The Architecture of the GW Ori Young Triple Star System and Its Disk: Dynamical Masses, Mutual Inclinations, and Recurrent Eclipses
Authors:
Czekala et al
Abstract:
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±0.09M⊙, and the circum-triple disk inclination, 137.6±2.0∘. Optical spectra spanning a 35 year 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 241.50±0.05 day period; a tertiary companion orbits that inner pair with a 4218±50 day period. 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≈2.7M⊙, MB≈1.7M⊙, MC≈0.9M⊙) and find strong evidence that at least one (and likely both) stellar orbital planes are misaligned with the disk plane by as much as 45∘. A V-band light curve spanning 30 years 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 tertiary approaches apoastron. 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.
CO Gas orbiting around the GG Tauri A triple System: rings beyond the ring ?
Authors:
Tang et al
Abstract:
We aim at unveiling the observational imprint of physical mechanisms that govern planetary formation in the young, multiple system GG Tau A. We present ALMA observations of 12CO and 13CO 3-2 and continuum at 0.9 mm at 0.35" resolution. The 12CO gas, found in the cavity of the dust ring where no 13CO gas is detected, confirms the existence of a CO accretion shock near the circumstellar disk of GG Tau Aa. The outer disk and the hot spot lying at the outer edge of the dust ring are observed both in 12CO and 13CO. The gas emission in the outer disk can be radially decomposed in a series of slightly overlapping gaussian rings, suggesting the presence of unresolved gaps. The dip closest to the disk center lies at a radius very close to the CO hot spot location (∼250−260~au). Studies of the CO excitation conditions reveal that the outer disk remains in the shadow of the ring. The hot spot probably results from local heating processes. The two latter points strongly support the hypothesis making the hot spot an embedded proto-planet shepherding the outer disk and accreting surrounding material which may be traced by the the redshifted component observed in the spectra around the hot spot.
