Astronomy:2 Andromedae

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Short description: Binary star system in the constellation Andromeda
Not to be confused with Andromeda II.
2 Andromedae
Location of 2 Andromedae (circled)
Observation data
Equinox J2000.0]] (ICRS)
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
2 And, BD+41°4665, GJ 886.1, HD 217782, HIP 113788, HR 8766, SAO 52623, PPM 63742, WDS 23026+4245[10]
Database references
SIMBAD2 And
2 And A
2 And B
A light curve for 2 Andromedae, plotted from TESS data[11]

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.[12] 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.[13] Although 2 Andromedae 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.[14] 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. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (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. http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2007A%2526A...474..653VFUL. Vizier catalog entry
  2. ↑ 2.0 2.1 2.2 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A. 
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 Rica Romero, F. M. (2010). "Orbital elements for eight binaries. Study of the nature of wide components. I". Revista Mexicana de Astronomía y Astrofísica 46: 263–277. Bibcode: 2010RMxAA..46..263R. http://www.astroscu.unam.mx/rmaa/RMxAA..46-2/PDF/RMxAA..46-2_frica.pdf. Retrieved 2014-09-01. 
  4. ↑ 4.0 4.1 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. doi:10.1086/192182. Bibcode: 1995ApJS...99..135A. 
  5. ↑ 5.0 5.1 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. doi:10.1134/S1063773706110065. Bibcode: 2006AstL...32..759G. 
  7. ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 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. doi:10.1093/mnras/stv1958. Bibcode: 2015MNRAS.454..724J. 
  8. ↑ 8.0 8.1 Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy & Astrophysics 537: A120. doi:10.1051/0004-6361/201117691. Bibcode: 2012A&A...537A.120Z. 
  9. ↑ Gullikson, Kevin et al. (August 2016). "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars". The Astronomical Journal 152 (2): 13. doi:10.3847/0004-6256/152/2/40. 40. Bibcode: 2016AJ....152...40G. 
  10. ↑ "2 And". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=2+And. 
  11. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. 
  12. ↑ 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. 
  13. ↑ Paunzen, E. et al. (June 2003). "A study of lambda Bootis type stars in the wavelength region beyond 7000 Å". Astronomy and Astrophysics 404 (2): 579–591. doi:10.1051/0004-6361:20030284. Bibcode: 2003A&A...404..579P. 
  14. ↑ Roberge, Aki; Weinberger, Alycia J. (March 2008). "Debris Disks around Nearby Stars with Circumstellar Gas". The Astrophysical Journal 676 (1): 509–517. doi:10.1086/527314. Bibcode: 2008ApJ...676..509R. 



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