DECEMBER 17 - 21, 2007
MONDAY, DECEMBER 17
12 noon: Solar, Stellar, and Planetary Sciences Division Lunch Talk. "Direct Imaging of Debris Disks and Exoplanetary Systems," Stanimir Metchev, UCLA. Pratt Conference Room.
Abstract: This talk will summarize how direct imaging of optically thin circumstellar debris disks allows us to probe the physical properties of the circumstellar dust and the architectures of the planetary systems imbedded therein. I will also cover current results from efforts to study the extrasolar planets themselves using high-contrast imaging techniques, and the relevance of our present knowledge of low-mass brown dwarfs to the expected properties of extrasolar giant planets.
12:30 pm: High Energy Astrophysics Division Lunch Talk. "Long Term Superorbital Studies and Orbital Evolution in X-ray Binaries," Dr. Harsha Raichur, Raman Research Institute. Phillips Auditorium.
Abstract: The talk will be divided mainly into two parts, first part will discuss the long term superorbital studies (mainly Cen X-3 aperiodic intensity variations) and the second part will discuss the orbital evolution and apsidal motion of a few X-ray binary pulsars. Cen X-3 shows aperiodic long term intensity variations with timescales of a few days to a hundred days. This is in contrast to the superorbital intensity variations observed in other X-ray binary pulsar systems that are periodic (Her X-1, LMC X-4) or quasi-periodic (SMC X-1) and understood to occur due to obscuration of the central X-ray source by a warped or inclined precessing accretion disk. The Cen X-3 QPOs, orbital modulation and the pulsed fraction measurements in different source intensity states provide clues to understanding the aperiodic intensity variations. The results of these studies will be discussed in the talk. The orbital evolution of few high mass X-ray binaries will be presented. Tidal interaction, mass loss from the binary system and mass transfer from the normal companion star to the neutron star all contribute to orbital evolution. Orbits of some X-ray binaries which are eccentric also allow for measuring the rate of apsidal motion of the binary orbit. Measuring the rate of apsidal motion allows one to estimate the apsidal motion constant of the companion star which in turn can be a test for stellar structure models. The results of these studies will be presented.
TUESDAY, DECEMBER 18
12:30 pm: Institute for Theory and Computation (ITC) Seminar. "Multiple Galaxy Mergers, and Cosmological Context, and Elliptical Galaxy Formation," Greg Novak, University of California, Santa Cruz. Pratt Conference Room.
Abstract:I have performed a set of hydrodynamic simulations of multiple galaxy mergers both with and without a cosmological context using Gadget. Using a set of existing simulations of binary mergers of gas-rich spiral galaxies, I found that the simulated remnants reproduce the "fast-rotators" seen by the SAURON survey in many respects. However, the origin of slowly rotating, nearly spherical galaxies seen by the SAURON survey remains mysterious. In order to discover the physical processes and merger histories that are the keys to producing slow rotators, we consider both simple, idealized initial conditions (e.g. multiple major mergers or successive minor mergers of a given mass ratio) and more complex cases where the initial conditions taken from hydrodynamic cosmological simulations. The realistic set of initial conditions take into account the cosmological context in which galaxy formation takes place, including ongoing gas infall, while the idealized initial conditions provide essential intuition for interpreting the more realistic initial conditions.
WEDNESDAY, DECEMBER 19
12:30 pm: High Energy Astrophysics Division Lunch Talk. "The Prospects for a 15-Year Chandra Mission," Dr. Sabina Bucher, CfA. Pratt Conference Room.
Abstract: The viability of the Chandra spacecraft for a fifteen year mission will be determined by: (1) vehicle health, (2) the evolution of the Chandra orbit, and (3) science return. The spacecraft hardware is in a favorable position to support a fifteen year mission, but there are thermal concerns that cannot be ignored. We will walk through a top level summary of the state of the spacecraft hardware and an overview of the thermal concerns and the outlook for each. As the Chandra orbit continues to evolve it will bring the spacecraft to lower altitudes and closer to the magnetic poles than it has been to date. These changes will bring challenges and potential benefits. We will discuss the changes to the orbit and the impacts of thereof. As the hardware ages, the thermal conditions change and the orbit evolves mission scheduling must adapt, generally through introduction of new constraints. Many observations are now split due to constraints and in 2005 science time efficiency began to suffer. We will look at the state of current constraints and how they are expected to change. We will also discuss how constraints impact observation duration, science time efficiency and target availability. Finally we will use thermal trends and to preview allowed observation times into the future.
THURSDAY, DECEMBER 20
11:00 am: Science Education Seminar and Open Discussion. Weekly sessions focus on current department programs, literature reviews, and recent trends in science education and assessment. Some sessions feature outside speakers or guests. All members of the CfA community are welcome. Please contact Bruce Ward at bward@cfa, if you wish to attend any session. Phillips Auditorium.
SAO HUMAN RESOURCES NOTES
Leave Donations Requested
Due to a medical emergency, Joyce Janjigian of the Solar, Stellar and Planetary Science Division has been approved as a leave donor recipient in the Leave Transfer Program. Any SAO Trust Fund employee who wishes to donate annual leave to Joyce should complete a Leave Donor Form and send it to MS 17.
Under the Leave Transfer Program, Trust Fund employees may only donate annual leave to other Trust Fund employees and Federal employees may donate annual leave only to other Federal employees. If you should have any questions or are not able to access the form, please contact Anne LeBlanc, ext. 5-7371.
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.