TY - JOUR
T1 - The Architecture of the GW Ori Young Triple-star System and Its Disk
T2 - Dynamical Masses, Mutual Inclinations, and Recurrent Eclipses
AU - Czekala, Ian
AU - Andrews, Sean M.
AU - Torres, Guillermo
AU - Rodriguez, Joseph E.
AU - Jensen, Eric L.N.
AU - Stassun, Keivan G.
AU - Latham, David W.
AU - Wilner, David J.
AU - Gully-Santiago, Michael A.
AU - Grankin, Konstantin N.
AU - Lund, Michael B.
AU - Kuhn, Rudolf B.
AU - Stevens, Daniel J.
AU - Siverd, Robert J.
AU - James, David
AU - Gaudi, B. Scott
AU - Shappee, Benjamin J.
AU - Holoien, Thomas W.S.
N1 - Funding Information:
I.C. acknowledges support from the Smithsonian Institution and Stanford KIPAC for the production of this manuscript. I.C. and E.J. acknowledge useful conversations with Lisa Prato about GW Ori, and we greatly appreciate her sharing her results in advance of publication. I.C. acknowledges helpful conversations with Maxwell Moe and Jack Lissauer about GW Ori and related systems and would like to thank Eric Nielsen, Bruce Macintosh, and Rebekah Dawson for helpful discussions about astrometry and orbital dynamics. S.A. acknowledges the very helpful support provided by the NRAO Student Observing Support program related to the early development of this project. G.T. acknowledges partial support for this work from NSF grant AST-1509375. This paper makes use of the following ALMA data: 2012.1.00496.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/ NRAO, and NAOJ. This research made extensive use of the Julia programming language (Bezanson et al. 2017) and Astropy (Astropy Collaboration et al. 2013).
Funding Information:
IRAF is distributed by the National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.
Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.
PY - 2017/12/20
Y1 - 2017/12/20
N2 - We present spatially and spectrally resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of gas and dust orbiting the pre-main-sequence hierarchical triple-star system GW Ori. A forward modeling of the 13CO and C18O J = 2-1 transitions permits a measurement of the total stellar mass in this system, 5.29 ± 0.09 M⊙, and the circumtriple disk inclination, 137°.6 ± 2°.0. Optical spectra spanning a 35 yr period were used to derive new radial velocities and, coupled with a spectroscopic disentangling technique, revealed that the A and B components of GW Ori form a double-lined spectroscopic binary with a period of 241.50 ± 0.05 days; a tertiary companion orbits that inner pair with a period of 4218 ± 50 days. Combining the results from the ALMA data and the optical spectra with three epochs of astrometry in the literature, we constrain the individual stellar masses in the system (MA ≈ 2.7 M⊙, MB ≈1.7 M⊙, MC ≈0.9 M⊙) and find strong evidence that at least one of the stellar orbital planes (and likely both) is misaligned with the disk plane by as much as 45°. A V-band light curve spanning 30 yr reveals several new ∼30-day eclipse events 0.1-0.7 mag in depth and a 0.2 mag sinusoidal oscillation that is clearly phased with the AB-C orbital period. Taken together, these features suggest that the A-B pair may be partially obscured by material in the inner disk as the pair approaches apoastron in the hierarchical orbit. Lastly, we conclude that stellar evolutionary models are consistent with our measurements of the masses and basic photospheric properties if the GW Ori system is ∼1 Myr old.
AB - We present spatially and spectrally resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of gas and dust orbiting the pre-main-sequence hierarchical triple-star system GW Ori. A forward modeling of the 13CO and C18O J = 2-1 transitions permits a measurement of the total stellar mass in this system, 5.29 ± 0.09 M⊙, and the circumtriple disk inclination, 137°.6 ± 2°.0. Optical spectra spanning a 35 yr period were used to derive new radial velocities and, coupled with a spectroscopic disentangling technique, revealed that the A and B components of GW Ori form a double-lined spectroscopic binary with a period of 241.50 ± 0.05 days; a tertiary companion orbits that inner pair with a period of 4218 ± 50 days. Combining the results from the ALMA data and the optical spectra with three epochs of astrometry in the literature, we constrain the individual stellar masses in the system (MA ≈ 2.7 M⊙, MB ≈1.7 M⊙, MC ≈0.9 M⊙) and find strong evidence that at least one of the stellar orbital planes (and likely both) is misaligned with the disk plane by as much as 45°. A V-band light curve spanning 30 yr reveals several new ∼30-day eclipse events 0.1-0.7 mag in depth and a 0.2 mag sinusoidal oscillation that is clearly phased with the AB-C orbital period. Taken together, these features suggest that the A-B pair may be partially obscured by material in the inner disk as the pair approaches apoastron in the hierarchical orbit. Lastly, we conclude that stellar evolutionary models are consistent with our measurements of the masses and basic photospheric properties if the GW Ori system is ∼1 Myr old.
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U2 - 10.3847/1538-4357/aa9be7
DO - 10.3847/1538-4357/aa9be7
M3 - Article
AN - SCOPUS:85039734863
VL - 851
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
M1 - 132
ER -