28 Andromedae

28 Andromedae (abbreviated 28 And) is a Delta Scuti variable star in the constellation Andromeda. 28 Andromedae is the Flamsteed designation. It also bears the variable star name GN Andromedae. Its apparent magnitude is 5.214, varying by less than 0.1 magnitudes.

28 Andromedae

Location of 28 Andromedae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Andromeda
Right ascension	00h 30m 07.36s[1]
Declination	+29° 45′ 05.6″[1]
Apparent magnitude (V)	5.214[2]
Characteristics
Spectral type	A7 III[3]
U−B color index	+0.08[4]
B−V color index	+0.26[4]
Variable type	δ Sct[5]
Astrometry
Radial velocity (Rv)	−10.3±0.6[6] km/s
Proper motion (μ)	RA: 44.983±0.344[7] mas/yr Dec.: 55.668±0.176[7] mas/yr
Parallax (π)	16.3540±0.1743 mas[7]
Distance	199 ± 2 ly (61.1 ± 0.7 pc)
Absolute magnitude (MV)	1.29[8]
Details
Mass	1.77[9] M☉
Radius	3.19[7] R☉
Luminosity	25.007[7] L☉
Surface gravity (log g)	3.95±0.06[10] cgs
Temperature	7,335±69[10] K
Metallicity [Fe/H]	−0.09±0.05[10] dex
Rotational velocity (v sin i)	21±2[11] km/s
Age	1.159[9] Gyr
Other designations
BD+28°75, HD 2628, HIP 2355, HR 114, SAO 74041, PPM 89834
Database references
SIMBAD	data

Description

28 Andromedae is an A-type giant star,^[3] meaning it is colored bluish-white. Parallax estimates made by the Hipparcos spacecraft put the star at a distance of about 199 light years (61 parsecs).^[1] It is moving towards the solar system at a velocity of 10.30 km/s.^[6]

Multiplicity of the system

The blue band light curve, normalized to zero mean, of 28 Andromedae, adapted from Garrido et al.^[12]

Two stars near 28 Andromedae share a common proper motion with the primary star, which is then a candidate triple system. The orbital parameters are currently unknown. The second and third component have masses of 0.71 M_☉ and 0.14 M_☉ respectively.^[13]

Variability cycle

28 Andromedae A is a Delta Scuti variable, so it displays small luminosity variations at timescales less than a day due to star pulsation. There is evidence for two periodic cycles of 5,014 and 5,900 seconds, respectively. The amplitude variations, though, are not constant in time, and the pulsation modes are not radial.^[14]