Research Interests

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Circumstellar Disk Composition and Evolution

Explaining the remarkable variety of planets that encircle other stars requires that we study the early history of planets and how they interact with their natal environment, the circumstellar disk. Do most stars possess disks massive enough to form planets? How is material distributed radially and vertically in the disk? The density of material controls the timescales for planet formation, and the temperature and viscosity of the disk control the transport of solids. How does disk material dissipate? How do disks and planetesimals interact? How do planets obtain their compositions and volatiles? How do giant impacts shape planetary architectures and habitability?

Using the high spatial resolution and sensitivity of the Hubble Space Telescope and ground-based telescopes such as Magellan, I am studying dusty circumstellar disks as the birthplaces of planetary systems. The observations elucidate disk geometries and dust composition and in an ensemble fashion teach us about the evolution of disks and the timescales for planet formation within them. I try to connect the disks around other stars to our understanding of planet formation in our own Solar System and in other systems.

Disk Imaging

Visual and near-infrared imaging provides detailed morphologies and colors of resolved disks. I have been PI or co-I on many programs HST programs over the years to image disks, particulary nearby dusty debris disks. Debris dust arises from the collisions and evaporation of planetesimals, and it is these same planetesimals which are the building blocks for planets. The compositions and dynamics of planetesimals may reflect and affect the final composition and architectures of the planetary systems. (e.g. Schneider, Weinberger, Becklin, Debes & Smith (2009) )

Disk Spectroscopy

I am PI of a Cycle 19 HST project to make spatially resolved spectra of disks in visible scattered light. The color of cold dust grains provide the only possible study of their compositions. We will be able to estimate the organic-to-silicate ratio of the dust and constrain its place of formation and subsequent processing. Large ground based telescopes provide sensitivity combined with high angular resolution in the mid-infrared, from which we can learn about the temperature and density profiles of disks. By studying the grain composition directly with spectroscopy over a range of distances from the star, I try to learn about the processes of planet building and collisions that occur in disks. (e.g. Debes, Weinberger & Schneider (2008) and Roberge, Weinberger & Malumuth (2005))

Spectral Energy Distribution of BD+20
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Disk Evolution Studies

I have used ground-based telescopes and Spitzer Space Telescope to search for disks around special classes of nearby stars with ages from as young as 5 Myr to 1 Gyr. Ultimately, we need to understand disk removal mechanisms and timescales as well as the stochastic collisions that create disk dust. From the ground, I do follow-up with Carnegie's Magellan Telescopes to study the stellar properties (e.g. Weinberger et al. 2011)

Young Stars

I search for young stars in the Stellar neighborhood that might be good laboratories for studying disk evolution and I use Magellan to study the young stars and brown dwarfs in nearby star forming regions. Together, I try to correlate stellar and disk properties. I use the duPont telescope and CAPSCam to measure parallactic distances to nearby stars; distances and the stellar luminosities that follow from them are fundamental to understand disk and stellar evolution. (e.g. Weinberger et al. 2013)

Planets

With Alan Boss, we are undertaking an astrometric search for gas giant planets and brown dwarfs orbiting nearby low-mass dwarf stars with the 2.5 m duPont Telescope at the Las Campanas Observatory in Chile. We plan to follow about 100 nearby (primarily within about 10 pc) low-mass stars, principally late M, L, and T dwarfs, for 10 yr or more, in order to detect very low-mass companions with orbital periods long enough to permit the existence of habitable, Earth-like planets on shorter-period orbits. These stars are generally too faint and red to be included in ground-based Doppler planet surveys, which are often optimized for FGK dwarfs. The smaller masses of late M dwarfs also yield correspondingly larger astrometric signals for a given mass planet. Our search will help to determine whether gas giant planets form primarily by core accretion or by disk instability around late M dwarf stars. (Boss et al. 2009, Anglada-Escude' et al. 2013)

Active Galactic Nuclei

My PhD thesis consisted of near-infrared speckle observations of six nearby AGN made with the Hale 200-inch Telescope on Palomar Mountain and the 10-m W. M. Keck Telescope on Mauna Kea (e.g. Diffraction-Limited Imaging and Photometry of NGC 1068 , Weinberger, A. J., Neugebauer, G., and Matthews, K., 1999)