Colloquia Schedule Fall 2015

Colloquia are on Tuesdays (unless otherwise indicated) at 3:30 pm in RLM 15.216B


Sep. 1	No Colloquium scheduled.
Sep. 8	"Convection in Cool Stars, as Revealed through Stellar Brightness Variations" As a result of the high precision and cadence of surveys like MOST, CoRoT, and Kepler, we may now directly observe the very low-level light variations arising from stellar granulation in cool stars. Here, we discuss how this enables us to more accurately determine the physical properties of Sun-like stars, to understand the nature of surface convection and its connection to magnetic activity, and to better determine the properties of planets around cool stars. Indeed, such sensitive photometric "flicker" variations are now within reach for thousands of stars, and we estimate that upcoming missions like TESS will enable such measurements for ~100 000 stars. We present recent results that tie "flicker" to granulation and enable a simple measurement of stellar surface gravity with a precision of ~0.1 dex. We use this, together and solely with two other simple ways of characterizing the stellar photometric variations in a high quality light curve, to construct an evolutionary diagram for Sun-like stars from the Main Sequence on towards the red giant branch. We discuss further work that correlates "flicker" with stellar density, allowing the application of astrodensity profiling techniques used in exoplanet characterization to many more stars. We also present results suggesting that the granulation of F stars must be magnetically suppressed in order to fit observations. Finally, we show that we may quantitatively predict a star's radial velocity jitter from its brightness variations, permitting the use of discovery light curves to help prioritize follow-up observations of transiting exoplanets. close Fabienne Bastien Pennsylvania State University host: Adam Kraus or Bill Cochran
Sep. 15	"Compact Objects in Globular Clusters" abstract Thomas Maccarone Texas Tech host: Karl Gebhardt
Sep. 22	"Convection in Low-Mass Stellar Evolution, or 'What about magnetic fields?' " abstract Gregory Feiden University of Uppsala, Sweden host: Andrew Mann
Sep. 29	"Tracing the Cosmic Shutdown of Star Formation in Massive Galaxies" abstract Katherine Whitaker Hubble Fellow, UMass Amherst host: Steve Finkelstein
Oct. 6	"The Assembly of Disk Galaxies" abstract Susan Kassin Space Telescope Science Institute host: Rachael Livermore
Oct. 13	*"Are we Correctly Measuring Star Formation Rates?"* abstract Kristen McQuinn University of Texas at Austin host: Adam Kraus
Oct. 20	No Colloquium Scheduled, to avoid conflict with: Bashfest 2015: Frank N. Bash Symposium 2015, October 18-20, 2015 Speaker: Dr. Frank N. Bash and invited speakers "New Horizons in Astronomy"
Oct. 27	Tinsley Scholar: Interstellar Group (visiting: Oct 25-31) "The Impact of Stellar Feedback on Molecular Clouds" abstract Stella Offner Affiliation: University of Massachusetts, Amherst host: Neal Evans
Nov. 3	Tinsley Scholar: Theory Group (visiting: late Oct - early Nov) "Disk Dynamos: Understanding the Origin of Galacic Magnetic Fields" abstract Ethan Vishniac Johns Hopkins University host: TBD
Nov. 10	"From TripleSpec to NEWS: Exoplanet Discovery Science with Bread and Butter Infrared Spectroscopy" abstract Philip S. Muirhead Boston University host: Adam Kraus
Nov. 17	"New Insights on Galaxy Formation from Comparisons of Simulated and Observed Galaxies" abstract Joel R. Primack UC Santa Cruz host: Paul Shapiro
Nov. 24	No colloquium scheduled.
Dec. 1	DeVaucouleurs Medalist "Expansion of the Universe Seen by Hubble" abstract Adam Riess Johns-Hopkins University, and Space Telescope Science Institute, and DeVaucouleurs Medalist host: Shardha Jogee, Chair
Dec. 8	"Supernovae and their Progenitor Systems (or lack thereof)" abstract Ori Fox Space Telescope Science Institute host: Jeff Silverman