U Vulpeculae

U Vulpeculae is a variable and binary star in the constellation Vulpecula. It is not visible to the naked eye, but can be seen with binoculars.

U Vulpeculae

A visual band light curve for U Vulpeculae, adapted from Kiss (1998)[1]
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Vulpecula
Right ascension	19h 36m 37.7281s[2]
Declination	20° 19′ 58.5692″[2]
Apparent magnitude (V)	6.73 - 7.54[3]
Characteristics
Spectral type	F6Iab-G2[4]
Variable type	δ Cep[3]
Astrometry
Proper motion (μ)	RA: 0.906±0.050[2] mas/yr Dec.: −0.960±0.062[2] mas/yr
Parallax (π)	1.0530±0.0390 mas[2]
Distance	3,100 ± 100 ly (950 ± 40 pc)
Absolute magnitude (MV)	-3.69[5]
Orbit[6]
Period (P)	2,510 days
Eccentricity (e)	0.675
Periastron epoch (T)	2444800
Argument of periastron (ω) (secondary)	353°
Semi-amplitude (K1) (primary)	3.64 km/s
Details
Mass	6.5[7] M☉
Radius	60[7] R☉
Surface gravity (log g)	1.75 - 1.85[8] cgs
Temperature	5,655 - 5,965[8] K
Metallicity [Fe/H]	0.09[9] dex
Age	82[9] Myr
Other designations
BD+20° 4200, HD 185059, HIP 96458, HR 7458, SAO 87447[10]
Database references
SIMBAD	data

It is a classical Cepheid variable and its apparent magnitude ranges from 6.73 to 7.54 over a precise cycle of 7.99 days.^[4] Its variable nature was discovered in 1898 at Potsdam Observatory by Gustav Müller and Paul Kempf.^[11]

In 1991 a study of radial velocities showed that it U Vulpeculae is a spectroscopic binary and a full orbit with a period of 2510 days (6.9 years) was first calculated in 1996.^[12][7] The secondary star is invisible and is only known from its effect on the motion of the primary.^[6]