Observations with the correlation radial velocity meter of ADS 9731 were carried out during 1996-1997. We established that the components A and D of the visual quadruple system ADS 9731 are spectroscopic binaries with periods of 3.87 and 14.3 days, respectively. Their orbits are computed. New photometry has demonstrated the absence of eclipses in the close pair Aab. The spectral types and luminosities of all six components matching the are found.
The evolutionary status and origin of the most eccentric known binary in a quadruple system, 41 Dra (e=0.9754, period 3.413yr), are discussed. New observations include the much improved combined speckle-interferometric orbit, resolved photometry of the components and their spectroscopic analysis. The age of the system is 2.5+/-0.2Gyr; all four components are likely coeval. The high eccentricity of the orbit together with known age and masses provide a constraint on the tidal circularization theory: it seems that the eccentric orbit survived because the convective zones of the F-type dwarfs were very thin. Now as the components of 41 Dra are leaving the Main Sequence, their increased interaction at each periastron passage may result in detectable changes in period and eccentricity.
We investigate whether varying the dust composition (described by the optical constants) can solve a persistent problem in debris disk modeling --the inability to fit the thermal emission without overpredicting the scattered light. We model five images of the {beta} Pictoris disk: two in scattered light from the Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph at 0.58{mu}m and HST/Wide Field Camera 3 (WFC3) at 1.16{mu}m, and three in thermal emission from Spitzer/Multiband Imaging Photometer for Spitzer (MIPS) at 24{mu}m, Herschel/PACS at 70{mu}m, and Atacama Large Millimeter/submillimeter Array at 870{mu}m. The WFC3 and MIPS data are published here for the first time. We focus our modeling on the outer part of this disk, consisting of a parent body ring and a halo of small grains. First, we confirm that a model using astronomical silicates cannot simultaneously fit the thermal and scattered light data. Next, we use a simple generic function for the optical constants to show that varying the dust composition can improve the fit substantially. Finally, we model the dust as a mixture of the most plausible debris constituents: astronomical silicates, water ice, organic refractory material, and vacuum. We achieve a good fit to all data sets with grains composed predominantly of silicates and organics, while ice and vacuum are, at most, present in small amounts. This composition is similar to one derived from previous work on the HR 4796A disk. Our model also fits the thermal spectral energy distribution, scattered light colors, and high-resolution mid-IR data from T-ReCS for this disk. Additionally, we show that sub-blowout grains are a necessary component of the halo.
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