/_/,/.j/:.?.,L. NASA-CR-200128 Final Technical Report for NASA Grant NAG5-1176 Cooperative Research in High Energy Astrophysics , ,_ /°,,_- Y This grant covered the period July 1989 through April 1994. The research covered a variety of topics including 1. Detectionof cosmic rays and studies of the solar modulation of galactic comic rays 2. Support work for several X-Ray satellites 3. High resolution gamma-ray spectroscopy 4. Theoretical Astrophysics 5. Study of Active Galaxies Details of the research are appended 2. Proposed Joint Effort of the University of Maryland and the NASA Goddard Space Flight Center Laboratory for HiKh Energy Astrophysics This grant supports activities conducted by University personnel both on campus and at the Goddard Space Flight Center. Work will be concentrated in the following areas: I) Detection of cosmic rays and studies of the solar modulation of galactic cosmic rays 2) Support work for several past and upcoming X-ray satellites 3) High resolution gamma-ray spectroscopy of celestial sources 4) Theoretical astrophysics 5) Active galaxies This section describes the work accomplished to date and the proposed joint effort for the next grant period for each of these areas within the overall research program. During the upcoming year, we propose to continue our joint efforts in the areas listed above. 2.1 HiEh Energy Cosmic Rays Cosmic rays are the only samples of matter which reach earth from outside the solar system. As such, they carry information on their origin, acceleration, and subsequent propagation. 2.1.1 Cosmic Ray Detections Past measurements of the flux of antiprotons at low energies is in disagreement with expectations from the best current theory. In an effort to check these measurements, the Low Energy Antiproton experiment (LEAP) was performed as a collaboration between GSFC, University of New Mexico and University of Arizona. The LEAP instrument is a magnetic spectrometer which measures the particle momentum, mass and charge through the use of multiwire proportional counters (MWPC)., a time of flight (TOF) detector and a Cherenkov radiation detector. The LEAP instrument was launched from Prince Albert, Canada, on August 7, 1987. The LEAP instrument had a successful, 22 1/2 hr, flight during Which over i0 million events were recorded. University of Maryland graduate student, Mr. Steven Stochaj, played a major role in the development of the TOF detector and is presently involved with the data analysis. Mr. Stochaj is a co-author of a paper presenting LEAPresults Adv. SpaceRes. (1989) Vol. 9, p. 1265, as well a final paper in preparation. Betweenthe present low energy antiproton measurements,which extend up to about I GeV/nand the higher energy measurementsof Golden (around 5 GeV/n) there are no antiproton measurementsexcept those of Bogom01ov,which have error bars extending over an order of magnitude. Weare planning an experiment (the Isotope Matter-Antimatter Experiment) which will measurethe antiproton fluxes from I00 Mev to about 4 GeV. The experiment will utilize the NASABalloon BorneMagnet Spectrometer (BBMF),three Cherenkovdetectors, and a TOFsystem. The experiment is a collaboration with CalTech andNew Mexico State University. University of Maryland graduate student Shantanu Bhattacharya, whoworked with this group in the summerof 1989, will join the IMAXexperiement whenhe passes his qualifying examin August 1990. Mr. Bhattacharya will be working with this group on preparatory laboratory work for IMAXthis coming summer,1990 as well. Another experiment in which this group is involved is the MASS(Matter- Antimatter Spectrometer) experiment scheduled flight in the spring of 1991. This experiment using the BBMFwill measureantiprotons in the 5 i0 GeV range, as well as making low energy positron measurements. Mr. Glen Allen, a Maryland graduate student, will be working with this group this summer,and is potentially a graduate student on MASS. 2.1.2 Low Energy Cosmic Ray The directional distribution (anisotropy) of energetic charged particles in interplanetary space can provide information on their origin and propagation, and on the structure of the interplanetary magnetic field. The NASA/Goddard Space Flight Center Medium Energy Cosmic Ray Experiment on the ISEE-3/ICE spacecraft has measured the distribution of > i MeV/n and > 5 MeV/n ions since launch in August 1978. However, this data set has been little exploited in the past since it could not be conveniently accessed, lan Richardson has now transferred the complete data base at 15 minutes resolution onto optical disk where it can be accessed via a PC. Software has been written allowing the data to be rapidly reviewed and interpreted. Data from the Goddard instruments on IMP-8 and Helios will also be made available in the future. Changes in particle distributions associated with particle I0 acceleration at interplanetary shocks are being investigated using the ISEE- 3/ICE data and a preliminary study waspresented at the International Cosmic RayConference, Adelaide in January 1990. Studies of the structure of the interplanetary magnetic field include the rapid propagation of solar particles from events on the eastern solar hemisphere in pre-existing magnetic "bottles" extending from the sun, and investigation of the structure of coronal mass ejections using data taken during 1989whenthe spacecraft was off the west limb of the sun. The properties of energetic ions at quiet times are also being studied. Minor activities have included collaboration with Imperial College, Londonon investigations of ISEE-3/ICE energetic particle observations in the geomagnetic tail andat comet Giacobini-Zinner. Papers were also contributed to the International Cosmical Ray Conference on the acceleration of ions at comet Giacobini-Zinner and the spectra of > 35 keV ions in corotating ion enhancements. Hilary Cane's research since early 1989has been mainly directed towards investigating the composition of solar energetic particles. A paper on this topic waspresented at the International CosmicRay Conference. Workhas also continued on attempting to determine the origins of interplanetary disturbances that cause geomagnetic storms. An invited paper on this topic was given at the December1989 AGUmeeting, in collaboration with E. Cliver of AFGL. Future work will combine these efforts as there maybe compositional variations in interplanetary events with different solar origins. 2.2 X-Ray Astronomy James Lochner completed his thesis ("Chaos and Random Processes in the X-ray variability of Cygnus X-I")/ was awarded his Ph.D., and left to take up a postdoctoral position with the X-ray group at the Los Alamos National Laboratory. Personnel now supported by the University of Maryland at the Goddard X-ray group consistent of Dr. Keith Arnaud, as an Assistant Research Scientist, and three graduate students: Damian Christian, Kim Weaver, and Warren Focke. Dr. Keith Arnaud has been instrumental in the establishment of the High Energy Astrophysics Archival Research Center (HEASARC), a collaboration at Goddard between the LHEA and the National Space Science Data Center (NSSDC) The aim of the HEASARC is to make available to US astronomers raw data and II products from previous and forthcoming high energy astrophysics missions along with the software tools to enable this data to be analyzed. The HEASARC subsumesthe ROSATguest observer facility (to be sited at the LHEA)along with the archiving efforts associated with the BBXRTand Astro-D missions. Already the HEASARiCs making available, by electronic means,data from the Einstein Observatory and the ESAEXOSAsTatellites. The addition of the HEAO- I A2 dataset is underway. Arnaud has continued his research on X-ray observations of clusters of galaxies andactive galaxies. With collaborators in England andHawaii he has submitted papers (to MNRASand ApJ, respectively) on X-ray cluster luminosity and temperature functions. The temperature function is particularly.interesting because it can be converted into a mass function and this constrains the primordial perturbation spectrum, f_om which structure in the Universe is assumed to grow. The current results show a slope and normalization for the perturbation spectrum that is inconsistent with the popular cold dark matter model. On the active galaxy front he is involved in several projects to characterize the X-ray spectrum in the energy range of 0.i - 20 keV using Einstein Observatory data. Damian Christian is studying the spectral and temporal behavior of Low Mass X-ray Binaries (I.MXB) under the direction of Dr. Jean Swank. LMXB are among the most luminous X-ray sources known. Their large luminosity is attributed to accretion onto a neutron star from a companion less massive than the sun. An attempt is being made to find the best spectral models that can be applied to a physically reasonable picture for these sources from the analysis of several archive data sets, OS0-8, HEAO-I, and HEAO-2 (Einstein) and the upcoming BBXRT mission. Currently he is involved in the analysis of Solid State Spectrometer (SSS) and Monitor Proportional Counter (MPC) data from the HEAO-2 Observatory. He has completed an extensive recalibration of the SSS. These improvements, along with fitting spectra with the combination of the SSS plus MPC (0.5 20 keV) will determine continuum spectra for nearly 50 I/!XB. In addition to interpreting the physical meaning of continuum models, he is calculating a self consistent accretion disk corona. This calculation, if successful, will help constrain current X-ray observations and will give testable predictions for the upcoming BBXRT mission. He has organized the observation of a dozen I/%XB with BBXRT to look for Fe Line emission, which can be used to further constrain the physics behind these 12 sources_ Kim Weaver has worked on several projects to analyze X-ray spectra of active galactic nuclei. With Drs. Jane Turner, Richard Mushotzky, Steve Holt, and Greg Madejski she has used to Einstein Observatory SSS and MPC spectra to investigate a sample of Seyfert galaxies. Many objects in the sample have spectra that are not consistent with a simple absorbed power-law but require some sort of excess at energies < 1 keY. This excess may be from an accretion disk surrounding the black hole that is hypothesized to lie at the center of active nucleus. This work was presented at the AAS meeting in January 1990 and will shortly be submitted to ApJ. Weaver has also worked with Madejski, Mushotzky and Arnaud on the Einstein Observatory SSS and MPC spectra of B1 Lac objects. This work has confirmed the presence in PKS2155 of a sharp absorption feature at = 0.6 keV as seen by the Einstein Observatory Objective Grating Spectrometer. In addition the same feature has now been found in three other B1 Lacs. This is the only sharp spectral feature observed in B1 Lacs at any wavelength. One interpretation is that this is absorption from warm gas a jet pointing towards us. This work was also presented at the January AAS and is being written up for publication. Warren Focke has been working with Swank on detector developement for the X-ray Timing Explorer (XTE), a collaborative project between Goddard, MIT, and UCSD, due for launch in 1995. He has contributed to the design and construction of the SAA detector and is currently assisting in the calibration and testing of the Proportional Counter Array (PCA), being built by the Goddard X-ray group. The latest results show excellent spectral response (17% at 22 keV) for a xenon-filled counter but some potential background problems. Focke is also working on a project to find out whether HEAO-I A2 data can be used to investigate the Ks iron line seen from the diffuse Galactic emission by the Japanese Ginga satellite. 2.3 Low Energy Gamma-Ray Astronomy The main focus of this research is high resolution gamma-ray spectroscopy of celestial sources in the 20 keV to I0 MeV energy range. The principal experimental objective of this program is to search for and study narrow lines in the low-energy gamma-ray spectrum. Such lines can be produced by i) cosmic ray induced emission from nuclear excited states, 2) remnant 13 radioactivity from nucleosynthesis, 3) positron annihilation, and 4) cyclotron line emission from the strong magnetic field regions near the poles of a neutron star. Observational evidence exists at present for processes 2), 3), and 4). The technique of nuclear spectroscopy applied to astrophysics promises to be a powerful new diagnostic tool for probing high-energy astrophysical processes such as are known to exist in the vicinity of neutron stars and black holes. This is a young field, but already results are in hand that conclusively demonstrate the potency of the method. The principle experimental activity within this program is the development and operation of balloon _ and satellite-borne instrumentation that performhigh-resolution gamma-ray spectroscopy using Germanium detectors. In addition, ground based optical instrumentation is being developed to support the balloon and satellite observations. The individual programs are described briefly as follows: 2.3.1 Gamma-Ray Imaging Spectrometer (GRIS_ GRIS is a very sophisticated and powerful gamma-ray telescope that is nearing its final stages of development. It will be carried above the earth's atmosphere on high altitude balloons. The basic experiment consists of an array of seven large high-purity Germanium detectors to make precise measurements (E/AE - 500) of gamma-ray energies in the 20 keV to i0 MeV range. The detector array is surrounded by a thick massive anti-coincidence shield to suppress the strong atmospheric and instrumental gamma-ray background flux. In addition there is an active Nal coded-aperture mask that will produce gamma-ray images over a 9° x 15 ° field of view. GRIS measures gamma-ray fluxes that are five to ten times weaker than could be detected by the best previous instruments. GRIS was first flown successfully in 1988 from Alice Springs, Australia. Exciting new results were obtained on the Galactic Center arc SN 1987. It will be flown I - 2 times yearly over the next 5 - 6 years. 2.3.2 Transient Gamma-Ray Spectrometer (TGRS) The TGRS is a satellite-borne gamma-ray spectrometer intended to perform high resolution studies of the spectra of gamma-ray bursts. It is planned for flight on the WIND spacecraft that is part of the Global Geospace System (GGS), a new multiple-spacecraft mission to be launched. Its primary purpose 14 is to makethe first precise detailed studies of the lines that are knownto exist in the spectra of gamma-raybursts. Twokinds of lines have been observed. First, lines in the vicinity of 50 keV occur in manybursts. They are believed to result from electron cyclotron emission in the enormous magnetic fields (1012) gauss that are typically present at the poles of neutron stars. Second, lines in the vicinity of 400 keVhave been observed in 10%of the bursts. These are believed to be due to electron-positron annihilation (511 keV) radiation produced near the surface of a neutron star. This radiation is subsequently redshifted as it escapes the strong neutron star gravitational field. If this is true then it represents the first direct measurementof the gravitational potential of a neutron star. The basic instrument consists of a single Germaniumcrystal radiatively cooled to a temperature of 95K. The detector is unshielded and Dearly omnidirectional as the gamma-rayburst maycomefrom any randomdirection in the sky. It will makespectral measurementswith typically 40 times better energy resolution than the best previous instrument. 2.3.3 Rapidly Moving Telescope (RMT) RMT is a ground based optical telescope capable of slewing to any target on the sky in less than one second, tracking the target with sub-arcsecond stability, and imaging it with one arcsecond resolution. It can see objects as faint as 15-th magnitude with one second exposures. Its purpose is to locate and identify the optical counterpart flash to Gamma Ray Burst events. It will operate in conjunction with the MIT Explosive Transient Camera. The RMT instrument is able to move so quickly, because unlike a traditional telescope, only the mirror assembly moves (an azimuth-elevation mechanism); thereby picking out a patch of the night sky and reflecting it into a fixed telescope. Imaging is done with a CCD camera. The instrument is designed to operate totally automated. The observing program and data analysis is all computer controlled. Currently the instrument is undergoing integration and shakedown operation at the Goddard Optical Test Site. After this initial trial operation, it is expected to be installed at its permanent location at Kitt Peak, AZ around May 1989. 15 2.4 Theoretical Astrophysics Theoretical studies are essential in order to determine the most important directions topursue in future measurements, the interpretation of existing observations within a self-consistent framework, and in the development of new experimental techniques. Theoretical research is pursued in x-, gamma- and cosmic ray astrophysics, as well as in extragalactic astronomy, cosmology compact object astrophysics, and solar physics. Research relevant to x- and gamma-ray astrophysics is carried out by Drs. Harding, Kazanas, Kallman, and Ramaty. Drs. Jones and Perko are pursuing a program in cosmic ray astrophysics with particular emphasis on acceleration and solar modulation problems. Particular emphasis is given to the physics and radiation mechanisms in compact sources both on stellar and galactic scales, such as pulsars and active galactic nuclei. A significant fraction of this research is the study of gamma ray spectroscopy associated with e+e" annihilation lines, both in active galactic nuclei (including the galactic center) and in gamma ray bursts (Drs. Ramaty, Kazanas, and Harding). Research in high energy radiation from pulsars, with particular emphasis on processes in superstrong magnetic fields, is conducted by Dr. Harding, and R. Preece, a graduate student. Dr. Kazanas is modeling the emission of similar radiation from active galactic nuclei with P. Giovanoni, a graduate student, with particular emphasis on the observational effects of relativistic neutrons on the spectrum of these objects. It has in fact been shown that the latter particles could indeed have unique signatures, which are apparently present in the spectra of "radio loud" active galaxies. Dr. Kallman is examining in detail the physics of broad emission line clouds of the latter objects and also the UV and optical line radiation associated with compact galactic x-ray sources. Also in collaboration with K Ko, a graduate student, they are studying the effects of X-ray irradiation on the structure and the dynamics of accretion disks in galactic X-ray sources Dr. Harding, in collaboration with Drs. Gaisser and Stanev of the Baruoi Research Foundation, is examining the possible gamma-ray signatures due to particles accelerated by the pulsar (compact remnant) of SN 1987A upon their interaction with the supernova ejecta. Research pertaining to cosmology and the interplay between the latter discipline and particle physics is performed 16 by Dr. Stecker in collaboration with Dr. Shafi of the Bartol Research Foundation. This research emphasizesthe impact that our knowledgeof high energy physics has on understanding the largest scale features of the universe, such as the formation of the large scale structure, the nature of the unseen (dark) matter in galaxies and clusters of galaxies, the fluctuations of the microwavebackground, and the production of matter- antimatter asymmetryin the universe. Solar flare research is carried out by Drs. Kozlovsky, Ramaty, andJ. Miller, a graduate student, emphasizing particle acceleration and_transport of the gamma-rayline and neutron production in these events as well as interpretation of data from the Solar MaximumMission. 2.5 Active Galaxies Zlatan Tsvetanov has studied the ionizing radiation field in Seyfert galaxies by means of observing spatially resolved phenomena. Two observational techniques explored -- narrow band emission-line imaging and long-slit spectroscopy. Images centered on redshifted positions of [0111]_5007, H= and adjacent continua are used to obtain "pure" emission-line maps as well as ionization and/or reddening, maps. There permit the study of both general morphologyand angular distribution of the ionizing flux. Long- slit spectroscopy, on the other hand, provides important information for the ionizing mechanism (line-ratio diagrams) and for the study of the velocity field. In addition to the observational approach a powerful photoionizing code is used to model the line ratios as a function of position. Observations Two observing runs were completed successfully in this period. Four nights were awarded in January 1990 at the 2.5 m INT telescope at La Palma Observatory for detailed long-slit spectroscopy. This project is in collaboration with I. Perez-Fournon and J. M. Rodriguez-Espinosa (IAC) and A Wilson (UMD). The objects were selected so that emission-line maps could be used to guide the slit positions to' cover effectively extended emission region. Weather conditions were relatively good and permitted the fully complete observation of two objects. Entire extended narrow-line regions (ENLR) of both NGC 3516 and Mkn 3 were covered by a grid of high resolution spectra (to study the kinematics of the emitting gas) and a number of medium 17