Gaspard Duchene, Research Astronomer

Closed (1) Imaging and modeling of planet-forming disks

Closed. This professor is continuing with Spring 2017 apprentices on this project; no new apprentices needed for Fall 2017.

The formation of planets around stars is a central topic of modern astronomy. This happens in protoplanetary disks rich in gas and dust during the early stages of the star's evolution. After the planetary system is formed, residual dusty (debris) disks that are massive counterparts to our own Asteroid and Kuiper belts are also often observed. Obtaining high-resolution images of both types of disks and modeling them using radiative transfer tools allows to determine their global structure, evolution and whether already-formed planets are acting upon the disks.

This project builds on upcoming observations of protoplanetary disks with the Hubble Space Telescope and of debris disks with the Gemini Planet Imager. The goal of the project is to produce final publication-grade data products as well as to design disk models that reproduce the features observed in these images. A wide range of question can be addressed with these observations, from the geometry and exact nature of the dust grains (size, composition) contained in each disk to the implications for the planet formation.

The selected undergraduate student(s) will learn to process raw astronomical data into science-grade data products, to generate synthetic model images using a radiative transfer software (already existing), and to perform quantitative model fitting for this multi-parameter problem. The project involves collaboration with other scholars on campus and elsewhere.

Qualifications: Computer skills, including knowledge of UNIX/Linux are required. Knowledge and/or experience with programming is important. Good practice of any of the IDL and/or Python programming languages is desirable. Past introductory astronomy coursework is preferred but not absolutely necessary.

Weekly Hours: 6-9 hrs

Related website: http://astro.berkeley.edu/~gduchene

Closed (2) Extreme stellar multiplicity: understanding the limits of star formation

Applications for Fall 2017 are now closed for this project.

Most stars in our galaxy form in open clusters, which typically contains hundreds of stars. Furthermore, the star formation process results in a large fraction of binary and multiple stellar systems (i.e., containing 2 or more stars, unlike our Sun). The physical parameters (separation, mass ratio, eccentricity, ...) inform us on the detailed processes that led to their formation, as well as their subsequent evolution as they interacted with other stars in their immediate vicinity. Observations of solar-type stars have revealed the existence of a so-called brown dwarf desert, namely that these stars either host planets or fully-formed stars, but almost never the in-between "failed stars".

This project aims at understanding the reason for this deficit by searching for "scaled up" binary systems among stars whose mass is 3-5 times that of the Sun. The project is based on high-contrast adaptive optics imaging taken at multiple observatories, including UC's Lick Observatory, in which we are trying to identify very low-mass stellar companions. The goal of the project is to determine whether such companions are equally rare as, or much more frequent than, brown dwarfs around solar-type stars.

The selected student will undertake several activities throughout the semester:
- reading several articles to get familiar with the topic of stellar multiplicity;
- become familiar with the data at hand;
- participate in new observations at Lick Observatory;
- experiment with advanced methods of image analysis to uncover the faint companions we are looking for;
- perform a statistical analysis to determine whether candidate companions are physically bound to their primary;
- determine the frequency of very low-mass stellar companions.

Qualifications: Computer skills, including knowledge of UNIX/Linux and some programming experience (ideally IDL and/or Python, but other languages are fine) are required, while past introductory astronomy coursework is preferred but not absolutely necessary.

Weekly Hours: 9-12 hrs

Related website: http://astro.berkeley.edu/~gduchene