104 Herculis

104 Herculis is a solitary^[11] variable star^[2] located around 560^[3] light years away from the Sun in the northern constellation of Hercules.^[9] It has the variable star designation V669 Herculis and the Bayer designation A Herculis, while 104 Herculis is the Flamsteed designation. This object is visible to the naked eye as a dim, red-hued point of light with a baseline apparent visual magnitude of 4.96.^[4] It is moving closer to the Earth with a heliocentric radial velocity of −1.2 km/s.^[4]

104 Herculis

A visual band light curve for V669 Herculis. The main plot shows the long-term variation (plotted from data published by Tabur et al.[1]) and the inset plot shows the short-term periodic variation (adapted from Adelman and William[2]).
Observation data Epoch J2000      Equinox J2000
Constellation	Hercules
Right ascension	18h 11m 54.15649s[3]
Declination	+31° 24′ 19.2469″[3]
Apparent magnitude (V)	4.96[4]
Characteristics
Evolutionary stage	AGB[5]
Spectral type	M3 III[6]
B−V color index	1.643±0.004[4]
Variable type	semiregular[7]
Astrometry
Radial velocity (Rv)	−1.19±0.29[4] km/s
Proper motion (μ)	RA: −15.172[3] mas/yr Dec.: +25.084[3] mas/yr
Parallax (π)	5.8167±0.1769 mas[3]
Distance	560 ± 20 ly (172 ± 5 pc)
Absolute magnitude (MV)	−1.15[4]
Details
Radius	85.80+6.65 −10.88[3] R☉
Luminosity	1,202.3±42.1[3] L☉
Surface gravity (log g)	0.99±0.29[8] cgs
Temperature	3,535±24[8] K
Metallicity [Fe/H]	−0.08±0.10[8] dex
Other designations
A Her, 104 Her, V669 Her, AAVSO 1808+31B, BD+31°3199, FK5 3448, HD 167006, HIP 89172, HR 6815, SAO 66737[9][10]
Database references
SIMBAD	data

The variability of the brightness of 104 Herculis was announced by Joel Stebbins and Charles Morse Huffer in 1928, based on observations made at Washburn Observatory.^[12] It was given its variable star designation in 1977.^[13]

This is an aging red giant star on the asymptotic giant branch^[5] with a stellar classification of M3 III.^[6] It is a semiregular variable^[7] with an amplitude of 0.14 in the B-band^[14] and pulsation periods of 22.9 and 24.0 days.^[1] Having exhausted the hydrogen at its core, the star has expanded to 86^[3] times the Sun's radius. It is radiating 1,202^[3] times the Sun's luminosity from its swollen photosphere at an effective temperature of 3,535 K.^[8]