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.

For other stars with this Bayer designation, see θ Orionis.
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[6] mas
Distance1,280 ± 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
Mass2.807 ± 0.048[3] M☉
Radius7.1[7] R☉
Luminosity29[8] L☉
Temperature6,000[3] K
Rotational velocity (v sin i)37[8] km/s
B
Mass2.797 ± 0.048[3] M☉
Radius7.1[7] R☉
Luminosity29[8] L☉
Temperature6,000[3] K
Rotational velocity (v sin i)37[8] km/s
Age500[8] Myr
Other designations
41 Ori E, BD−05°1315E, COUP 732, 2MASS J05351577-0523100
Database references
SIMBADdata

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.[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]

References
  1. Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D.; Light, R. M.; Marsh, K. A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W. A.; Wheelock, S.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally Published in: 2003yCat.2246....0C. 2246. Bibcode:2003yCat.2246....0C.
  2. Kukarkin, B. V.; Kholopov, P. N.; Artiukhina, N. M.; Fedorovich, V. P.; Frolov, M. S.; Goranskij, V. P.; Gorynya, N. A.; Karitskaya, E. A.; Kireeva, N. N.; Kukarkina, N. P.; Kurochkin, N. E.; Medvedeva, G. I.; Perova, N. B.; Ponomareva, G. A.; Samus, N. N.; Shugarov, S. Y. (1981). "Catalogue of suspected variable stars. Moscow, Acad. Of Sciences USSR Shternberg,1951 (1981)". Nachrichtenblatt der Vereinigung der Sternfreunde E.V. (1981). Bibcode:1981NVS...C......0K.
  3. Morales-Calderón, M.; Stauffer, J. R.; Stassun, K. G.; Vrba, F. J.; Prato, L.; Hillenbrand, L. A.; Terebey, S.; Covey, K. R.; Rebull, L. M.; Terndrup, D. M.; Gutermuth, R.; Song, I.; Plavchan, P.; Carpenter, J. M.; Marchis, F.; García, E. V.; Margheim, S.; Luhman, K. L.; Angione, J.; Irwin, J. M. (2012). "YSOVAR: Six Pre-main-sequence Eclipsing Binaries in the Orion Nebula Cluster". The Astrophysical Journal. 753 (2): 149. arXiv:1206.6350. Bibcode:2012ApJ...753..149M. doi:10.1088/0004-637X/753/2/149. S2CID 44908832.
  4. Costero, R.; Allen, C.; Echevarría, J.; Georgiev, L.; Poveda, A.; Richer, M. G. (2008). "The Escaping Spectroscopic Binary θ^1 Ori E". IV Reunión Sobre Astronomía Dinámica en Latino América (Eds. C. Allen. 34: 102. Bibcode:2008RMxAC..34..102C.
  5. Olivares, J.; Sánchez, L. J.; Ruelas-Mayorga, A.; Allen, C.; Costero, R.; Poveda, A. (2013). "Kinematics of the Orion Trapezium Based on Diffracto-Astrometry and Historical Data". The Astronomical Journal. 146 (5): 106. arXiv:1310.0769. Bibcode:2013AJ....146..106O. doi:10.1088/0004-6256/146/5/106. S2CID 119110490.
  6. Kounkel, Marina; et al. (2017). "The Gould's Belt Distances Survey (GOBELINS) II. Distances and Structure toward the Orion Molecular Clouds". The Astrophysical Journal. 834 (2). 142. arXiv:1609.04041. Bibcode:2017ApJ...834..142K. doi:10.3847/1538-4357/834/2/142. S2CID 26439367.
  7. Herbig, G. H.; Griffin, R. F. (2006). "Θ1 Orionis E as a Spectroscopic Binary". The Astronomical Journal. 132 (5): 1763. Bibcode:2006AJ....132.1763H. doi:10.1086/507769.
  8. Huenemoerder, David P.; Schulz, Norbert S.; Testa, Paola; Kesich, Anthony; Canizares, Claude R. (2009). "X-Ray Emission and Corona of the Young Intermediate-Mass Binary θ1 Ori E". The Astrophysical Journal. 707 (2): 942–953. arXiv:0911.0189. Bibcode:2009ApJ...707..942H. doi:10.1088/0004-637X/707/2/942. S2CID 55747631.
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