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.^[3] It is a red giant star with a spectral classification of K1III.

OP Andromedae

The visual band light curve of OP Andromedae, adapted from Barksdale et al. (1984) [1]
Observation data Epoch J2000      Equinox J2000
Constellation	Andromeda
Right ascension	01h 36m 27.1998s[2]
Declination	+48° 43′ 21.9998″}[2]
Apparent magnitude (V)	6.27 - 6.41[3]
Characteristics
Spectral type	K1III[3]
Apparent magnitude (J)	3.794[4]
Apparent magnitude (H)	3.165[4]
Apparent magnitude (K)	2.914[4]
B−V color index	1.2478[5]
Variable type	RS CVn[3]
Astrometry
Radial velocity (Rv)	−42.12±0.14[2] km/s
Proper motion (μ)	RA: −15.189±0.153[2] mas/yr Dec.: −17.663±0.148[2] mas/yr
Parallax (π)	6.3462±0.0912 mas[2]
Distance	514 ± 7 ly (158 ± 2 pc)
Absolute magnitude (MV)	0.37 ± 0.23[6]
Details
Mass	1.5 – 3[7] M☉
Radius	16.1±2.2[6] R☉
Luminosity	128.825[7] L☉
Surface gravity (log g)	2.14[7] cgs
Temperature	4,490[7] K
Metallicity [Fe/H]	-0.10[7] dex
Rotational velocity (v sin i)	7.2[7] km/s
Other designations
2MASS J01362720+4843221, BD+47° 460, HD 9746, HIP 7493, SAO 37351, PPM 44205, HR 454, TYC 3282-2270-1
Database references
SIMBAD	data

OP Andromedae is one of the few red giant stars where it was detected an overabundance of ⁷Li.^[6] 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.^[7]