6 NASA-CR-202364 C AL-2572 /z//uN” L National Aeronautics and Space Administration / p- gq-c-a FINAL TECHNICAL REPORT FOR NAS 5-32063 6 fJ- 5y2dp.$& Submitted to: National Aeronautics and Space Administration Goddard Space Flight Center Greenbelt Road Greenbelt, MD 20771 Submitted by: The Trustees of Columbia University in the City of New York 351 Engineering Terrace New York, New York 10027 Prepared by: Columbia Astrophysics Laboratory Departments of Astronomy and Physics Columbia University 538 West 120th Street New York, New York 10027 Principal Investigator: David J. Helfand 8 Title of Research: “A Complete Public Archive for the Einstein Imaging Proportional Counter” Period of Covered by Report: 24 September 1992 - 23 September 1996 October 1996 Final Technical Report for NASA NAS5-32063: “A Complete Public Archive for the Einstein IPC” David J. Helfand Abstract Consistent with our proposal to the Astrophysics Data Program in 1992, we have completed the design, construction, documentation, and distribution of a flexible and complete archive of the data collected by the Einstein Imaging Proportional Counter. Along with software and data delivered to the High Energy Astrophysics Science Archive Research Center at Goddard Space Flight Center, we have compiled and, where appro- priate, published catalogs of point sources, soft sources, hard sources, extended sources, and transient flares detected in the database along with extensive analyses of the instru- ment’s backgrounds and other anomalies. We include in this document a brief summary of the archive’s functionality, a description of the scientific catalogs and other results, a bibliography of publications supported in whole or in part under this contract, and a list of personnel whose pre- and post-doctoral education consisted in part in participation in this project. I. Project Goals and Achievements A. The archive software. The goal of our proposal “A Complete Public Archive for the Einstein IPC” was to provide for the community a flexible archive and analysis system. The need for such a system has been apparent for some time, and the progress made at Columbia over the past ten years in understanding and characterizing fully this ground-breaking X-ray astronomy instrument, coupled with the enormous advances in computing power since the original mission, make such a system both desirable and practical. The continued interest and scientific value of the IPC data is apparent from the publication statistics compiled by Dr. F.D. Seward at the Smithsonian Astrophysical Observatory: in 1990 alone, 13 years after the launch (and 9 years after the demise) of the mission, 91 papers using Einstein data appeared in the literature. With the advent of several new X-ray missions in the 1990s (two in progress and four more to come), the value of these archival data will only increase. Placing the powerful Columbia analysis system in the public domain under the aegis of the HEASARC offers permanent access to this important dataset. This primary goal was accomplished by last fall. After extensive interaction with HEASARC personel, we completed the transfer of the full IPC archive along with a doc- umented set of software which provides for the user a suite of flexible tools with which to derive fluxes and upper limits for any celestial position covered by the 4082 pointings 1 conducted during the mission. The tools include the flat-fielding algorithm developed at Columbia to correct IPC images for the substantial 1-30 arcminutescale features in the response of the instrument which seriously compromised some early analysis efforts. A hypercube of flat-fields derived from the full, sourcesubtracted dataset is invoked when an image is to be analyzed, and a customized flat-field corresponding precisely to the editing criteria used on the image is applied (an option for the user to employ the global flat field using all energy channels and aspect criteria is offered for cases in which the data-editing flags applied to the image produce a corresponding flat field with insufficient statistical precision). Since the user may select from all possible energy ranges, aspect qualities, and viewing geometries in any combination, complete flexibility is achieved. The source search algorithm used for analyzing a selected, flat-fielded image can per- form a source search of a single field or to a user-specified threshold over the entire dataset. A complete description of the algorithm is provided in our paper “The Einstein Two-Sigma Catalog” (Moran et al. 1996) which was published in the Astrophysical Journal last April. Further details of the many enhancements we have made to the database and analysis system may be found in that paper and/or in last year’s annual report. We have applied this algorithm to the entire dataset and compiled, as we originally proposed, a number of definitive source catalogs which we describe in the next section. The HEASARC personnel have indicated they are satisfied with the level of documen- tation of both the data and the analysis software, and it is now in their hands, as specified in the contract, to provide access to the user community. B. Data products. Using our IPC analysis system, we have, as proposed, constructed a number of defini- tive catalogs from the pointed IPC database. These include: 0 The twesigma catalog, containing over 46,000 entries, more than triple the number of real celestial X-ray sources in the original SA0 IPC catalog. The utility of this catalog is demonstrated in Moran et al. (1996) where we show how crosscorrelation of this data product with catalogs from other wavelength regimes can yield important new discoveries such sa several high-z quasars up to z = 4.3 (no quasars with z > 2.9 were found in the Einstein Medium Sensitivity Survey). A reprint of the paper is included in the Appendix where much greater detail on both the algorithms and the science emerging from their application can be found. 0 Hard and Soft source catalogs were also produced as a byproduct of the two-sigma catalog creation process, although the latter required the invention of an automated technique for filtering our spurious sources detected in regions of extended emission. The results are presented in two Columbia PhD Dissertations (Moran 1994 and Yan- copoulos 1996); the soft search has led to the identification of several candidates for 2 isolated neutron stars accreting from the ISM on which followup observations are continuing. An Einstein extended Source Survey (EXSS) has just been completed (Oppenheimer et al. 1997). A total of 321 previously unidentified discrete sources ranging in size from 2-10 arcminutes has been catalogued, and optical followup observations indicate that many are indeed unrecognized clusters of galaxies. A preprint describing this work may be found in the Appendix. A Burst Catalog was also published this year, describing a complete search of the IPC database for short-timescale (1-30 seconds) flashes in the X-ray sky (Gotthelf et al. 1996). While several dozen such events were detected and they defy all attempts to asssociate them with environmental or instrumental anomalies, we remain skepti- cal that they are truly astrophysical phenomena. Nonetheless, their relatively small number has allowed us to tighten substantially existing constraints on Galactic halo models for gamma ray bursts. Diffuse X-ray emission maps have also been derived from the IPC database and pub- lished in the literature. In addition, we recently demonstrated the utility of these data by analyzing the crosscorrelation between faint galaxy counts and the IPC arcminute background fluctuations, detecting the signal on this scale for the first time and dis- covering a non-zero correlation amplitude out to scales of - 10’ (Refregier et al. 1997; preprint attached). Thus, we have acheived all of the goals laid out in our proposal for creating and publishing useful data products from the IPC archive using our flexible analysis system. 11. Bibliography The work reported in the following papers was supported in whole or in part by the funding received under this NASA contract. Reprints or preprints are included in the Appendix. “The Einstein Observatory Detection of Faint X-ray Flashes,” 1996, E.V. Gotthelf, T.T. Hamilton, and D.J. Helfand, ApJ, 466, 779. “The Absence of X-ray Flashes From Nearby Galaxies and the Gamma-Ray Burst Distance Scale,” 1996, T.T. Hamilton, E.V. Gotthelf, and D.J. Helfand, ApJ, 466, 795. “The Einstein Two-Sigma Catalog: Silver Needles in the X-ray Haystack,” 1996, E.C. Moran, D.J. Helfand, R.H. Becker, and R.L. White, ApJ, 461, 127. “Detailed Analysis of the Cross-Correlation Function between the X-ray Background and Foreground Galaxies,” 1996, A. Refregier, D.J. Helfand, and R.G. McMahon, ApJ, 477 (Mar 1, 1997, in press). 3 “A Survey of the Einstein IPC Database for Extended X-ray Sources,” 1996, B.R. Oppen- heimer, D.J. Helfand, and E.J. Gaidos, ApJ (submitted). “Silver Needles in the Two-Sigma Haystack: Galaxies, Clusters, and the XRB,” 1993, in Observational Cosmology, ed. G. Chincarini, A. Iovino, T. Maccacaro, and D. Macagni, ASP Conf. Ser. 51, 470. “Isolating the Foreground of the X-ray Background,” 1996 A. Refregier, D. J. Helfand and R.G. McMahon in Rontgenstralung from the Universe, ed. H.U. Zimmermann, J.E. Trumper, and H. Yorke, p337. “Neutron Stars in Binaries and in Isolation,” 1996 S. Yancopoulos PhD. Dissertation, Columbia University, Chapter 4. “Dansient X-ray Phenomena in Astrophysics,” E.V. Gotthelf, PhD. Dissertation, Columbia University, Chapter 3. 111. Personnel During the four years that this contract was in effect, a number of undergraduate students, graduate students, and postdoctoral fellows contributed substantially to the work involved and, in turn, received a significant fraction of their research education under the contract’s sponsorship.