2 Andromedae

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]

Not to be confused with Andromeda II.
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]
Characteristics
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]
Astrometry
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]
Orbit[3]
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)
(secondary)		356.4±3.0°
Details
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
Age100+309
−88[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
SIMBAD2 And
2 And A
2 And B

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]

References
  1. 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.Vizier catalog entry
  2. 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. S2CID 119257644.
  3. 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. 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. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. 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. S2CID 119231169.
  7. 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. S2CID 119220117.
  8. 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. S2CID 55586789.
  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. S2CID 119179065. 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. arXiv:astro-ph/0303191. 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. S2CID 18407657.
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