The Calendar is prepared by the Web Services Group. The deadline for entries is 5:00 pm on Thursday of the preceding week. Entries may be submitted through interoffice mail (MS 77), by FAX at 617-384-7233, or via email to weekly_cal@cfa.
12 noon: Solar, Stellar, and Planetary Sciences Division Seminar. "Interaction of the Solar ULF waves with the Magnetosphere," E. Kaghashvili, University of New Hampshire. Phillips Auditorium.
Abstract: We present preliminary results of global simulations of the magnetosphere-ionosphere system to investigate how the solar wind and the interplanetary magnetic field couple ULF wave energy into the magnetosphere, which waves are most geo-effective and how the orientation influences the energy path down to the ionosphere. While more detailed investigation is underway, results based on some characteristics runs allow us to draw some conclusions about the effects of the wave spectrum, SW/IMF orientation, linearity/nonlinearity of the process and other parameters that are important to understand these processes. We also discuss the capabilities of the OpenGGCM model and future plans how these processes can be studied in more detail.
12:30 pm: Institute for Theory and Computation (ITC) Seminar. "Axisymmetric Stationary Flows in Astrophysics," Prof. Vasily Beskin, Lebedev Institute. Pratt Conference Room.
Abstract: An activity of many astrophysical sources (pulsars, active galactic nuclei) are associated with the presence of a strong magnetic field surrounding the rapidly rotating object and a relativistic particle outflow. The problem of transformation of electro-magnetic energy into particle kinetic one appears while one trying to explain an effective particle acceleration in the magnetic field. We discuss the conditions when the particle acceleration can be effective. Another examples of the highly magnetized flows are discussed as well. It is shown that the results of present numerical simulation are in good agreement with the analytical predictions.
1:30 pm: Special Seminar. "Transiting Exoplanets with HATNet," Dr. Gaspar Bakos, CfA. Phillips Auditorium.
Abstract: The past decade revolutionized our view of planetary systems via their detection around stars other than our Sun. There is an increasing excitement thanks to the continuous flow of discoveries, such as hot Jupiters orbiting close to their host star, resonant orbits of multiple planets, or highly eccentric massive planets. Especially important is the small ensemble (14) of planets that transit their central star, since the transit (or occultation) reveals a wealth of information: the planet's density, atmosphere, temperature, or perturbing companions. These quantities, in turn, are crucial for constraining theories of planetary formation and structure. Many interesting discoveries that will further improve our knowledge are on their way. The HAT Network of small telescopes is a major contributor to the field. I will briefly summarize its main properties, as well as the discovery of a puffed up planet "HAT-P-1b". I will highlight recent exciting results, such as a super-massive transiting planet, and a handful of strong candidates that will significantly impact the present census of transiting planets. Finally, I will hint on our future plans of HAT-South, a network with round-the-clock coverage and sensitivity to long period transits.
11:00 am: Optical and Infrared Astronomy Division Special Seminar. "Exoplanets with Large and Small Projects," Dr. Michael Shao, Jet Propulsion Laboratory. Pratt Conference Room.
Abstract: The talk will cover two related but separate topics. SIM Planet Quest is a space astrometric interferometer that can make very precise relative position measurements ~1 uas in ~ 1000sec. In order to detect planets with a 1uas astrometric signature, multiple 1uas measurements must be made and those errors should average down as roughly sqrt(N). We've now tested in the lab the long term stability of the SIM design and demonstrated a systematic noise flow below 0.1uas. With this in mind it's possible to redesign the terrestrial planet observing program so that an Earth Clone (1 Earth mass, 1AU scaled to stellar luminosity) could be found around the nearest ~64 stars. The 2nd topic is a small project, a collaboration of BU, MIT, GSFC and JPL to launch a high contrast coronagraph on a sounding rocket hopefully in July/August 2007. The goal is to detect the light from the Jovian companion to E Eri. The instrument is a 50cm telescope with a nulling interferometer/coronagraph and post coronagraph wavefront sensor driving a 32*32 deformable mirror. A brief overview of the project will be presented concentrating on the status of the nulling coronagraph being built at JPL.
12:30 pm: High Energy Astrophysics Division Lunch Talk. "Scaling Relations of the NoSOCS Galaxy Clusters," Dr. Paulo Lopes, CfA. Pratt Conference Room.
Abstract: Galaxy cluster properties such as total mass, X-ray temperature (TX) and luminosity (LX), velocity dispersion (sigma) and optical luminosity (Lopt) can be used to define scaling relations which are very helpful for studying the intra-cluster medium (ICM) and cosmology. An important tool for the latter is the cluster mass function and its evolution with cosmic time. However, the ability to compute the mass function for a large data set depends on the connection between cluster mass and an easily observable quantity. Underestimation of the scatter of the mass-observable relation could lead to controversial determinations of cosmological parameters. Here we investigate the connection between richness and X-ray properties of galaxy clusters, paying special attention to the impact of substructure on these relations. We have used literature data from BAX to prepare a list of X-ray emitting galaxy clusters in the northern sky and compare those to optically selected systems from DPOSS. We evaluated the recovery rate of the X-ray clusters in the optical as a function of richness, redshift and X-ray luminosity. Substructure alone can not explain the scatter in the richness to LX relation, but the comparison between richness and temperature is very sensitive to the exclusion of clusters showing signs of substructure. Additionally, we used SDSS data for the low redshift systems (z le 0.1) to estimate their velocity dispersion, mass and virial radius. The connection of these parameters to richness (and Lopt), as well as the X-ray properties, is further investigated.
4:30 pm: Joint CfA/Harvard University Atomic Physics Colloquium. Quantum Optimal Control: A Tool for Scalable Quantum Information Processing," Dr. Tommaso Calarco, ITAMP/Harvard University. Room 356, Jefferson Laboratory, Harvard University.
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.
11:00 am: Institute for Theory and Computation (ITC) Seminar. "The Build-up of Galaxies in the First 2 Gyr of the Universe," Dr. Rychard Bouwens, University of California, Santa Cruz. Pratt Conference Room.
12:30 pm: Optical and Infrared Astronomy Division Lunch Talk. "Determining the Type, Redshift, and Age of a Supernova Spectrum," Dr. Stephane Blondin, CfA. Pratt Conference Room.
Abstract: I will present an algorithm to automatically classify supernova (SN) spectra, and determine their redshift and age. This SuperNova IDentification tool (SNID) is based on the correlation techniques of Tonry & Davis. SNID relies on a large database of supernova spectral templates--- the majority of which come from the FLWO 1.5m telescope through the CfA Supernova Program (PI: Bob Kirshner). SNID is currently used by members of the ESSENCE project to distinguish between Type Ia and Type Ib/c supernovae at high redshift, and to identify ``peculiar'' SN Ia. It is also used to determine supernova redshifts (with a typical accuracy < 0.01) without a spectrum of the host galaxy. Last, the rest-frame age of an input SN spectrum is determined with a typical accuracy < 3 days, which enables an investigation of time-dilation effects in supernova spectra.
4:00 pm: Colloquium. "The Dwarf Planets of the Outer Solar System," Prof. Michael E. Brown, California Institute of Technology. (Anyone wishing to meet with the speaker should contact the host, Dr. Daniel Green, ext. 5-7440.) Preceded by tea at 3:30 pm. Phillips Auditorium.
Abstract: The past few years have seen an explosion in the discoveries of Pluto- and near Pluto-sized bodies in the outer solar system, giving rise to a new classification of "dwarf planets." Like Pluto, each of these largest dwarf planets has a unique story to tell about the history and evolution of the solar system. I'll discuss the discoveries of these objects and the new views of giant collisions, stellar encounters, and planetary rearrangement that we are gaining from their study.
12 noon: Solar, Stellar, and Planetary Sciences Division Seminar. "Role of Collisionless Reconnection in Solar Flares and Magnetospheric Substorms: a Comparative Study," A. Bhattacharjee, University of New Hampshire. Pratt Conference Room.
Abstract: Magnetic reconnection is widely believed to play an important role in magnetospheric substorms and solar flares. However, observations impose powerful constraints on theories of reconnection. Since the plasmas in the corona and the magnetosphere are characterized by very high values of the Lundquist number, it is likely that the relevant regime of reconnection is collisionless, and described by a generalized Ohm's law. Observations of substorms and flares demonstrate that they are generically not quasi-steady but impulsive phenomena, characterized not only by rapid growth, but a sudden change in the time-derivative of the reconnection rate, which places an additional burden on theory. We will present strong theoretical evidence that such fast and impulsive signatures can be obtained within the framework of two-fluid or Hall MHD theory, subject to the caveat that there are unresolved questions on how the present theoretical results on fast reconnection scale to large systems. We will also discuss the role of secondary instabilities such as ballooning (in the context of substorms) and tearing (in the context of flares) of thin current sheets that are inevitably formed during the dynamics of reconnection, and may play an important role in accounting for important features of observations. Finally, we will also identify processes such as the diamagnetic drift of electron and ion fluids that can quench the reconnection process nonlinearly, inhibiting explosive reconnection dynamics.
Thursday, April 19, 6:00 pm - 7:30 pm: Women, Science and Society Seminar Series. "The Estrogen Elixir: Women and Science in the Making and Unmaking of Hormone Replacement Therapy," Dr. Elizabeth Watkins, Associate Professor in the School of Medicine, University of California, San Francisco. HMS Conference Center, HIM Room, 77 Avenue Louis Pasteur, Boston. A small reception with the guest speaker will follow. Sponsored by the Harvard Graduate Women in Science and Engineering; Graduate School of Arts and Sciences; and Office of the Senior Vice Provost for Faculty Development and Diversity.
Abstract: Dr. Watkins studies interplay between medicine and culture, including the popularization of information about health and medicine and the roles of gender in medicine. Her most recent book, The Estrogen Elixir: A History of Hormone Replacement Therapy in America, tells the story of the use and public perception of estrogen since the 19th century.
Leave Donations Requested
Two SAO Trust Fund employees have been approved to receive leave donations. Due to medical emergencies, Nathalie Martimbeau of the Optical and Infrared Division and Donna Coletti of the Library have been approved as leave donor recipients in the Leave Transfer Program. Any SAO Trust Fund employee who wishes to donate annual leave to Nathalie or Donna should complete a Leave Donor Form and send it to MS17.
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.
A list of scientists currently visiting the CfA is available here.