Goals of the survey
- To detect occultations (eclipses by stars or brown dwarfs, or
transits by planets) in the light curves of young low-mass stars and
brown dwarfs in open clusters and star forming regions, and thus
- To detect transiting extra solar planets at young ages, and by
measuring their periods, masses and radii, further our understanding
of the formation and evolution of planetary systems.
- To discover young low mass eclipsing binaries, for which we can
measure dynamical masses and radii of both components, thereby
constraining the mass-radius and mass-luminosity relationships for low
mass stars and briown dwarfs at early ages.
- To further our understanding of the angular momentum of young, low
mass stars by measuring photometric rotation periods for large numbers
of objects at a range of ages from the stellar birthline to the
zero-age main sequence.
- To characterize and understand other forms of intrinsic
variability (e.g. flaring, micro flaring, accretion-induced
variability, stellar cycles) present in our targets.
- To understand the early lives of planetary systems. When do
planets form around stars? How many of them survive this early phase?
What is the role of environment? How fast do they cool down and
- To increase the number of low mass stars and brown dwarfs with
dynamically measured masses, known radii and a well-constrained age
estimate. These provide the only anchoring points for theoretical
evolutionary models of these objects. Systematic searches for
eclipsing binaries also provide information on the binarity properties
of these objects, which are contain information on the star formation
- To construct a much more extensive database of stellar rotation
periods, much more complete than has been possible previously in terms
of period range, stellar mass and stellar age, with sufficient numbers
of objects to draw statistically significant conclusions, and to use
these to improve our understanding of the way the angular momentum of
young stars is redistributed and exchanged with their
- Eclipsing events are rare: they occur only if a star possesses a
companion, if the inclination of the orbit is such that the companion
crosses the line of sight to the star, and only once per orbital
period. They can also be very shallow - of order 1% for Jupiter-like
companions to Sun-like stars. To detect these events, we must
therefore measure precise light curves for large numbers of
- For the detections to have maximum impact, we need to know as much
as possible about the systems, and in particular, their age. We target
open clusters and star forming regions because they provide the
largest concentrations of young stars whose ages and chemical
composition are relatively well known, and it is also relatively easy
to obtain rough mass estimates for the objects from their apparent
- Large-format, mosaic CCD cameras on 2- and 4-metre class
telescopes provide us with huge fields of view (up to one square
degree). These telescope apertures give us the sensitivity we need
well into the brown dwarf regime in nearby young open clusters and
star forming regions in typically a minute of integration.
- High-cadence monitoring is required to accurately measure the
shape of an event and improve our chances of detection.
- Long-term monitoring is required to increase our chances of
catching multiple events in the same system and to increase our
sensitivity to longer period systems.
- Data processing. A typical night's observing with the INT
telescope returns 25 GigaBytes of data. At CFH this is more like 50
Gigabytes. We want to measure tens of clusters for weeks of time. This
is a TeraByte project.
- Accurate measurement of photometry to levels of a few
- Stellar variabilty, though fantastically interesting and a major
science goal, is a major hurddle when it comes to searching for
sub-percent variations caused by planetary transits.
- Light curves provide only an estimate of the period and the
relative radii of the eclipsing systems we detect. In order to
determine their component masses and make sure they really are young
objects in the clusters we observed, rather than field objects that
happened to fall in the field of view, multi-epoch medium and
high-resolution spectroscopy is needed, and this can be challenging
for the relatively faint objects we detect.
- For more on the motivation, the design of the survey, and its
detection potential (including eclipse detection and spectroscopic
follow-up), check out this
- For more on the data processing and the noise properties of our
light curves, check out this
- For more on the technique we use to measure rotation periods,
check out this paper.