FEBRUARY 25 - 29, 2008
MONDAY, FEBRUARY 25
12 noon: Solar, Stellar, and Planetary Sciences Division Seminar. "Exospheric Sampling of Mercury's Surface Composition," Dr. Stefano A. Livi, Southwest Research Institute. Pratt Conference Room.
Abstract: ESA's BepiColombo mission to the planet Mercury includes a comprehensive set of advanced instruments. Strofio, one of the instruments on the SERENA neutral and ionizing particle suite on the Mercury Planet Orbit (MPO), is a high mass resolution, time-of-flight system for low energy neutral particles. Key questions addressed by Strofio are:
Strofio takes advantage of the direct coupling between the neutral atoms in the exosphere and their source regions in the outer layers of the regolith to answer fundamental questions about Mercury, its highly variable exosphere and its small but dynamic magnetosphere. The design of the Strofio sensor is driven by the attempt to achieve both isotopic resolving capability (goal is a cross talk of 10^-5 or better between two adjacent masses at the 50% level) and temporal resolution (a full-range spectrum can be collected in as short as 100 ms) within very limited resources (goal is 2 kg, 4W, 1,000 cm^3). Laboratory tests on an available prototype show that these goals are within reasonable reach. This instrument is currently being developed as an integral part of the Serena/BepiColombo project, but could be readily adapted to a number of future missions, including missions to study planetary atmospheres and exospheres, cometary missions, and fast flybys.
2:00 pm: Special Talk. "Lensed Star-Forming Galaxies and Obscured AGN," Dr. Jane Rigby, The Observatories of the Carnegie Institution of Washington. Phillips Auditorium.
Abstract: Most star formation occurred in rapid, violent starbursts that formed 20--2000 solar masses of stars per year, a history traced by the Spitzer Space Telescope. By exploiting the power of gravitational lensing, which amplifies distant galaxies by factors of 3--50, I have probed in detail the spectra and physical conditions inside these distant star-forming galaxies, in particular charting how the aromatic (PAH) features have systematically evolved in strength from z=0 to z=2. As such, rapidly star--forming galaxies at z=2 differ significantly from present-day analogues, with important consequences for star formation rate calibration, and for our general picture of the history of star formation. I will also discuss my work to understand obscured, accreting super- massive black holes. First, Ill show that the infrared to X-ray ratios of Chandra--selected AGN do not correlate with X-ray column density, a result inconsistent with simple torus models. Second, Ill discuss what we can learn from z=0 Compton--thick AGN: how their thick obscuring clouds reprocess UV/X-rays into the infrared, the shape of their intrinsic ionizing continuua, and the extinction law of the Compton--thick absorbing clouds. Finally, I'll describe how X-ray-faint AGN candidates can be selected by their non-stellar, power- law spectral energy distributions, toward identification of the long-sought population of distant Compton-thick AGN.
3:30 pm: Joint CfA/MIT Seminar on Neutron Stars and Supernova Remnants. "Radio Emission from the Magnetar SGR 1806-20 Giant Flare," Dr. Yosi Gelfand, New York University. Phillips Auditorium.
Abstract: On 2004 December 27, the brightest flash of gamma-rays yet observed was detected from the extremely magnetic neutron star (magnetar) SGR 1806-20 -- only the third, and by far most luminous, Giant Flare detected from such objects. Analysis of radio observations shortly after this event discovered a new, extremely bright but variable radio source at the location of this neutron star. In this talk, I will present the results from a long-term monitoring campaign of this radio source, which I will argue indicates this emission is being driven by material blown off the surface of the neutron star during this giant flare.
TUESDAY, FEBRUARY 26
2:30 pm: Joint Tufts/CfA/MIT Cosmology Seminar Series. Speaker: Prof. Roger Blandford, Stanford University/KIPAC. Topic: To be announced. Phillips Auditorium.
WEDNESDAY, FEBRUARY 27
12:15 pm: Ph.D. Colloquium. "Treasure Hunting in Photometric Seas: A Search for Eclipsing Binary Stars," Jonathan Devor. Phillips Auditorium.
Abstract: Eclipsing binary star systems provide the most accurate method of measuring both the masses and radii of stars, and enable us to constrain models of stellar structure and dynamics. We have taken advantage of the recent availability of large-scale multi-epoch photometric datasets, and analyzed 185,445 light curves from ten TrES fields and 218,699 light curves from the OGLE II bulge fields. In order to manage such large quantities of data, we developed a pipeline with which we systematically identified eclipsing binaries, found their components' absolute properties, and located rare cases for further follow-up. Of particular importance are low-mass eclipsing binaries, which are rare, yet critical for resolving the ongoing mass-radius discrepancy between theoretical models and observations. To this end, we have discovered over a dozen new low-mass eclipsing binary candidates, and spectroscopically confirmed the masses of five of them. Such assembly line astronomical analyses, which include both fitting data to models and identifying abnormal cases, are expected to become increasingly necessary with the next generation of ultra-large photometric surveys, such as Pan-STARRS and LSST.
4:00 pm: Initiative in Innovative Computing (IIC) Seminar. "Spiked Neuronal Networks and Gene Regulatory Networks: A Common Stochastic Framework and Method of Solution," Erol Gelenbe, Professor in the Dennis Gabor Chair Imperial College, London. Preceded by refreshments at 3:45 pm. Room 330, 60 Oxford Street, Cambridge. Event parking is available at the 52 Oxford Street Garage [map]. Please inform the parking attendant you are attending the IIC seminar. (The IIC seminar series schedule is updated often with additional information and seminars.)
Abstract: The Random Neural Network Model has been introduced to model that apparently probabilistic and spiked behaviour of many natural neuronal assemblies. We will first summarise the model and its main mathematical and algorithmic properties. Specifically we will detail its product form solution, and present its O(n^3) learning algorithm. Then we will describe applications to modeling natural cortico-thalamic oscillations, and to texture based detailed recognition for anomaly detection in MRI images of the brain. We will concluding by describing how very similar models can also be used to represent the dynamics and equilibrium of gene regulatory networks. The talk will be based on papers that we have published in the journals Neural Computation, BioSystems, Proceedings IEEE, IEEE Trans. on Neural Networks, and the Physical Review E.
THURSDAY, FEBRUARY 28
11:00 am: Institute for Theory and Computation (ITC) Colloquium. Speaker: Dr. Todd Thompson, Ohio State University. Topic: To be announced. Pratt Conference Room.
4:00 pm: Colloquium. "Taking Sides on the Dark Energy Issue," Prof. Rocky Kolb, University of Chicago, KICP. Preceded by tea at 3:30 pm. Phillips Auditorium.
Abstract: In the standard cosmological model, LambdaCDM, roughly 70% of the present mass/energy density of the universe is in the form of dark energy, or a cosmoillogical constant. But there are a number of other explanations for the observations, including modification of gravity, quintessence, and altering the Friedmann equation. Some of the possibilities have no dark energy, and in some of the solutions the expansion of the universe is not even accelerating. Theorists look to astronomers for direction. "Nothing more can be done by the theorists. In this matter it is only you, the astronomers, who can perform a simply invaluable service to theoretical physics."
SAO HUMAN RESOURCES NOTES
SAO Trust Fund Employees:
Please join us on Wednesday, February 27, from 2:00 to approximately 3:30 in Phillips Auditorium for a TIAA-CREF educational seminar on "Planning Ahead for Retirement." This seminar is targeted to individuals who are 10 or more years away from retirement. The presentation focuses on the three major questions that concern most participants in regard to their retirement:
In addition, the presentation will include information about the TIAA-CREF investments with emphasis on the lifestyle investment funds that have been recently added to our plan.
The seminar will be conducted by Sam Gagliardi, Senior Consultant, Individual Client Services, from the Boston office of TIAA-CREF. Mr. Gagliardi is a Certified Financial Planner with over 25 years of experience in the retirement and investment services industry.
Please contact Linda McDonald with questions concerning the TIAA-CREF Retirement Plan at (617) 496-7605, or via email to lmcdonald@cfa
Job Vacancies
An online listing of all current SAO job openings is available. For more information, please call Human Resources, ext. 5-7371, or view your nearest bulletin board.