Eta Muscae
Variable star in the constellation Musca
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Eta Muscae is a multiple[8][9] 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.[2] The system is located around 406 light years away from the Sun.[5] It is a member of the Lower Centaurs Crux subgroup of the Sco OB2 stellar association of co-moving stars.[10]
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Musca |
| Right ascension | 13h 15m 14.94123s[1] |
| Declination | −67° 53′ 40.5276″[1] |
| Apparent magnitude (V) | 4.79[2] |
| Characteristics | |
| Spectral type | B8V + sim. + K9.4XR? + A0p[3] or B7III + B7III[4] |
| B−V color index | −0.078±0.003[2] |
| Variable type | eclipsing binary |
| Astrometry | |
| Radial velocity (Rv) | −8.1±7.4[2] km/s |
| Proper motion (μ) | RA: +30.207[1] mas/yr Dec.: +17.921[1] mas/yr |
| Parallax (π) | 7.1001±0.1924 mas[1] |
| Distance | 405.7[5] ly (124.4[5] pc) |
| Absolute magnitude (MV) | −0.81[5] |
| Orbit[6] | |
| 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[6] | |
| Eta Mus Aa | |
| Mass | 3.30±0.04 M☉ |
| Radius | 2.14±0.02 R☉ |
| Luminosity | 223.77[2] (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[7] | |
| 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.[6][10] 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.[3]
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.[8] The data suggests an orbital eccentricity of 0.29 for this suspected component, Eta Muscae D.[14]