Weekly Calendar of Events

OCTOBER 20 - 24, 2014


Noon: Solar, Stellar, and Planetary Sciences Division Seminar. "Measuring the Asymmetries in Transit Light Curves," George Zhou, Mt. Stromlo Observatory. Pratt Conference Room.

Abstract: We are using asymmetries in the high precision transit light curves from Kepler to reveal the dynamics and shape of transiting planets. I will describe our measurement of the spin-orbit misalignment of KOI-368.01, a 110-day period stellar binary system orbiting a gravity darkened star. Such measurements for long-period systems are difficult from the ground for long-period systems using traditional techniques. The shape of planets can also be measured from their transit geometry. Planets that are rotationally oblate will induce an asymmetric transit differing from that of a spherical planet. I will describe our search for rotationally oblate warm-Jupiters in the Kepler dataset, and a tentative detection for the oblateness of Kepler-39b, a brown dwarf in a 21-day period orbit.


1:00 pm: Institute for Theory and Computation (ITC) Seminar. "The Dark Side of Galaxy Evolution," Andrew Hearin, Yale University; and, "Early Time Gamma-Ray Burst Afterglows, Thick Shells and Thin Shells," Hendrik van Eerten, Max-Planck-Institut fur Extraterrestrische Physik. Pratt Conference Room.


11:00 am: Optical and Infrared Astronomy Division Seminar. "Resolving the Assembly of Massive Galaxies at Cosmic Noon," Stijn Wuyts, Max-Planck-Institut fur Extraterrestrische Physik. Pratt Conference Room.

12:30 pm: High Energy Astrophysics Division Lunch Talk. "Tracing the High-Energy Emission of Gamma-Ray Radio-Loud Quasars: The Case of RGB1512+020A," Giulia Migliori, CfA. Phillips Auditorium.

Abstract: Radio loud quasars with a gamma-ray detected blazar component and an extended X-ray jet are unique objects to map the high energy jet emission. X-ray to gamma-ray observations and modelling of the broadband jet emission can be used to investigate the processes responsible for the high-energy radiation, infer the jet parameters and test whether in jets the power is efficiently transported from the vicinity of the supermassive black hole to kiloparsec scales. In addition, the optical spectra of the cores carry the information on the accretion flow and allow to relate the accretion and ejection phenomena in powerful quasars. In this talk, I will present our study of the radio source RGB 1512+020A. We report the first detection of a bright extended X-ray jet. The source is classified as a flat spectrum radio quasar, with detected optical broad lines and gamma-ray emission, however it displays an unusually weak UV continuum. I will present the results of the core analysis based on new optical, UV and X-ray observations.

3:00 pm: Radio and Geoastronomy Division Talk. "A New Probe of the Distribution of Dark Matter in Galaxies," Sukanya Chakrabarti, Rochester Institute of Technology. Room M-340, 160 Concord Avenue.

Abstract: The cold dark matter paradigm of structure formation is successful at recovering the basic skeletal structure of the universe -- the large-scale distribution of galaxies. However, agreement between theory and observation is less secure when this model is applied to galactic (and sub-galactic) scales. The "missing satellites problem" and discrepancies between the observed structure of dwarf galaxies and simulations have prompted us to develop an inverse method of characterizing the dark matter distribution. The extended atomic hydrogen disks of galaxies are ideal tracers of tidal interactions with satellites and the galactic gravitational potential well. Our "Tidal Analysis" method allows us to approximately infer the mass, and relative position (in radius and azimuth) of satellites from analysis of observed disturbances in outer gas disks, without requiring knowledge of their optical light. Generalizations of the method allow for an approximate inference of density parameters of the dark matter halo. I will present the proof of principle of this method by applying it to galaxies with known optical companions. I will also present our earlier prediction for a dim and yet undiscovered companion of the Milky Way. I will end by presenting recent work that incorporates the tidal effects of all the known Milky Way satellites, with their orbits constrained by their measured proper motions.

4:30 pm: Joint ITAMP/HQOC Quantum Sciences Seminar. "Hacking the Superconducting Nanowire: Electronics and Single-Photon Detectors," Karl Berggren, MIT. 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. Speaker: Peng Oh, University of California, Santa Barbara. Pratt Conference Room.

4:00 pm: Colloquium. "Supermassive Black Hole Caught Red Handed in Stellar Homicide," Dr. Suvi Gezari, University of Maryland . Preceded by tea at 3:30 pm. Phillips Auditorium.

Abstract: It was first proposed by theorists in the late 1970's that an inevitable consequence of a massive black hole lurking in the center of a galaxy is that stars will pass close enough to the black hole to be ripped apart by its extreme tidal forces and consumed. Rees (1988) suggested that the luminous flare of radiation from the accretion of the bound tidal debris could be used as a signpost for an otherwise dormant and undetectable central black hole. The first observational tidal disruption event candidates emerged in the late 1990's from an archival search of the ROSAT All-Sky Survey in the form of luminous soft X-ray outbursts from several otherwise inactive galaxies. Since then, about two dozen tidal disruption event candidates have been discovered across the electromagnetic spectrum. I will review these candidates, and highlight our most recent discoveries from coordinated monitoring with the GALEX Time Domain Survey in the UV and the Pan-STARRS1 Survey in the optical. For the first time we are collecting enough information from the crime scene (observations) to determine both the victim (chemical composition and structure of the star) and the identity of the perpetrator (black hole mass). I will conclude with the promising detection rates of the next generation of time domain surveys, and how large samples of these events can be used as transient probes of accretion physics, jet formation, and black hole demographics.


12:30 pm: Radio and Geoastronomy Division Lunch Talk. "Hierarchy, Sheets, and Filaments: A High Resolution View of Dense Gas in Nearby Molecular Clouds," Shaye Storm, University of Maryland. Pratt Conference Room (note change of venue).

Abstract: Stars rarely form in isolation, so it is critical to understand how the parsec-scale molecular cloud environment shapes the formation of individual dense cores at the sub-0.1 pc scale. To address the pathway to filament and core formation in clustered environments, we developed the CARMA Large Area Star Formation Survey, which spectrally imaged dense gas tracer lines across 800 square arcminutes of the Perseus and Serpens Molecular clouds with 7'' angular resolution. I will discuss the key results from initial papers. First, we found that filaments seen with Herschel show substructure in our high-resolution maps, and that several filaments show strong radial velocity gradients. I will compare the observed filament gradients with results from numerical simulations of filament formation from turbulent flows to support the idea that the observed filaments are self-gravitating and accreting material from an environment that is flattened at larger scales. Second, we found that the hierarchical complexity of dense gas structures, as measured by our new non-binary dendrogram code applied to our N2H+ J=1-0 data, correlates with the amount of star formation activity in different parts of the Perseus Molecular Cloud. Lastly, I will show how we can use dendrogram-identified structures in combination with high-resolution maps of centroid velocity and line-of-sight velocity dispersion to determine the line-of-sight depth of cloud regions. We found that Serpens Main and Barnard 1 are flattened (sheet-like) at parsec scales, and that all structures have a similar depth into the plane of the sky, on the order of 0.1-0.2 pc. All of these initial results imply that over-dense, sheet-like regions in molecular clouds fragment into filaments, and build up hierarchical structures on the pathway to forming dense cores.


October 28-29, 9:00 to 5:00 pm: Einstein Postdoctoral Fellows will present highlights of their recent work on high energy astrophysics, gravity, and cosmology. Dr. Paul Green is organizing the symposium. For more information, contact him at pgreen@cfa.harvard.edu or at 617-495-7057. Light refreshments will be available. The detailed program and list of speakers can be found at: http://cxc.harvard.edu/fellows/program_2014.html. Phillips Auditorium.

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


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