Gaspard Duchêne

  Associate Research Astronomer and Lecturer

   Astronomy Department
   269 Campbell Hall    UC Berkeley
   Berkeley CA 94720-3411 USA
    gduchene (at) berkeley.edu          Fax: (510) 642 3411
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   Research

   Publications / CV (pdf)

   Teaching

   UC Adaptive Optics Seminar
Stellar multiplicity and star formation
Stellar multiplicity is ubiquitous among stars in our Galaxy. To characterize the end result of star formation, I perform large-scale surveys of stellar populations to determine their statistical properties (frequency, distributions of semi-major axes and mass ratios, ...). In particular, I have studied stars of all masses among:
  • Embedded protostars;
  • Pre-main sequence stars;
  • Members of young open clusters.
Check out the ARAA review on Stellar Multiplicity I wrote with Adam Kraus in 2013. Most recently, I have initiated a search for the lowest mass stellar companions to stars whose mass is 3 to 5 times that of the Sun, which requires high-contrast imaging techniques.
       
    
In-depth studies of selected multiple systems
Some young multiple systems are highly valuable as benchmarks or particularly unique systems. I conduct dedicated follow-up studies to
  • map their orbits to determine the masses of individual pre-main sequence stars to test the validity of evolutionary models (see the example of V773 Tau on the right - Boden et al. 2012);
  • study the presence and properties of circumstellar disks in multiple systems, with an eye on the general topic of planet formation within multiple systems.
Imaging of protoplanetary and debris disks
Circumstellar disks around pre-main sequence stars represent the birthplace for planetary systems while the debris disk phenomenon occurs after planet formation, when collisions between large planetesimals produce short-lived small dust grains. My work in this area focuses on obtaining high-resolution imaging datasets that help resolve the spatial structure and determine the dust properties of disks. To this end, I use a combination of:
  • the Hubble Space Telescope;
  • adaptive optics on the largest ground-based telescopes;
  • (sub)millimeter interferometer arrays.

Images to the right show the HR 4796 A debris ring in total and polarized intensity at 2 micron, from data obtained with the state-of-the-art adaptive optics-fed Gemini Planet Imager (Perrin et al. 2015). On the bottom is a 3 color composite Hubble Space Telescope of an edge-on protoplanetary disk with its associated collimated jet.

In 2018, I contributed to an ARAA review on Debris Disks with Meredith Hughes and Brenda Matthews, building on Herschel, ALMA, HST and ground-based adaptive optics imaging of these systems.

    

Radiative transfer modeling of disks
Full quantitative analyses of the high-quality imaging disk images require the use of a radiative transfer model. To this end, I have contributed to the development of the Monte Carlo-based MCFOST radiative transfer code (Pinte et al. 2006; 2009) to produce synthetic
  • (polarized) scattered light images;
  • thermal imaging maps;
  • spectral energy distributions.
I use MCFOST to probe dust grain growth and vertical settling within protoplanetary disks as well as the detailed geometrical structure and dust porosity in debris disks. 

Last updated: 11 September 2017