Romero, F. M. (2010). "Orbital elements for eight binaries. Study of the nature of wide components. I" (PDF). Revista Mexicana de Astronomía y Astrofísica. 46: 263–277. Bibcode:2010RMxAA..46..263R.
  4. ^ a b Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". The Astrophysical Journal Supplement Series. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182.
  5. ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Bibcode:1986EgUBV........0M.
  6. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  7. ^ a b c d e f g h i j Jerzykiewicz, M.; et al. (2015). "The 2003–2004 multisite photometric campaign for the β Cephei and eclipsing star 16 (EN) Lacertae with an appendix on 2 Andromedae, the variable comparison star". Monthly Notices of the Royal Astronomical Society. 454 (1): 724–740. arXiv:1508.05250. Bibcode:2015MNRAS.454..724J. doi:10.1093/mnras/stv1958.
  8. ^ a b Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691.
  9. ^ Gullikson, Kevin; et al. (August 2016). "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars". The Astronomical Journal. 152 (2): 13. arXiv:1604.06456. Bibcode:2016AJ....152...40G. doi:10.3847/0004-6256/152/2/40. 40.
  10. ^ "2 And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 11, 2018.
  11. ^ Burnham, S. W. (1894). "Sixteenth Catalogue of New Double Stars Discovered at the Lick Observatory". Publications of Lick Observatory. 2: 197–205. Bibcode:1894PLicO...2..197B.
  12. ^ Paunzen, E.; et al. (June 2003). "A study of lambda Bootis type stars in the wavelength region beyond 7000 Å". Astronomy and Astrophysics. 404: 579–591. Bibcode:2003A&A...404..579P. doi:10.1051/0004-6361:20030284.
  13. ^ Roberge, Aki; Weinberger, Alycia J. (March 2008). "Debris Disks around Nearby Stars with Circumstellar Gas". The Astrophysical Journal. 676 (1): 509–517. arXiv:0711.4561. Bibcode:2008ApJ...676..509R. doi:10.1086/527314.

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