GW Orionis

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GW Orionis
GW Orionis-map.png
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]
Variable type T Tau
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  mas [1]
Distance 1,330 ± 30  ly
(410 ± 10  pc)
Orbit [5]
PrimaryGW Orionis A
CompanionGW 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)151+1
−2 [5] °
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]
PrimaryGW Orionis AB
CompanionGW Orionis C
Period (P)4246±66 d
Semi-major axis (a)9.19±0.32  AU
Eccentricity (e)0.13±0.07
Inclination (i)130+28
−27 [5] °
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 2.74+0.15
−0.52 [5] [6]   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 1.65+0.10
−0.31 [5] [6]   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 0.88+0.85
−0.19 [5] [6]   M☉
Age 0.3–1.3 [5]   Myr
Other designations
MHA 265-2, HD  244138, HIP  25689, TYC  708-1901-1, 2MASS J05290838+1152126 [7]
Database references
SIMBAD data

GW Orionis is a T Tauri type pre-main sequence hierarchical triple star system. [5] [8] It is associated with the Lambda Orionis star-forming region and has an extended circumtrinary protoplanetary disk.

Contents

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. [9]

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, published in 1991. 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. [8]

GW Orionis B and the third member of the system, GW Orionis C, were detected directly in 2011 using the IOTA interferometer located on Mount Hopkins in Arizona. [10]

Variability

Visual band light curves for several eclipse minima of GW Orionis, adapted from Czekala et al. (2017) GWOriLightCurve.png
Visual band light curves for several eclipse minima of GW Orionis, adapted from Czekala et al. (2017)

GW Orionis is a variable star with quasi-periodic brightness changes. The apparent magnitude varies between 9.7 and 10.4 with dimming events of between 0.1 and 0.7 magnitudes roughly every 30 days, as well as more sinusoidal variations with an amplitude of 0.2 magnitudes over 11.6 years.

An initial interpretation of the variability was that a disk of material around component B was eclipsing component A and causing the dimming events, but it is now thought that the eclipses are caused by partial obscuration of both stars by a much larger ring which precesses around the pair. [5]

Protoplanetary disk

The inner ring of GW Orionis: model and SPHERE observations Eso2014a.tif
The inner ring of GW Orionis: model and SPHERE observations

GW Orionis has a large and massive protoplanetary disk surrounding it. The dust continuum emission suggests a disk radius of approximately 400 astronomical units. [11] 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. [6]

GW Orionis 1.jpg
Schematic diagram showing a proposed geometry of the GW Orionis system. [6]
GW Orionis 2.jpg
ALMA self-calibrated dust continuum map of the GW Orionis system. [6]

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]

See also

Related Research Articles

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Mintaka, designation Delta Orionis and 34 Orionis, is a multiple star system some 1,200 light-years from the Sun in the constellation of Orion. Together with Alnitak and Alnilam, the three stars form Orion's Belt, known by many names among ancient cultures. The star is located very close to the celestial equator. When Orion is near the meridian, Mintaka is the rightmost of the Belt's stars when viewed from the Northern Hemisphere facing south.

Chi<sup>1</sup> Orionis Star in the constellation Orion

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Pi<sup>4</sup> Orionis Binary star system in the constellation Orion

Pi4 Orionis (π4 Ori, π4 Orionis) is a binary star system in the western part of the Orion constellation. It is visible to the naked eye with an apparent visual magnitude of 3.7. Based upon an annual parallax shift of 3.1 mass, it is located roughly 1,050 light-years from the Sun.

<span class="mw-page-title-main">Sigma Orionis</span> Five-star system in the constellation Orion

Sigma Orionis or Sigma Ori is a multiple star system in the constellation Orion, consisting of the brightest members of a young open cluster. It is found at the eastern end of the belt, south west of Alnitak and west of the Horsehead Nebula which it partially illuminates. The combined brightness of the component stars is magnitude 3.80.

HD 98800, also catalogued as TV Crateris, is a quadruple star system in the constellation of Crater. Parallax measurements made by the Hipparcos spacecraft put it at a distance of about 150 light-years away. The system is located within the TW Hydrae association (TWA), and has received the designation TWA 4.

<span class="mw-page-title-main">HD 37017</span> Binary star system in the constellation Orion

HD 37017 is a binary star system in the equatorial constellation of Orion. It has the variable star designation V1046 Orionis; HD 37017 is the identifier from the Henry Draper Catalogue. The system is a challenge to view with the naked eye, being close to the lower limit of visibility with a combined apparent visual magnitude of 6.55. It is located at a distance of approximately 1,230 light years based on parallax, and is drifting further away with a radial velocity of +32 km/s. The system is part of star cluster NGC 1981.

<span class="mw-page-title-main">HD 141569</span> Star in the constellation Libra

HD 141569 is an isolated Herbig Ae/Be star of spectral class A2Ve approximately 364 light-years away in the constellation of Libra. The primary star has two red dwarf companions at about nine arcseconds. In 1999, a protoplanetary disk was discovered around the star. A gap in the disk led to speculation about a possible extrasolar planet forming in the disk.

<span class="mw-page-title-main">AA Tauri</span> Star in the constellation Taurus

AA Tauri is a young variable star in the equatorial constellation of Taurus, located in the Taurus-Auriga star-forming region. It is too faint to view with the naked eye, having an apparent visual magnitude that varies from 12.2 down to 16.1. The star is located approximately 439 light-years away from the Sun based on parallax, and is drifting further away with a radial velocity of +17 km/s.

Pi<sup>1</sup> Orionis Star in the constellation Orion

Pi1 Orionis (π1 Ori, π1 Orionis) is a star in the equatorial constellation of Orion. It is faintly visible to the naked eye with an apparent visual magnitude of 4.74. Based upon an annual parallax shift of 28.04 mas, it is located about 116 light-years from the Sun.

Omicron2 Orionis is a solitary star in the constellation Orion. It has an apparent visual magnitude of 4.06, which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 17.54 mas, it is around 186 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an interstellar absorption factor of 0.09 due to intervening dust.

<span class="mw-page-title-main">32 Orionis</span> Triple star system in the constellation Orion

32 Orionis is a triple star system in the equatorial constellation of Orion. It has the Bayer designation A Orionis, while 32 Orionis is the Flamsteed designation. This system is visible to the naked eye as a faint point of light with a combined apparent visual magnitude of 4.20. It is located approximately 303 light-years away from the Sun based on parallax, and is drifting further away with a radial velocity of +18.6 km/s.

Theta<sup>2</sup> Orionis Star in the constellation Orion

Theta2 Orionis is a multiple star system in the constellation Orion. It is a few arc minutes from its more famous neighbour the Trapezium Cluster, also known as θ1 Orionis.

Phi<sup>1</sup> Orionis Binary star system in the constellation Orion

Phi1 Orionis is a binary star system in the constellation Orion, positioned less than a degree to the south of Meissa. It is visible to the naked eye with an apparent visual magnitude of 4.42. The distance to this system, based upon an annual parallax shift of 3.0 mas, is around 1,090 light-years.

Psi<sup>2</sup> Orionis Spectroscopic binary system in the constellation of Orion

Psi2 Orionis a binary star system in the equatorial constellation of Orion. It has an apparent visual magnitude of 4.6, indicating that it is visible to the naked eye. Based upon an annual parallax shift of 2.87 mass, it is roughly 1,100 light years distant from the Sun.

<span class="mw-page-title-main">GG Tauri</span> Star in the constellation Taurus

GG Tauri, often abbreviated as GG Tau, is a quintuple star system in the constellation Taurus. At a distance of about 450 light years away, it is located within the Taurus-Auriga Star Forming Region. The system comprises three stars orbiting each other in a hierarchical triple system, known as GG Tauri A, and another binary star system more distant from the central system, known as GG Tauri B.

<span class="mw-page-title-main">RW Aurigae</span> Young binary star system in the constellation Auriga

RW Aurigae is a young binary system in the constellation of Auriga about 530 light years away, belonging to the Taurus-Auriga association of the Taurus Molecular Cloud. RW Aurigae B was discovered in 1944.

<span class="mw-page-title-main">GI Tauri and GK Tauri</span> Binary star system in the constellation of Taurus

GK Tauri is a young T Tauri-type pre-main sequence star in the constellation of Taurus about 421 light years away, belonging to the Taurus Molecular Cloud.

HD 100453 is a binary star system which lies in the constellation Centaurus about 350 light years away from the Sun and is a member of the open cluster Scorpius–Centaurus association.

<span class="mw-page-title-main">CQ Tauri</span> Star in the constellation Taurus

CQ Tauri is a young variable star in the equatorial constellation of Taurus. It is too faint to be visible to the naked eye with an apparent visual magnitude that ranges from 8.7 to 12.25. The distance to this star is approximately 487 light years based on parallax measurements, and it is drifting further away with a radial velocity of ~23 km/s. It appears to be part of the T-association Tau 4. CQ Tauri lies close enough to the ecliptic to undergo lunar occultations.

References

  1. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics . 649: A1. arXiv: 2012.01533 . Bibcode:2021A&A...649A...1G. doi: 10.1051/0004-6361/202039657 . S2CID   227254300. (Erratum:  doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. ↑ 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 .
  3. ↑ 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.
  4. 1 2 3 4 5 6 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.
  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 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. When we combined the RV constraints with the disk-based constraint on Mtot, we found stellar masses of MA = 2.7 M⊙, MB = 1.7 M⊙, and MC = 0.9 M⊙, to a precision of ± 0.3 M⊙
  6. 1 2 3 4 5 6 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 . The stellar masses have been constrained to be ~2.7, 1.7, and 0.9 M⊙, respectively (Czekala et al. 2017)
  7. ↑ "GW Ori". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2018-03-21.
  8. 1 2 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 .
  9. ↑ 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 .
  10. ↑ 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.
  11. ↑ 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.
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