Eta Muscae

Eta Muscae is a multiple^[9][10] star system in the southern constellation of Musca. It is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude of 4.79.^[3] The system is located around 406 light years away from the Sun.^[6] It is a member of the Lower Centaurs Crux subgroup of the Sco OB2 stellar association of co-moving stars.^[11]

Eta Muscae

A light curve for Eta Muscae plotted from TESS data[1]
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Musca
Right ascension	13h 15m 14.94123s[2]
Declination	−67° 53′ 40.5276″[2]
Apparent magnitude (V)	4.79[3]
Characteristics
Spectral type	B8V + sim. + K9.4XR? + A0p[4] or B7III + B7III[5]
B−V color index	−0.078±0.003[3]
Variable type	eclipsing binary
Astrometry
Radial velocity (Rv)	−8.1±7.4[3] km/s
Proper motion (μ)	RA: +30.207[2] mas/yr Dec.: +17.921[2] mas/yr
Parallax (π)	7.1001±0.1924 mas[2]
Distance	405.7[6] ly (124.4[6] pc)
Absolute magnitude (MV)	−0.81[6]
Orbit[7]
Period (P)	2.3963161 d
Semi-major axis (a)	14.11±0.15 R☉
Eccentricity (e)	0.00
Inclination (i)	77.40°
Semi-amplitude (K1) (primary)	145.35±0.20 km/s
Semi-amplitude (K2) (secondary)	145.38±0.20 km/s
Details[7]
Eta Mus Aa
Mass	3.30±0.04 M☉
Radius	2.14±0.02 R☉
Luminosity	223.77[3] (combined) L☉
Surface gravity (log g)	4.293±0.005 cgs
Temperature	12,700±100 K
Rotational velocity (v sin i)	34±2 km/s
Eta Mus Ab
Mass	3.29±0.04 M☉
Radius	2.13±0.04 R☉
Surface gravity (log g)	4.298±0.005 cgs
Temperature	12,550±300 K
Rotational velocity (v sin i)	44±2 km/s
Other designations
η Mus, CPD−67°2224, FK5 493, HD 114911, HIP 64661, HR 4993, SAO 252224, WDS J13152-6754A[8]
Database references
SIMBAD	data

The two main components of this system form a double-lined spectroscopic binary^[12] with a period of 2.4 days in a circular orbit.^[7][11] They are a detached eclipsing binary with a spectral type of B8V and a brightness that dips by 0.05 magnitude once per orbit.^[13] This pair consists of two components of similar mass and type.^[4]

Further away from the primary system are stars of magnitude 7.3 and 10, designated Eta Muscae B and C. It is unclear if these stars are gravitationally–bound to the main pair. Evidence for an additional component has been found with a 30-year cycle in the orbital behavior of the main pair.^[9] The data suggests an orbital eccentricity of 0.29 for this suspected component, Eta Muscae D.^[14]