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.


Fabienne Bastien

Pennsylvania State University

host: Adam Kraus or Bill Cochran

Sep. 15

"Compact Objects in Globular Clusters"


Thomas Maccarone

Texas Tech

host: Karl Gebhardt

Sep. 22

"Convection in Low-Mass Stellar Evolution, or 'What about magnetic fields?' "


Gregory Feiden

University of Uppsala, Sweden

host: Andrew Mann

Sep. 29

"Tracing the Cosmic Shutdown of Star Formation in Massive Galaxies"


Katherine Whitaker

Hubble Fellow, UMass Amherst

host: Steve Finkelstein

Oct. 6

"The Assembly of Disk Galaxies"


Susan Kassin

Space Telescope Science Institute

host: Rachael Livermore

Oct. 13

"Are we Correctly Measuring Star Formation Rates?"


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"


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"


Ethan Vishniac

Johns Hopkins University

host: TBD

Nov. 10

"From TripleSpec to NEWS: Exoplanet Discovery Science with Bread and Butter Infrared Spectroscopy"


Philip S. Muirhead

Boston University

host: Adam Kraus

Nov. 17

"New Insights on Galaxy Formation from Comparisons of Simulated and Observed Galaxies"


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"


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)"


Ori Fox

Space Telescope Science Institute

host: Jeff Silverman

Visitors to the Department of Astronomy can find detailed information and maps on our Visiting Austin Page.

Please report omissions/corrections to: G. Orris at

23 November 2015
Astronomy Program · The University of Texas at Austin
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