Theta1 Orionis E

For other stars with this Bayer designation, see θ Orionis.

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.

A near-infrared (4.5 micron) light curve for Theta¹ Orionis E, adapted from Morales-Calderón et al. (2012)^[3]

θ¹ Orionis E

θ1 Orionis E and nearby stars in the Trapezium Cluster
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	PMS[3]
Spectral type	G2 IV[4]
Variable type	Eclipsing[3]
Astrometry
Radial velocity (Rv)	34.3[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
Period (P)	9.89520 ± 0.0007[4] days
Semi-major axis (a)	34.430 ± 0.193[3] R☉
Eccentricity (e)	< 0.001[4]
Inclination (i)	73.7 ± 0.9[3]°
Semi-amplitude (K1) (primary)	84.2 ± 1.2[4] km/s
Semi-amplitude (K2) (secondary)	84.6 ± 1.3[4] km/s
Details
A
Mass	2.807 ± 0.048[3] M☉
Radius	7.1[7] R☉
Luminosity	29[8] L☉
Temperature	6,000[3] K
Rotational velocity (v sin i)	37[8] km/s
B
Mass	2.797 ± 0.048[3] M☉
Radius	7.1[7] R☉
Luminosity	29[8] L☉
Temperature	6,000[3] K
Rotational velocity (v sin i)	37[8] km/s
Age	0.5[8] 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 and are estimated to be only about 500,000 years old.^[8] 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]