OP Andromedae

OP Andromedae is a variable star in the constellation Andromeda. Varying between magnitudes 6.27 and 6.41 over 2.36 days, it has been classified as an RS Canum Venaticorum variable, but there has not been any proof of binarity, yet.[2] It's a red giant star which spectral classification is K1III.

OP Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  01h 36m 27.1998s[1]
Declination +48° 43′ 21.9998″}[1]
Apparent magnitude (V) 6.27 - 6.41[2]
Characteristics
Spectral type K1III[2]
Apparent magnitude (J) 3.794[3]
Apparent magnitude (H) 3.165[3]
Apparent magnitude (K) 2.914[3]
B−V color index 1.2478[4]
Variable type RS CVn[2]
Astrometry
Radial velocity (Rv)−42.12±0.14[1] km/s
Proper motion (μ) RA: −15.189±0.153[1] mas/yr
Dec.: −17.663±0.148[1] mas/yr
Parallax (π)6.3462 ± 0.0912[1] mas
Distance514 ± 7 ly
(158 ± 2 pc)
Absolute magnitude (MV)0.37 ± 0.23[5]
Details
Mass1.5 – 3[6] M☉
Radius16.1±2.2[5] R☉
Luminosity128.825[6] L☉
Surface gravity (log g)2.14[6] cgs
Temperature4,490[6] K
Metallicity [Fe/H]-0.10[6] dex
Rotational velocity (v sin i)7.2[6] km/s
Other designations
2MASS J01362720+4843221, BD+47° 460, HD 9746, HIP 7493, SAO 37351, HR 454, TYC 3282-2270-1.
Database references
SIMBADdata

OP Andromedae is one of the few red giant stars where it was detected an overabundance of 7Li.[5] The mechanism that enhances lithium in red giants is still unknown. It was proposed that those stars engulfed planets in the recent past; however, this theory was discarded since there is an overabundance of just one lithium isotope.[6]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. N. N. Samus; O. V. Durlevich; et al. "OP And database entry". Combined General Catalog of Variable Stars (2017 ed.). CDS. Retrieved 2018-11-12.
  3. Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; et al. (June 2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues (2246): II/246. Bibcode:2003yCat.2246....0C.
  4. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy & Astrophysics, 355: L27–L30, Bibcode:2000A&A...355L..27H.
  5. Balachandran, Suchitra C.; Fekel, Francis C.; Henry, Gregory W.; Uitenbroek, Han (2000). "Two K Giants with Supermeteoritic Lithium Abundances: HDE 233517 and HD 9746". The Astrophysical Journal. 542 (2): 978–88. Bibcode:2000ApJ...542..978B. CiteSeerX 10.1.1.36.1062. doi:10.1086/317055.
  6. Takeda, Y.; Tajitsu, A. (August 2017). "On the observational characteristics of lithium-enhanced giant stars in comparison with normal red giants". Publications of the Astronomical Society of Japan. 69 (4): 978–88. arXiv:1706.02273. Bibcode:2017PASJ...69...74T. doi:10.1093/pasj/psx057.
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