GW Orionis
GW Orionis is a T Tauri type pre-main sequence hierarchical triple star system.[5][7] It is associated with the Lambda Orionis star-forming region and has an extended circumtrinary protoplanetary disk.
 GW Orionis in the constellation Orion (yellow circle) | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Orion |
| Right ascension | 05h 29m 08.3929s[1] |
| Declination | +11° 52′ 12.666″[1] |
| Apparent magnitude (V) | 9.7–10.4[2] |
| Characteristics | |
| Spectral type | G8V[3] or G3V[4]/K0V[4] |
| Astrometry | |
| Radial velocity (Rv) | 28.33±0.18[5] km/s |
| Proper motion (μ) | RA: −2.351±0.061[1] mas/yr Dec.: −0.396±0.043[1] mas/yr |
| Parallax (π) | 2.4510 ± 0.0623[1] mas |
| Distance | 1,330 ± 30 ly (410 ± 10 pc) |
| Orbit[5] | |
| Primary | GW Orionis A |
| Companion | GW Orionis B |
| Period (P) | 241.50±0.05 d |
| Semi-major axis (a) | 1.25±0.05 AU |
| Eccentricity (e) | 0.13±0.01 |
| Inclination (i) | 157±1° |
| Longitude of the node (Ω) | 263±13° |
| Periastron epoch (T) | 2456681±4 HJD |
| Argument of periastron (ω) (secondary) | 197±7° |
| Semi-amplitude (K1) (primary) | 8.34±0.15 km/s |
| Orbit[5] | |
| Primary | GW Orionis AB |
| Companion | GW Orionis C |
| Period (P) | 4246±66 d |
| Semi-major axis (a) | 9.19±0.32 AU |
| Eccentricity (e) | 0.13±0.07 |
| Inclination (i) | 150±7° |
| Longitude of the node (Ω) | 282±9° |
| Periastron epoch (T) | 2453911±260 HJD |
| Argument of periastron (ω) (secondary) | 310±21° |
| Semi-amplitude (K1) (primary) | 2.38±0.23 km/s |
| Details | |
| GW Orionis A | |
| Mass | 2.80+0.36 −0.31[5] M☉ |
| Temperature | 5780±100[4] K |
| Rotational velocity (v sin i) | 43[4] km/s |
| Age | 0.3–1.3[5] Myr |
| GW Orionis B | |
| Mass | 1.68+0.21 −0.18[5] M☉ |
| Temperature | 5250±100[4] K |
| Rotational velocity (v sin i) | 50[4] km/s |
| Age | 0.3–1.3[5] Myr |
| GW Orionis C | |
| Mass | 1.15+0.40 −0.23[5] M☉ |
| Age | 0.3–1.3[5] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Observational history
GW Orionis first came to the attention of astronomers when it was published, as MHA 265-2, in a list of stars whose spectra have bright H and K lines of calcium.[8]
The multiple nature of GW Orionis was first discovered by Robert D. Mathieu, Fred Adams and David W. Latham during a radial velocity survey of late type H-alpha emission stars in the Lambda Orionis Association. Radial velocities of the primary star were measured from 45 high resolution spectra and were used to determine the orbital elements. A trend in the radial velocity residuals indicated either an additional stellar companion with an orbital period of years or a global asymmetric gravitational instability in a circumstellar disc.[7]
GW Orionis B and the third member of the system, GW Orionis C, were directly detected in 2011 using the IOTA interferometer located on Mount Hopkins in Arizona.[9]
Protoplanetary disk
GW Orionis has a large and massive protoplanetary disk surrounding it. The dust continuum emission suggests a disk radius of approximately 400 astronomical units.[10] The disk has an inclination of 137.6°.[5] Observations of the disk made with the Atacama Large Millimeter Array identified three separate dust rings located at ~46, 188, and 338 astronomical units from the center of the system. The three rings have estimated dust masses 74, 168, and 245 times that of the Earth. According to Jiaqing Bi and coauthors the outermost ring is the largest protoplanetary dust ring they are aware of. The dust rings are misaligned and the innermost dust ring is eccentric probably due to ongoing dynamical interactions between the triple stars and the circumtriple disk.[11]
Orbital architecture
The A and B components of GW Orionis form a double-lined spectroscopic binary with a 241-day period while component C orbits the inner pair with an 11.5 year period. It is likely that at least one of the stellar orbital planes is misaligned with the plane of the protoplanetary disk by as much as 45°.[5]
Variability
A light curve covering 30 years revealed 30 day eclipse events varying in depth between 0.1 and 0.7 magnitudes as well as a 0.2 magnitude sinusoidal oscillation that is aligned with the AB–C orbital period. This suggests that the A–B pair may be partially obscured due to dust in the disk as the pair approaches apoastron in the hierarchical orbit.[5]
References
- Brown, A. G. A.; et al. (Gaia collaboration). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics (in press). arXiv:2012.01533. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
- Shevchenko, V. S.; et al. (1998). "The quasi-Algol GW Ori: The nature of eclipses and estimation of the component masses". Astronomy Letters. 24 (4): 528–534. Bibcode:1998AstL...24..528S.
- Fang, M.; et al. (2014). "GW Orionis: Inner disk readjustments in a triple system". Astronomy and Astrophysics. 570. A118. arXiv:1407.4959. Bibcode:2014A&A...570A.118F. doi:10.1051/0004-6361/201424146. S2CID 119210837.
- Prato, L.; et al. (2018). "Orbital Solution for the Spectroscopic Binary in the GW Ori Hierarchical Triple". The Astrophysical Journal. 852 (1). 38. arXiv:1711.09449. Bibcode:2018ApJ...852...38P. doi:10.3847/1538-4357/aa98df. S2CID 119238386.
- Czekala, Ian; et al. (2017). "The Architecture of the GW Ori Young Triple-star System and Its Disk: Dynamical Masses, Mutual Inclinations, and Recurrent Eclipses". The Astrophysical Journal. 851 (2). 132. arXiv:1710.03153. Bibcode:2017ApJ...851..132C. doi:10.3847/1538-4357/aa9be7. S2CID 73629935.
- "GW Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-03-21.
- Mathieu, Robert D.; et al. (1991). "The T Tauri spectroscopic binary GW Orionis". The Astronomical Journal. 101: 2184–2198. Bibcode:1991AJ....101.2184M. doi:10.1086/115841.
- Joy, Alfred H.; Wilson, Ralph E. (1949). "Stars whose Spectra have Bright H and K Lines of Calcium". The Astrophysical Journal. 109: 231–243. Bibcode:1949ApJ...109..231J. doi:10.1086/145126.
- Berger, J.-P.; et al. (2011). "First astronomical unit scale image of the GW Orionis triple system". Astronomy and Astrophysics Letters. 529. L1. arXiv:1103.3888. Bibcode:2011A&A...529L...1B. doi:10.1051/0004-6361/201016219. S2CID 14305837.
- Fang, M.; et al. (2017). "Millimeter observations of the disk around GW Orionis". Astronomy and Astrophysics. 603. A132. arXiv:1705.01917. Bibcode:2017A&A...603A.132F. doi:10.1051/0004-6361/201628792. S2CID 119328687.
- Bi, Jiaqing; et al. (2020). "GW Ori: Interactions between a Triple-star System and Its Circumtriple Disk in Action". The Astrophysical Journal. 895 (1). L18. arXiv:2004.03135. Bibcode:2020ApJ...895L..18B. doi:10.3847/2041-8213/ab8eb4.