Theta1 Orionis E
Star in the constellation Orion
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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.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Orion |
| Right ascension | 05h 35m 15.773s[1] |
| Declination | −05° 23′ 10.02″[1] |
| Apparent magnitude (V) | 11.40 – 11.81[2] |
| Characteristics | |
| Evolutionary stage | Pre-main sequence[3] |
| Spectral type | G2 IV[4] |
| Variable type | Eclipsing[3] |
| Astrometry | |
| Radial velocity (Rv) | +29.7±0.2[5] km/s |
| Proper motion (μ) | RA: 1.45±0.03[6] mas/yr Dec.: 1.02±0.08[6] mas/yr |
| Parallax (π) | 2.557±0.051 mas[6] |
| Distance | 1,280 ± 30 ly (391 ± 8 pc) |
| Absolute magnitude (MV) | +1.43[7] |
| Orbit[5] | |
| Period (P) | 9.89522(3) days |
| Semi-major axis (a) | 34.22±0.18 R☉ (0.1589±0.0008 AU) |
| Eccentricity (e) | 0 |
| Inclination (i) | 73.7±0.9° |
| Periastron epoch (T) | 3281.0455(94) HJD |
| Semi-amplitude (K1) (primary) | 83.36±0.29 km/s |
| Semi-amplitude (K2) (secondary) | 84.57±0.29 km/s |
| Details[5] | |
| A | |
| Mass | 2.755±0.043 M☉ |
| Radius | 6.26±0.31 R☉ |
| Luminosity | 24.8±4.6 L☉ |
| Surface gravity (log g) | 3.29±0.04 cgs |
| Temperature | 5,150±200 K |
| Rotational velocity (v sin i) | 30.7±2.1 km/s |
| Age | ≤0.1 Myr |
| B | |
| Mass | 2.720±0.043 M☉ |
| Radius | 6.25±0.30 R☉ |
| Luminosity | 24.7±4.5 L☉ |
| Surface gravity (log g) | 3.28±0.04 cgs |
| Temperature | 5,150±200 K |
| Rotational velocity (v sin i) | 30.7±2.1 km/s |
| Age | ≤0.1 Myr |
| Other designations | |
| 41 Ori E, BD−05°1315E, COUP 732, 2MASS J05351577-0523100 | |
| 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[8] and are estimated to be less than 100,000 years old.[5] It is estimated that they will reach the main sequence as smaller hotter late-B stars.[7]
The variability was first reported in 1954[2] 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.[2]