Astrophysics Science Division Colloquium Series
Schedule: January - March 2008

Astrophysics Science Division Colloquium Series
Schedule: January - March 2008

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Through the courtesy of the speakers since 2004, most presentations are available on line. Future schedules: 2008, Second Quarter

Past schedules: 2007, Fourth Quarter 2007, Third Quarter 2007, Second Quarter 2007, First Quarter 2006, Fourth Quarter 2006, Third Quarter 2006, Second Quarter 2006, First Quarter

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Time: 3:45 pm (Meet the Speaker at 3:30 pm) - Location: Bldg 21, Room 183 - unless otherwise noted.
To view the abstract of a seminar, click on the title.

January
Sunday	Monday	Tuesday	Wednesday	Thursday	Friday	Saturday
		1 No Talk (Holiday)	2	3	4	5
6	7	8 No Talk (AAS)	9	10	11	12
13	14	15 Adrienne Juett (NASA/GSFC NPP) - X-raying the Interstellar Medium	16	17	18	19
20	21	22 Ted Gull (NASA/GSFC) - Eta Carina - What we know and what we will test	23	24	25	26
27	28	29 Eli Dwek (NASA/GSFC) - SN1987A X-ray and IR analysis of the "big crash"	30	31
February
Sunday	Monday	Tuesday	Wednesday	Thursday	Friday	Saturday
					1	2
3	4	5 No Talk	6	7	8	9
10	11	12 Nick Sterling (NASA/GSFC NPP) Measuring the Abundances of Exotic Elements in Planetary Nebulae	13	14	15	16
17	18	19 James Battat (SAO) The Apollo LLR project	20	21	22	23
24	25	26 Richard Kelley (NASA/GSFC) - The NEXT SXS Mission	27	28	29
March
Sunday	Monday	Tuesday	Wednesday	Thursday	Friday	Saturday
						1
2	3	4 Cole Miller (UMCP) - Black Hole Kick Predictions	5	6	7	8
9	10	11 Margaret Hanson (U Cincinnati) - One Hundred 30 Dors: Is the Milky Way Different or Are We Somehow Missing Them?	12	13	14	15
16	17	18 Dennis Bodewits (NASA/GSFC) - Cometary X-rays	19	20	21	22
23	24	25 No Talk	26 Mark Trodden (Syracuse) - Cancelled	27	28	29
30	31

X-raying the Interstellar Medium Adrienne Juett NASA/GSFC NPP Tuesday, January 15, 2008 Abstract We have used photoelectric absorption features in the Chandra/HETGS spectra of bright X-ray binaries to study the detailed spectroscopic structure of oxygen, iron, and neon absorption in the interstellar medium (ISM). This is the highest-resolution X-ray spectral study of interstellar absorption ever performed, revealing previously undetected features and demonstrating the inadequacy of existing models for grating data. We find that the ISM absorption edges are well described by the neutral, atomic cross-section calculations and laboratory measurements, although requiring small (<50 mA) shifts to the wavelength scales. The high-resolution spectra allow us to make an independent determination of the relative abundances of the elements. The K-shell edges of oxygen and neon also include absorption lines from singly and doubly ionized forms; we are able to measure the large-scale ionization fractions of oxygen and neon in the ISM. Finally, we will present new results from a comparison of the ultraviolet and X-ray absorption properties of the ISM. The combined data allows us to determine the abundances relative to hydrogen and constrain the depletion of metals without using the abundance assumptions inherent in ultraviolet only studies.

Eta Carina - What we know and what we will test Ted Gull NASA/GSFC Tuesday, January 22, 2008 Abstract Eta Carina is a massive binary wind system with historical ejecta that originated from at least one of the companions at the end of its hydrogen-burning phase. The binary undergoes X-ray and spectroscopic minima every 5.54 years with the next minimum predicted to be in mid-January 2009. We intend to gather observations before, during and after this minimum to test models of the winds and the massive ejecta thrown out in two observed events in the 19th century. Moreover, the N-rich, C- and O-depleted ejecta includes abundant lines of metals including V, Sr and Sc. Why? What dust formed with a paucity of C and O? Ultimately how much mass has been ejected and does this system provide insight to the massive progenitors of the long GRBs?

SN1987A X-ray and IR analysis of the "big crash" Eli Dwek NASA/GSFC Tuesday, January 29, 2008 Abstract Multiwavelength observations of supernova remnant (SNR) 1987A show that its morphology and luminosity are rapidly changing at X-ray, optical, infrared, and radio wavelengths as the blast wave from the explosion expands into the circumstellar equatorial ring (ER), produced by mass loss from the progenitor star. The Infrared emission arises from dust particles in the ER that are collisionally-heated by the X-ray emitting plasma. In this talk I will present combined IR and X-ray observations of the interaction between the SN blast wave and the ER, and show what we can learn from the evolution of the IR-to-X-ray flux ratio about the physical conditions of the X-ray emitting plasma and the interaction of the dust particles with the hot gas. Multiwavelength observations of supernova remnant (SNR) 1987A show that its morphology and luminosity are rapidly changing at X-ray, optical, infrared, and radio wavelengths as the blast wave from the explosion expands into the circumstellar equatorial ring (ER), produced by mass loss from the progenitor star. The Infrared emission arises from dust particles in the ER that are collisionally-heated by the X-ray emitting plasma. In this talk I will present combined IR and X-ray observations of the interaction between the SN blast wave and the ER, and show what we can learn from the evolution of the IR-to-X-ray flux ratio about the physical conditions of the X-ray emitting plasma and the interaction of the dust particles with the hot gas.

The Apollo LLR project James Battat Smithsonian Astrophysical Observatory Tuesday, February 19, 2008 Abstract TBD

Measuring the Abundances of Exotic Elements in Planetary Nebulae Nick Sterling NASA/GSFC Tuesday, February 12, 2008 Abstract In recent years, trans-iron elements have been detected in the UV, optical, and IR spectra of more than 100 planetary nebulae (PNe). These "neutron(n)-capture" elements are of particular interest because they can be produced by s-process nucleosynthesis in the asymptotic giant branch (AGB) progenitors of PNe. Most of the n-capture elements that have been detected in PNe are not accessible in the spectra of evolved stars, and hence nebular spectroscopy provides a unique opportunity to study enrichments of these species in one of their sites of synthesis for the first time. Accurately determining the abundances of these species in PNe also provides important new constraints to models of AGB star structure and nucleosynthesis, particularly the efficiency of convective mixing and dredge-up and the physical conditions under which s-process nucleosynthesis occurs. I will review recent UV and IR studies of s-process enrichments in PNe, in which the abundances of Ge, Se, and Kr were determined in over 100 PNe. In addition, I will discuss an ongoing project to obtain deep, high-resolution optical spectra of PNe in order to detect multiple ions of Kr and several other n-capture elements (including Br, Xe, and Rb). Because of the low cosmic abundances of n-capture elements (< few 10^-9 that of H), many challenges exist in the analysis of their spectroscopic features. Foremost among these challenges are the weakness of emission lines from these species, which causes only one or two ions from each of these elements to be detectable in most PNe. It is therefore important to accurately estimate the abundances of unobserved ionization stages, a goal that requires accurate data for atomic processes affecting the ionization balance - data which is currently unknown for nearly all n-capture elements. I will discuss ongoing experimental and theoretical efforts to determine the photoionization cross-sections and rate coefficients for various recombination processes for ions of the four most widely observed n-capture elements in PNe (Se, Kr, Xe, and Ge). These new atomic data will be incorporated into state-of-the-art photoionization codes in order to model the ionization structure of n-capture elements observed in ionized nebulae, and accurately determine their abundances.

The NEXT / SXS Mission Richard Kelley NASA/GSFC Tuesday, February 26, 2008 Abstract The Japan Aerospace Exploration Agency's (JAXA) New Exploration X-Ray Telescope (NEXT) is now under development for launch in 2013. The observatory is designed to provide extremely high spectral resolution with large collecting area below 10 keV using an x-ray calorimeter and a very large band pass (up to 300 keV) with extraordinary sensitivity over the range 10-80 keV using focusing x-ray optics. In this talk I will give an overview of the mission and discuss plans for the Soft X-Ray Spectrometer (SXS), which uses an x-ray calorimeter array to provide the high spectral resolution. The SXS will use a 6x6 calorimeter array that has strong heritage in the Suzaku program with better than 7 eV energy resolution, and probably as good as 4-5 eV expected based on recent laboratory tests. The cryogenic system will be a hybrid design developed by ISAS/JAXA with both liquid helium and mechanical coolers to provide a robust, redundant system with long life (> 3 years). The x-ray optical system uses thin-foil conical optics to provide at least 220 square cm at 6 keV. The SXS will enable a wide variety of interesting science topics to be pursued, including testing theories of structure formation using velocity measurements of clusters of galaxies and inferring the energy output from the jets and winds of active galaxies. The SXS will accurately measure metal abundances in the oldest galaxies, providing unique information on the origin of the elements, and observe matter in extreme gravitational fields, enabling time-resolved spectra from material approaching the event horizon of a black hole.

Black Hole Kick Predictions Cole Miller University of Maryland College Park Tuessday, March 4, 2008 Abstract TBD

One Hundred 30 Dors: Is the Milky Way Different or Are We Somehow Missing Them? Margaret Hanson U. Cincinnati Tuesday, March 4, 2008 Abstract There are a few ways to estimate the number of massive open clusters expected in the disk of the Milky Way, such as the total star formation rate of the Galaxy, or the open cluster mass function extrapolated to include the entire Galaxy. Surprisingly, they give similar predictions: the Milky Way should contain about 100 clusters as massive as 30 Doradus in the Large Magellanic Cloud, and even several clusters with 10 times that mass. Why donÕt we see them? This talk will first look closely at these predictions and compare that to what we have found so far in our Galaxy. I will then present sophisticated Monte Carlo imaging simulations our group is doing to estimate the selection biases faced by current near-infrared searches for these massive clusters.

Cometary X-rays Dennis Bodewits NASA/GSFC NPP Tuesday, March 18, 2008 Abstract The interaction of the solar wind with the planets, moons and the interstellar medium is of key importance for understanding the evolution of our solar system. The interaction with Earth’s atmosphere is best known for the northern light. In case of Mars, the interaction with the solar wind might have lead to the erosion of its atmosphere. Solar wind-atmosphere interactions can be studied particularly well in cometary atmospheres, because in that case the solar wind flow is not attenuated by a planetary magnetic field and interacts directly with its atmosphere, the coma. When solar wind ions fly through an atmosphere they are neutralized via charge exchange reactions with the neutral gaseous species. These reactions depend strongly on target species and collision velocity. The resulting X-ray and Far-UV emission can therefore be regarded as a fingerprint of the underlying reaction, with many diagnostic qualities. This seminar will address all aspects relevant for X-ray and FUV emission from comets: experimental studies of state-to-state charge exchange cross sections, observations of X-ray emission from comets using Chandra, XMM, and Swift, and theoretical modeling of the interaction of solar wind ions with cometary atmospheres and the resulting X-ray emission spectrum.

Cancelled Mark Trodden Syracuse University Wednesday, March 26, 2008 Abstract Talk Cancelled

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Randall Smith