R Muscae

R Muscae is a yellow-white hued variable star in the southern constellation of Musca. It has a nominal apparent visual magnitude of 6.31,^[5] which is near the lower limit of visibility to the naked eye. The distance to this star, as determined from its annual parallax shift of 1.00 mas,^[2] is around 3,260 light years.

R Muscae

Hubble Space Telescope image of R Muscae [1]
Observation data Epoch J2000      Equinox J2000
Constellation	Musca
Right ascension	12h 42m 05.02561s[2]
Declination	−69° 24′ 27.1966″[2]
Apparent magnitude (V)	5.93 - 6.73[3]
Characteristics
Spectral type	F7 Ib[4] - G2[3]
B−V color index	0.750±0.020[5]
Variable type	δ Cep[3]
Astrometry
Radial velocity (Rv)	+3.8±2.9[6] km/s
Proper motion (μ)	RA: −4.180[2] mas/yr Dec.: −2.127[2] mas/yr
Parallax (π)	1.0002±0.0291 mas[2]
Distance	3,260 ± 90 ly (1,000 ± 30 pc)
Absolute magnitude (MV)	-3.62[7]
Details
Radius	65[2] R☉
Luminosity	2,541[2] L☉
Surface gravity (log g)	2.0±0.1[8] cgs
Temperature	5,985±54[7] K
Metallicity [Fe/H]	+0.10±0.05[8] dex
Other designations
R Mus, AAVSO 1236-68, CD−68°1119, HD 110311, HIP 61981, HR 4820, SAO 251996[9]
Database references
SIMBAD	data

This is an F-type supergiant star with a baseline stellar classification of F7 Ib.^[4] It is a Classical Cepheid variable ranging from apparent magnitude 5.93 to 6.73^[10] over 7.51 days,^[7] while varying between spectral types F7 Ib and G2.^[10] The star was suspected of having a detectable companion,^[11] but this finding was later disputed.^[12] Gaia and HST observations have shown that there is a companion, a 15th-magnitude star 7″ away.^[13][14] There is an X-ray source with a luminosity of 6.3×10²⁹ erg s⁻¹ located at an angular separation of 1.9″ from R Muscae.^[15]

A light curve for R Muscae, plotted from TESS data