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2005 Annual Report

II. Research

A few of the research activities were sufficiently newsworthy to be Press Releases:

• "Close to Black Holes' Edges, Scientists Make Two Discoveries",
  NASA/GSFC press release (2005 Jan) and led by JCA-affiliate T.Jane Turner and also featuring the work of Ian George [Links];
• "New Image of Earth, seen through Gamma-ray Eyes",
  NASA/GSFC press release (2005 Mar) featuring the work of Dirk Petry (which was also the lead article on NASA's "Looking at Earth" WWW page for a while), [Links] ;
• "Three satellites needed to bring out 'shy star'",
  ESA, UMBC & Univ. Geneva press releases (2005 Oct) featuring the work of Volker Beckmann [Links].

The contributions of individual members are (briefly) summarized below .

David Band was actively involved with a number of research projects of the past year. He and Rob Preece (NSSTC) tested two proposed relations between characteristic gamma-ray burst energies (the 'Amati' and 'Ghirlanda' relations) using an extensive catalog of bursts from the CGRO/BATSE detector, and found the bursts to be inconsistent with the Amati relation and marginally consistent with the Ghirlanda relation. An extension to this results is underway. Band is also assisting Mike Stamatikos (Graduate student at Univ. Wisconsin, Madison) studying the upper limits the AMANDA neutrino experiment places on gamma-ray burst emission of neutrinos, by providing gamma-ray burst data from the CGRO/BATSE detector, and will be a co-author on the resultant paper(s). With Andy Buffington (UCSD), Band determined upper limits on the optical emission from 58 -ray bursts in the hour after the burst occurred using the Solar Mass Ejection Imager. While these limits are not particularly sensitive (~10th magnitude), for many bursts they provide the only constraints on the early optical afterglow. Band also extended his methodology evaluating the sensitivity of gamma-ray burst detectors by considering temporal effects, and applied this methodology to understand the sensitivity of the Swift mission using the on-orbit calibration. He showed that the trigger increases the sensitivity to long duration bursts relative to previous detectors such as CGRO/BATSE. As part of the team designing the EXIST mission concept, Band has also been using this methodology in determining the burst detection properties of the proposed EXIST design.

Volker Beckmann continued working on INTEGRAL-related science as well as on Swift data. The research included the compilation of the first INTEGRAL AGN catalog. A publication about this work is in press, and the results presented at the "X-ray Universe" conference in El Escorial (Spain) in September. Beckmann also completed a detailed study of NGC 4151 using INTEGRAL data which has now been published in ApJ, and was presented at the "INTEGRAL Science Workshop" (ESA/ESTEC,January 2005). Links]. In another project, Beckmann investigated members of the class of newly detected highly-absorbed High-Mass X-ray Binaries (HMXB). For the data analysis he applied successfully for a Swift ToO observation and combined data from INTEGRAL, Swift, RXTE, and Spitzer to reveal the nature of the source IGR J16283-4838, detected by INTEGRAL in April. The results were also the topic of a press release, simultaneously issued by UMBC, ESA, and the University of Geneva (see above). This work was therefore recognized by several newspapers and news agencies around the world [Links].

Patricia Boyd was a co-author in four refereed papers associated with gamma-ray bursts detected by Swift, and worked on several similar papers in preparation. Patricia Boyd left the JCA in 2005 November to take up a civil service position at NASA/GSFC. [No detailed report received]

John Cannizzo continued carrying out testing and research with a computer model he wrote which calculates the 3D evolution of a relativistic fluid. This was applied to the fluid ejecta that produces a gamma-ray burst. He is currently testing analytical solutions of the relativistic Sedov-Taylor solutions (from Blandford & McKee) that characterize the evolution of a spherical blast wave. In the past few months he has been comparing results with the relativistic adaptive mesh solver in the FLASH code from the Univ. Chicago ASCI Center. A great deal of effort went into developing an algorithm for LIGO data analysis using the Hilbert-Huang transform. Extensive codes were written for this analysis. Work also continued with Cannizzo's time dependent accretion disk code, in investigating the nature of the Z Cam stars, and continuing work on the depletion of terrestrial ozone from gamma-ray bursts. Cannizzo's research on Swift involving short gamma-ray bursts garnered several press releases and was the featured topic of the UMBC Dept. of Physics "Spotlight-On" WWW page for some time.

James Chiang is working (for UMBC) at the Stanford Linear Accelerator Laboratory (SLAC) as part of the GSSC within the California-Harvard Astrostatistics Collaboration. With D. van Dyk (Statistics, UC Irvine), he is applying Bayesian methods to do image reconstruction/PSF deconvolution of CGRO/EGRET and GLAST data. He is also collaborating with J.-L. Starck (Saclay) and S. Digel (SLAC) on the use of wavelet-based denoising techniques to ?-ray data for source dectection and identification. Chiang is also collaborating with R. W. Romani (Physics, Stanford Univ.) on blazar emission models and blazar luminosity function estimates based on CGRO/EGRET data. These investivations will be used to measure the extragalactic background light in the near IR using GLAST blazar observations. He is working with L. Wai, E. Bloom, T. Baltz (SLAC) on models of gamma-ray emission from WIMP annihilation in dark matter distributions from the Galactic center and dwarf spheroidal galaxies in the Local Group. With T. Kamae and J. Cohen-Tanugi (SLAC), Chiang is working on modeling and analyses of high-energy emission from supernova remnants such as RXJ1713.7-3946.

Dave Davis and Mark Henriksen are re-analysing the Chandra ACIS-I data for the diffuse gas in the bimodal cluster, Abell 222-Abell 223. The analysis is alsmost complete, and a papper being written. Preliminary results were also presented at the "6 Years of Chandra Science" meeting in November. Davis also worked on science proposals for Chandra and XMM-Newton, and Suzaku observations.

This year, JCA-affiliate Markos Georganopoulos proposed a method for measuring the elusive matter content (electron-proton vs pair plasma) of quasar jets using Comptonization of CMB photons. This method was immediately used by another group to set the first limits on the jet matter content. Georganopoulos was involved in several projects in collaboration with JCA-affiliate Eric Perlman, and also continued work on the deceleration of relativistic jets, arguing that the TeV emission of the radiogalaxy M87 strongly supports deceleration at ~pc scales. A new synchrotron-Compton emission code is under development (with Perlman) will soon be made publicly available through the web, both on a UMBC page as well as through the GLAST/LAT webpages. As part of this work, Georganopoulos & Perlman have discovered that (contrary to previous sugggestions) SSC emission naturally produces superquadratic variability.

Ian M. George continued his collaborative studies of Seyfert galaxies using Chandra, XMM-Newton, HST and FUSE data. With T.Jane Turner (UMBC/JCA who is the lead on the project), B. Wingett (UMBC Grad. Student), L. Miller (Oxford Univ.) and J. Reeves (JHU & NASA/GSFC), he helped in the development of a new method of examining X-ray data from Seyferts using intensity maps in the energy-time plane, and the application of Principal Component Analysis. Together, these new techniques have yielded insight into the correct deconstruction of the complex spectra of many Seyfert galaxies and hence identify the true origin of some components of emission. In the case of the XMM-Newton data from Mrk 766, application of these techniques led to the detection of components of the Fe Kalpha emission line which varied in energy and time in a manner consisent with that expected from hot-spots on an accretion disk very close to the putative black hole. These results led to a press release (above) and to a 500ks follow-up observation of the target. Work continues on the new, longer XMM-Newton data set. George made contributions to a number of other papers, and a major contribution to a paper interpreting the ionized-absorbers in the Seyfert galaxy NGC 4151 as detected by high-resolution HST, FUSE and Chandra/HETGS spectra (led by S. B. Kraemer of CUA).

In addition to the work with Davis outlined above, Mark Henriksen collaborated with Danny Hudson (Bonn Univ, former UMBC Graduate student) in a study of the non-thermal emission from Abell 262 using RXTE. Time was awarded on the Giant Metrewave Radio Telescope (GMRT) to study 3 merging clusters (collaboration with Gopal-Krisna of the Tata Institute). Work continued on a data mining/image classification algorithm project with Eric Tittley (RoE) whereby the complex central morphology of clusters are characterized graphically, then grouped using the support vector machine learning technique.

Masaharu Hirayama started a work to evaluate effectiveness of GLAST observing strategies for pulsar studies, including estimation of pulse detection sensitivity in a particular observation mode. Specifically the goal is to understand scientific benefits from pointed observations of pulsars, compared with a continuous coverage by an all-sky scanning observation. The work is in progress, but not yet at a stage where significant scientific results can be obtained.

Kip Kuntz continued his study of the nearby face-on galaxy M101 using a 1Ms exposure obtained with Chandra. He has found that the spectrum of the diffuse emission is remarkably uniform, suggesting that the brightest regions have the same combination of emission mechanisms as the dimmer regions. The similarity of the spectra of late-type spiral galaxies, nearly all disks have temperatures of kT~0.25 - 0.6 keV appears to be due to the lack of spectral resolution. The ratio of the emission measures of the two thermal components seems to depend on Hubble type rather than specific star formation rates; earlier type galaxies seem to be "hotter". Kip Kuntz left the JCA in 2005 February to take up a position at JHU.

Irena Malkova is no longer a member of the JCA. [No detailed report received]

Igor Moskelenko left the JCA in 2005 June to take up a position at Stanford University. [No detailed report received]

Julie McEnery left the JCA in 2005 August to take up a civil service position at NASA/GSFC. [No detailed report received]

JCA affiliate Eric Perlman continues his work on the physical nature of jet emissions from AGN. He showed that spectral curvature does exist in the X-ray spectra of BL Lac objects, presented an in depth look at the X-ray morphology and spectral structure of the M87 jet, and showed that the X-ray spectral curvature seen in both BL Lac objects and in M87 requires either an intermittent particle acceleration mechnism, or one that only operates in a small fraction of the jet at any one time. Perlman also worked heavily on the discovery of several new jets in the optical/IR and X-rays including as a member of one of the Chandra jet survey teams. Perlman is now working on HST polarimetry and Chandra imaging of an additional six radio galaxy jets, hoping to look at issues such as energetic and magnetic field structure and their relation to high-energy emissions. Perlman also continues his work on the physics of high-power blazars along with members of the DXRBS team. Most recently they have addressed the radio properties of X-ray loud flat-spectrum quasars on kpc scales and are doing further work to quantify their structure on VLBI scales. Perlman and collaborators used an eclipse of the accretion disk of the quasar 3C279 by a cloud in its narrow-line region, to estimate the size of its accretion disk. The estimate derived (23 AU, or 12 Schwarzchild radii for a 10⁸ solar mass black hole) constitutes an important confirmation of thermal disk models. He has also expanded his work into the properties and physics of AGN tori, using mid-IR observations, with papers on the Circinus galaxy, NGC 1068, and work that is currently in progress on mid-IR observations of M87 and Cyg A. This will form an increasing fraction of Perlman's work in future, as he has been selected as a member of the CanariCam Science Team, a key projects team with guaranteed time on the 10.4m Gran Telescopio Canarias, scheduled to see first light in 2006.

In terms of research not connected to the programmatic work on the GLAST mission, Dirk Petry continued to contribute to publications by the VERITAS collaboration on ground-based Cherenkov astronomy. Dirk Petry left the JCA in 2005 December to take up a position at Iowa State University [No detailed report received]