Astronomy Colloquia

Bayesian planet searches for the 10 cm/s radial velocity era

Speaker: 
Phil Gregory (UBC Physics & Astronomy)
Event Date and Time: 
Mon, 2015-10-05 15:30 - 16:30
Location: 
Hennings 318
Local Contact: 
Jaymie Matthews
Intended Audience: 
Graduate

Intrinsic stellar variability has become the main limiting factor for planet searches in both transit and radial velocity (RV) data. New spectrographs are under development like ESPRESSO and EXPRES that aim to improve RV precision by a factor of approximately 100 over the current best spectrographs, HARPS and HARPS-N. This will greatly exacerbate the challenge of distinguishing planetary signals from stellar-activity-induced RV signals. At the same time good progress has been made in simulating stellar activity signals.

Seesaw transits and anti-transits with Kepler

Speaker: 
Eric Agol
Event Date and Time: 
Tue, 2015-04-28 13:00 - 14:00
Location: 
Hennings 318

TBD

Eccentricities of planets in multi-planet extra-solar systems: Insights from classical secular theory.

Speaker: 
Christa Van Laerhoven
Event Date and Time: 
Mon, 2015-03-02 15:30 - 16:30
Location: 
Hennings 318
In planetary systems with more than one planet, gravitational
interactions cause orbital eccentricity variations. For non-resonant
systems, classical secular theory reveals that the eccentricities are
vector sums of contributions from several eigenmodes. The structure of
these secular eigenmodes can be calculated from the star and planet
masses and the planets' semi-major axes. Thus, the secular eigenmodes
can offer valuable insight into the long-term eccentricity behavior of
planets, even without knowing the current eccentricities.

An Overview of Canadian Astronomy

Speaker: 
Greg Fahlman
Event Date and Time: 
Mon, 2015-04-13 15:30 - 16:30
Location: 
Hennings 318

The Government of Canada recently announced an unprecedented award of $243.5M to enable Canada’s participation in the construction and operation of the Thirty Meter Telescope (TMT). This international project has its origins in a community-based Long Range Plan presented in 2000. A subsequent Plan in 2010 further amplified that case for this project among a suite of “World Observatories” that were planned for the early decades of the 21’st century.

The Young and the Restless Stars

Speaker: 
Lynne Hillenbrand
Event Date and Time: 
Mon, 2015-03-30 15:30 - 16:30
Location: 
Hennings 318

Young stars associated with regions of recent and ongoing star formation are amenable to study across almost the entire electromagnetic spectrum.  Furthermore, they are enigmatically variable over much of this range -- due to processes occurring in the inner circumstellar disk, the disk-to-star accretion zone, and perhaps the outflow regions.  The talk will give an overview of the relevant phenomena and present several types of state-of-the-art multiwavelength time domain data sets along with their physical interpretation.

A calibration of the stellar-mass fundamental plane at <z> = 0.5 using the micro-lensing induced flux ratio anomalies of macro-lensed quasars

Speaker: 
Paul Schechter (MIT)
Event Date and Time: 
Mon, 2015-03-23 15:30 - 16:30
Location: 
Hennings 318
We measure the stellar mass surface densities of early type galaxies
by observing the micro-lensing of macro-lensed quasars caused by
individual stars, including stellar remnants, brown dwarfs and red
dwarfs too faint to produce photometric or spectroscopic signatures.
Instead of observing multiple micro-lensing events in a single system,
we combine single epoch X-ray snapshots of ten quadruple systems, and
compare the measured relative magnifications for the images with those
computed from macro-models.

Circumstellar disks and planet formation with ALMA

Speaker: 
Meredith Hughes (Wesleyan)
Event Date and Time: 
Mon, 2015-03-16 15:30 - 16:30
Location: 
Hennings 318

Circumstellar disks provide the raw material and initial conditions for planet formation.  Millimeter-wavelength interferometry is a powerful tool for studying gas and dust in planet-forming regions, and it is undergoing an immense leap in sophistication with the advent of the ALMA interferometer.  I will discuss some ways in which we are using millimeter-wavelength interferometry to study the process of planet formation in circumstellar disks, with particular emphasis on the kinematics of turbulence in protoplanet

Alternative Lifestyles in Old Open Star Clusters: At the Interface of Stellar Evolution and Stellar Dynamics

Speaker: 
Robert Mathieu (U Wisc-Madison)
Event Date and Time: 
Mon, 2015-02-23 15:30 - 16:30
Location: 
Hennings 318

Nearly one quarter of all stars in old open star clusters do not follow classical single-star evolution paths. These non-standard evolutionary paths are closely associated with the large binary-star populations in these clusters.

Meteoritic and Planetary Constraints on Our Protoplanetary Disk

Speaker: 
Steve Desch (ASU)
Event Date and Time: 
Mon, 2015-02-02 15:30 - 16:30
Location: 
Hennings 318

Planets form from protoplanetary disks, and our own solar nebula was one example. To understand how planets form, we must first constrain the surface density of gas and dust in such disks, and how the surface density evolves over time.

The Origin of Stellar Masses

Speaker: 
Mark Krumholz (UCSC)
Event Date and Time: 
Mon, 2015-01-26 15:30 - 16:30
Location: 
Hennings 318

The mass distribution of newborn stars, known as the initial mass function (IMF), has a distinct peak at a mass slightly less than that of the Sun. This characteristic stellar mass appears to be nearly invariant across a huge range of star-forming environments, and over most of cosmic time. Explaining its origin and universality is one of the oldest problems in theoretical astrophysics, and a fully successful theory eludes us even today. In this talk, however, I describe recent progress toward an explanation for the mass scale of stars.

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