Weekly Calendar of Events

MARCH 2 - 6, 2015


10:30 am: Atomic and Molecular Physics Division Seminar. "Collisions in Molecular Spectroscopy," Piotr Wcislo, Institute of Physics, Nicolaus Copernicus University. Pratt Conference Room.

Abstract: Ultra-accurate spectroscopic measurements together with appropriate ab initio calculation allows not only to study properties of interaction between molecules in the presence of light, but also to follow interesting dynamics of the molecular gas. Such development is crucial for both optical metrology and fundamental molecular physics studies. Our recent results on an intriguing problem that have remained unsolved for 25 years will be presented. A collisional inhomogeneous broadening of the H2 Q(1) line perturbed by Ar was observed for the first time almost three decades ago. Several attempts were made to explain the line broadening from ab initio calculations, which however resulted in fundamental discrepancies between theory and experiment. Our new approach to this issue properly reconstructs the experimental spectra and shows that the reason of so far discrepancies is completely different from the one suspected in the precedent literature. I will also briefly discuss the physical meaning of the parameters of the Hartmann-Tran profile, which has been recently recommended as a good candidate for H2O spectra analysis and is likely to be adopted as a standard for atmospheric spectra studies.

Noon: Solar, Stellar, and Planetary Sciences Division Seminar. "The Space Photometry Revolution of Asteroseismology and Exoplanets," Dr. Daniel Huber, Sydney Institute for Astronomy. Pratt Conference Room.

Abstract: Asteroseismology - the study of stellar oscillations - is a powerful tool to probe the structure and evolution of stars. In addition to the wealth of newly discovered exoplanets, space-based telescopes such as Kepler have revolutionized asteroseismology by detecting oscillations in thousands of stars from the main sequence to the red-giant branch. In this talk I will highlight the most recent asteroseismic discoveries by Kepler/K2 with a particular focus on exoplanet host stars, and discuss efforts to improve stellar properties of the Kepler parent sample to derive accurate planet occurrence rates. I will also discuss the prospects for asteroseismic studies with TESS, including its role for the synergy of asteroseismology and galactic astronomy to probe the chemo-dynamical evolution of stellar populations in our galaxy (galactic archeology).


1:00 pm: Institute for Theory and Computation (ITC) Pizza Lunch. "Magnetic Reconnection in Heliospheric, Laboratory, and Astrophysical Plasmas," Nick Murphy, CfA, and "Magnetic Reconnection in Relativistic Astrophysical Jets," Lorenzo Sironi, CfA. Phillips Auditorium.


12:30 pm: High Energy Astrophysics Division Lunch Talk. 1) "Pan-STARRS and Quasars: Examining Quasar Variability with the Largest Optical Dataset," Eric Morganson, CfA; 2) "Resolving Hard X-rays from Supernova Remnants with NuSTAR," Laura Lopez, CfA; 3) "Spitzer Observations of the Variability of Sgr A*," Joseph Hora, CfA. Phillips Auditorium.

Abstract: 1) Pan-STARRS1 is a 2 petabyte optical dataset that covers three quarters of the sky 12 times each. Its depth and coverage make it a unique survey to study the variability of large sample. Combining PS1 with SDSS, we have measured the variability of 100,000 quasars on time scales from days to decades. We are continuing to pursue quasar variability with in the Time Domain Spectroscopic Survey, an SDSS subproject that has begun taking 250,000 spectra of variables, including 150,000 quasar spectra. 2) Launched in 2012, NuSTAR is the first satellite to focus at hard X-ray energies of 3-79 keV. Since then, NuSTAR has observed several young supernova remnants (SNRs), with the primary scientific objectives of mapping and characterizing non-thermal emission as well as detecting radioactive decay lines of Ti-44. In this talk, I will discuss new results from targeted NuSTAR observations of SNRs, including SN 1987A, G1.9+0.3, Cassiopeia A, Tycho, and Kepler. In particular, NuSTAR has detected Ti-44 in SN 1987A and Cassiopeia A and found hints of asymmetric originating explosions. By contrast, NuSTAR has not detected Ti-44 from any Type Ia SNRs, and the limits on Ti yields constrain the progenitor scenarios. NuSTAR observations have also enabled the localization of the hardest (> 10 keV) non-thermal X-rays, which are associated with synchrotron emission from electrons accelerated by the SNR shocks. I will show spatially resolved spectroscopic analyses of these data and will consider the implications regarding the particle acceleration process. 3) The Galactic center black hole is by far the closest test bed to study the conditions for and the mechanisms of accretion onto a supermassive black hole. Sgr A* is the fluctuating source of electromagnetic radiation derived from the accretion flow or jet. Its variable radiation has been detected at radio, submillimeter, near-infrared (NIR) and X-ray wavelengths. Observations and modeling of this source have produced detailed descriptions of the spectral energy distribution of Sgr A*, the radiation mechanisms for its steady emission, and the statistical behavior of its variability. Despite these efforts, a surprising number of basic questions are not answered: Is the variable emission related to an accretion disk or a jet, and from where in the jet or the disk does the emission originate? Does the variability t different wavelengths originate at the same location, and if so, what are the emission processes connecting the variability in different wavelength regimes? Does the variability carry signatures of general relativistic effects, and can we infer basic black hole parameters, e.g., spin? How does Sgr A* compare with other massive black holes or AGN? I will describe our efforts to obtain data with Spitzer, Chandra, and ground-based observatories to address these questions.

4:30 pm: Joint ITAMP/HQOC Quantum Sciences Seminar. "Merging Metamaterials with Quantum Photonics," Vladimir Shalaev, Purdue University. Tea served at 4:00 after short student talk. Jefferson 250, Department of Physics, Harvard University.


11:00 am: Institute for Theory and Computation (ITC) Colloquium. "Magnetars Life Cycle: Birth, Evolution and Death," Dr. Nanda Rea, CSIC-IEEC. Pratt Conference Room.

Abstract: Magnetars are the strongest magnets we know of, and show themselves via powerful X/gamma-ray steady and flaring emission. The energetics of such flares in our Galaxy second only the supernova explosions. In this talk I will first review the observational characteristics of these highly magnetic pulsars, and some recent discoveries in the field. Subsequently, I will present what we currently know about their life-cycle, through detailed simulations of neutron star magneto-thermal evolution and pulsar population synthesis. I will then finish with some considerations on how the study of the Galactic population of magnetars might constrain their possible connection with Gamma Ray Bursts.

4:00 pm: Colloquium. "Magnetism Matters," Dr. Sarah Gibson, National Center for Atmospheric Research/High Altitude Observatory. Preceded by tea at 3:30 pm. Phillips Auditorium.

Abstract: Magnetism defines the complex and dynamic solar corona. Twists and tangles in coronal magnetic fields build up energy and ultimately erupt, hurling plasma into interplanetary space. These coronal mass ejections (CMEs) are transient riders on the ever-outflowing solar wind, which itself possesses a three-dimensional morphology shaped by the global coronal magnetic field. Coronal magnetism is thus at the heart of any understanding of space weather at the Earth. I will describe the current state of the art in coronal magnetometry, and present results from the Coronal Multichannel Polarimeter (CoMP) at Mauna Loa Solar Observatory (MLSO), which since 2011 has taken polarimetric observations of the solar corona in the near-infrared on a near-daily basis. I will discuss work in progress that utilizes forward modeling to synthesize polarimetric data at multiple heights and vantage points, and at wavelengths from radio to infrared to visible to ultraviolet. The goal is to use such synthetic testbeds to determine the ideal set of observations for constraining the coronal magnetic field, and to establish a Data-Optimized Coronal Field Model (DOC-FM) that efficiently incorporates these data into global magnetic models. This work will provide essential tools and motivation for the planning and implementation of future coronal polarimetric projects and missions spanning a broad range of wavelengths.


The CfA will be hosting the 26th International Symposium on Space Terahertz Technology, March 16-18, 2015, at the Knafel Center in the Radcliffe Yard on the Harvard University campus. Additional information can be found here.

The Calendar is prepared by the Web Services Group. Entries may be submitted via email to weekly_cal@cfa.


Section Photo