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Register a new userThe Architecture of the V892 Tau System: the Binary and its Circumbinary Disk
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We present high resolution millimeter continuum and CO line observations for the circumbinary disk around V892 Tau to constrain the stellar and disk properties. The total mass of the two near-equal-mass A stars is estimated to be $6.0pm0.2,M_{odot}$ based on our models of the Keplerian-dominated gas disk rotation. The detection of strong ionized gas emission associated with the two stars at 8 mm, when combined with previous astrometric measurements in the near-infrared, provides an updated view of the binary orbit with $a=7.1pm0.1$ au, $e=0.27pm0.1$, and $P=7.7pm0.2$ yr, which is about half of a previously reported orbital period. The binary orbital plane is proposed to be near coplanar to the circumbinary disk plane (with a mutual inclination of only $Delta=8pm4.2$ deg; another solution with $Delta=113$ deg is less likely given the short re-alignment timescale). An asymmetric dust disk ring peaking at a radius of 0.2 is detected at 1.3 mm and its fainter counterparts are also detected at the longer 8 and 9.8 mm. The CO gas disk, though dominated by Keplerian rotation, presents a mild inner and outer disk misalignment, such that the inner disk to the SW and outer disk to the NE appear brighter than their counterparts at the opposite disk sides. The radial extension of the disk, its asymmetric dust ring, and the presence of a disk warp could all be explained by the interaction between the eccentric binary and the circumbinary disk, which we assume were formed with non-zero mutual inclination. Some tentatively detected gas spirals in the outer disk are likely produced by interactions with the low mass tertiary component located 4 to the northeast. Our analyses demonstrate the promising usage of V892 Tau as an excellent benchmark system to study the details of binary--disk interactions.
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We report the discovery of a circumbinary disk around the Herbig Ae/Be system v892 Tau. Our detailed mid-infrared images were made using segment-tilting interferometry on the Keck-1 Telescope and reveal an asymmetric disk inclined at ~60 degs with an inner hole diameter of 250 mas (35 AU), approximately 5X larger than the apparent separation of the binary components. In addition, we report a new measurement along the binary orbit using near-infrared Keck aperture masking, allowing a crude estimate of orbital parameters and the system mass for the first time. The size of the inner hole appears to be consistent with the minimum size prediction from tidal truncation theory, bearing a resemblance to the recently unmasked binary CoKu Tau/4. Our results have motivated a re-analysis of the system spectral energy distribution, concluding the luminosity of this system has been severely underestimated. With further study and monitoring, v892 Tau should prove a powerful testing ground for both predictions of dynamical models for disk-star interactions in young systems with gas-rich disks and for calibrations of pre-main-sequence tracks for intermediate-mass stars.
KH 15D is a system which consists of a young, eccentric binary, and a circumbinary disk which obscures the binary as the disk precesses. We develop a self-consistent model that provides a reasonable fit to the photometric variability that was observed in the KH 15D system over the past 60 years. Our model suggests that the circumbinary disk has an inner edge $r_{rm in}lesssim 1 {rm au}$, an outer edge $r_{rm out} sim {rm a few au}$, and that the disk is misaligned relative to the stellar binary by $sim$5-16 degrees, with the inner edge more inclined than the outer edge. The difference between the inclinations (warp) and longitude of ascending nodes (twist) at the inner and outer edges of the disk are of order $sim$10 degrees and $sim$15 degrees, respectively. We also provide constraints on other properties of the disk, such as the precession period and surface density profile. Our work demonstrates the power of photometric data in constraining the physical properties of planet-forming circumbinary disks.
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 ${}^{13}$CO and C${}^{18}$O $J$=2-1 transitions permits a measurement of the total stellar mass in this system, $5.29 pm 0.09,M_odot$, and the circum-triple disk inclination, $137.6 pm 2.0^circ$. 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 $241.50pm0.05$ day period; a tertiary companion orbits that inner pair with a $4218pm50$ 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 ($M_mathrm{A} approx 2.7,M_odot$, $M_mathrm{B} approx 1.7,M_odot$, $M_mathrm{C} approx 0.9,M_odot$) and find strong evidence that at least one (and likely both) stellar orbital planes are misaligned with the disk plane by as much as $45^circ$. A $V$-band light curve spanning 30 years reveals several new $sim$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 $sim$1 Myr old.
We performed mapping observations of the Class I protostellar binary system L1551 NE in the C$^{18}$O ($J$=3-2), $^{13}$CO ($J$=3-2), CS ($J$=7-6), and SO ($J_N$=7$_8$-6$_7$) lines with Atacama Submillimeter Telescope Experiment (ASTE). The ASTE C$^{18}$O data are combined with our previous SMA C$^{18}$O data, which show a $r sim$300-AU scale Keplerian disk around the protostellar binary system. The C$^{18}$O maps show a $sim$20000-AU scale protostellar envelope surrounding the central Keplerian circumbinary disk. The envelope exhibits a northeast (blue) - southwest (red) velocity gradient along the minor axis, which can be interpreted as a dispersing gas motion with an outward velocity of 0.3 km s$^{-1}$, while no rotational motion in the envelope is seen. In addition to the envelope, two $lesssim$4000 AU scale, high-velocity ($gtrsim$1.3 km s$^{-1}$) redshifted $^{13}$CO and CS emission components are found to $sim$40$^{primeprime}$ southwest and $sim$20$^{primeprime}$ west of the protostellar binary. These redshifted components are most likely outflow components driven from the neighboring protostellar source L1551 IRS 5, and are colliding with the envelope in L1551 NE. The net momentum, kinetic and internal energies of the L1551 IRS 5 outflow components are comparable to those of the L1551 NE envelope, and the interactions between the outflows and the envelope are likely to cause the dissipation of the envelope and thus suppression of the further growth of the mass and mass ratio of the central protostellar binary in L1551 NE.
We present sensitive ALMA observations of TWA 3, a nearby, young ($sim$10 Myr) hierarchical system composed of three pre-main sequence M3--M4.5 stars. For the first time, we detected ${}^{12}$CO and ${}^{13}$CO $J$=2-1 emission from the circumbinary protoplanetary disk around TWA 3A. We jointly fit the protoplanetary disk velocity field, stellar astrometric positions, and stellar radial velocities to infer the architecture of the system. The Aa and Ab stars ($0.29pm0.01,M_odot$ and $0.24pm0.01,M_odot$, respectively) comprising the tight ($P=35$ days) eccentric ($e=0.63pm0.01$) spectroscopic binary are coplanar with their circumbinary disk (misalignment $< 6^{circ}$ with 68% confidence), similar to other short-period binary systems. From models of the spectral energy distribution, we found the inner radius of the circumbinary disk ($r_mathrm{inner} = 0.50 - 0.75$ au) to be consistent with theoretical predictions of dynamical truncation $r_mathrm{cav}/a_mathrm{inner} approx 3$. The outer orbit of the tertiary star B ($0.40pm0.28,M_odot$, $asim65 pm 18$ au, $e=0.3pm0.2$) is not as well constrained as the inner orbit, however, orbits coplanar with the A system are still preferred (misalignment $ < 20^{circ}$). To better understand the influence of the B orbit on the TWA 3A circumbinary disk, we performed SPH simulations of the system and found that the outer edge of the gas disk ($r_mathrm{outer}=8.5pm0.2$ au) is most consistent with truncation from a coplanar, circular or moderately eccentric orbit, supporting the preference from the joint orbital fit.
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