Theta1 Orionis E
θ1 Orionis E (Latinised as Theta1 Orionis E) is a double-lined spectroscopic binary located 4' north of θ1 Orionis A in the Trapezium Cluster. The two components are almost identical pre-main-sequence stars in a close circular orbit, and they show shallow eclipses that produce brightness variations of a few tenths of a magnitude.
θ1 Orionis E and nearby stars in the Trapezium Cluster | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Orion |
| Right ascension | 05h 35m 15.773s |
| Declination | −05° 23′ 10.02″ |
| Apparent magnitude (V) | 11.40 - 11.81 |
| Characteristics | |
| Evolutionary stage | PMS |
| Spectral type | G2 IV |
| Variable type | Eclipsing |
| Astrometry | |
| Radial velocity (Rv) | 34.3 km/s |
| Proper motion (μ) | RA: 1.45±0.03 mas/yr Dec.: 1.02±0.08 mas/yr |
| Parallax (π) | 2.557 ± 0.051 mas |
| Distance | 1,280 ± 30 ly (391 ± 8 pc) |
| Absolute magnitude (MV) | +1.43 |
| Orbit | |
| Period (P) | 9.89520 ± 0.0007 days |
| Semi-major axis (a) | 34.430 ± 0.193 R☉ |
| Eccentricity (e) | < 0.001 |
| Inclination (i) | 73.7 ± 0.9° |
| Semi-amplitude (K1) (primary) | 84.2 ± 1.2 km/s |
| Semi-amplitude (K2) (secondary) | 84.6 ± 1.3 km/s |
| Details | |
| A | |
| Mass | 2.807 ± 0.048 M☉ |
| Radius | 7.1 R☉ |
| Luminosity | 29 L☉ |
| Temperature | 6,000 K |
| Rotational velocity (v sin i) | 37 km/s |
| B | |
| Mass | 2.797 ± 0.048 M☉ |
| Radius | 7.1 R☉ |
| Luminosity | 29 L☉ |
| Temperature | 6,000 K |
| Rotational velocity (v sin i) | 37 km/s |
| Age | 500 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Each component of the binary system is slightly under 3 M☉. Although they have a subgiant spectral classification, they are still contracting onto the main sequence and are estimated to be only about 500 million years old. It is estimated that they will reach the main sequence as smaller hotter late-B stars.
The variability was first reported in 1954 and confirmed as an eclipsing binary in 2012. It has not been assigned a variable star designation but is listed in the New Catalogue of Suspected Variable Stars.