Symposium Proceedings

Software and Calibration

On-orbit Performance of the Suzaku X-ray Imaging Spectrometer

Mark Bautz (MIT Kavli Institute) Suzaku XIS Team

The X-ray Imaging Spectrometer is the CCD imager aboard Suzaku, the X-ray obsevatory launched by the Institute of Space and Astrophysical Sciences of the Japan Aerospace Exploration Agency in July, 2005. We characterize the initial on-orbit performance of the instrument, compare its capabilities with those of Chandra and XMM/Newton, and present representative results from the early phase of mission.

Error Analysis of HRC-I ECF Regions Applied to ACIS Data

Eli Beckerman, Diab Jerius (SAO)

In order to determine the errors associated with using HRC-I ECF tables on ACIS data, we raytrace a grid of off-axis observations with both HRC-I and ACIS-I at the aimpoint. We use two different approaches to determine the impact of using HRC-I ECFs on ACIS data. First, we compare the radii at which specific enclosed count fractions are reached on HRC and on ACIS. Second, we apply the HRC ECF regions to ACIS data and study the relative enclosed count fractions at those radii.

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New Features in ACIS Extract, a Semi-automated Package for ACIS Source Extraction and Spectral Fitting

Patrick Broos, Leisa Townsley, Konstantin Getman (Penn State Univ.)

We present examples of new features and facilities in ACIS Extract (AE), the IDL-based software package that helps to automate the extraction and spectral fitting of ACIS X-ray sources via calls to CIAO tools and to XSPEC. AE has been available to the Chandra community since February 2003. It has been used extensively within the ACIS team, for example on the Chandra Deep Fields, the Galactic Center, and on many star formation regions including the Chandra Orion Ultradeep Project.

In 2004 and 2005 development of AE has continued at a steady pace to support evolution in CIAO and to extend AE's capabilities. AE now supports extraction and fitting of diffuse emission regions, generating appropriately weighted ARFs and RMFs. It provides smart masking of point sources, choosing masks matched to source brightness to avoid unnecessary loss of any surrounding diffuse signal. Nominal extractions have been more fully automated, and recipes for complex extractions (including stacking for faint or undetected sources as well as annular extractions for piled up sources) have been provided. Support for the C-statistic in XSPEC has been added. Source characterization now includes a Maximum Likelihood image reconstruction of the neighborhood around each point source, adaptively smoothed light curves, median energy timeseries, and statistical errors on source positions. AE helps the observer decide which proposed point sources to accept by computing the probability that each source is a random fluctuation in the local background.


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A Software Tool for Analyzing ACIS Calibration Data

Gordon Garmire (The Pennsylvania State Univ.)

A JAVA-based software tool is commercially available that can be used analyze ACIS calibration data. The tool can be used to compute the gain and energy resolution for each CCD over preassigned areas of the CCD. The tool is available from Signostics, Inc. P. O. Box 780, Brookline, MA 02446-0006 and is called CCT & CCTA Version 2.0. Results from this software will be presented.

An Improved HRC-I Degapping Correction

Michael Juda (CXC/SAO)

Event positions from the HRC are not telemetered to the ground rather, they must be reconstructed during ground processing using the telemetered data for each axis of: the number of the amplifie along the axis with the largest signal and the amplitude of the signal on that amplifier and the amplifiers on either side (the three-tap position algorithm). There is a loss of information in sampling the position this way that produces gaps in images where the event positions are calculated using the simplest centroiding algorithm: $X_{fine} = \frac{A_{i+1} - A_{i-1}}{A_{i-1} + A_i + A_{i+1}}$ These gaps are removed by applying additional corrections to the simple centroid. Recently the CXCDS changed the method for degapping the event positions from a fifth-order polynomial function of $X_{fine}$ to one based on a look-up table. This change was made to more easily be able to account for various non-ideal effects in the HRC electronics. The values in the look-up table can be populated using the polynomial functions however, improved degapping corrections can be determined in limited regions on the detector using observations of near-on-axis point sources. I will describe a method of determining degapping corrections by using the aspect solution to predict the source location on the detector surface and comparing this to the event position reconstructed with the simplest centroiding algorithm (RAW position). I will present an example of a HRC-I look-up table with improved degapping corrections over a limited region and demonstrate the improvement in the PSF of an on-axis source that results from its use.

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Recent ACIS CCD Irradiation Experiments

Beverly LaMarr, Marshall Bautz, Catherine Grant, Steve Kissel, Gregory Prigozhin (MIT), Steve Brown (GSFC)

We report results of recent ACIS CCD irradiation experiments aimed at understanding the effect of a possible future ACIS bakeout on detector performance. Six front-illuminated detectors were irradiated cold, and then subjected to simulated bakeouts. The CCDs were irradiated with protons ranging in energy from 100 keV to 400 keV and "baked out" at temperatures ranging from +0 C to +30C. After each irradiation and thermal cycle the CCDs were characterized at 5.9keV. We conclude that a future ACIS bakeout probably cause only a modest degradation in ACIS detector performance.

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Monitoring the Optical/UV Transmission of the HRC with Betelgeuse

Jennifer Posson-Brown, Vinay Kashyap (CXC/SAO)

We have carried out a comprehensive analysis of all Betelgeuse calibration observations obtained to date with the HRC. Betelgeuse is undetected in all of the individual observations as well as cumulatively. We find that the expected exposure time for detection is greater than 1 Ms for aimpoint observations for both HRC-I and HRC-S. We also find that the predicted count rate due to the UV/optical flux is sufficient to have already resulted in a detection for observations carried out over the thin filter regions at large off-axis angles of the HRC-S. The non-detections therefore suggest that the out-of-band response must be decreased, by a factor less than 0.3.

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The Chandra Bibliography Database

Arnold Rots, Sherry Winkelman, Sarah Blecksmith, Alaine Duffy, Melissa Cirtain (SAO)

The Chandra Data Archive (CDA) Operations team maintains a database of published articles related to the Chandra X-ray Observatory that we consider to be as nearly complete as practical. The records in the database are based on the holdings of the Astrophysics Data System (ADS). Where possible and applicable, articles are linked to specific observations. The database stores a variety of additional metadata on each publication, including the type of publication, whether or not refereed, publication date, association with particular spacecraft subsystems or software, a contents categorization, multi-wavelength information, and keywords associated with the article.

We will highlight five aspects of the database: - Its maintenance software - Access to Chandra data from the ADS - Access to ADS articles from the CDA - Integrated scientific searching of articles and observations through the database - Compilation of statistics

Since the beginning of 2005 the astronomical journals allow authors to insert direct links to archived observational data in manuscripts. As this feature gets more commonly used it will make maintenance of the bibliography database easier and it may allow limited inclusion of articles from astro-ph.

This work has been supported by NASA under contract NAS 8-03060 to the Smithsonian Astrophysical Observatory for operation of the Chandra X-ray Center.


An Archive of Chandra Observations of Regions of Star Formation (ANCHORS)

Bradley Spitzbart, Natalya Bizunok, Scott Wolk (Harvard-Smithsonian Center for Astrophysics)

ANCHORS is a web based archive of point sources observed during Chandra observations of regions of star formation. It is designed to aid both the X-ray astronomer with a desire to compare X-ray datasets and the star formation astronomer wishing to compare stars across the spectrum. Automated pipeline processing ensures consistent analysis techniques for direct comparisons among clusters and observing epochs. Through cycle 5 the database contains about 60 Chandra fields yielding 10,000+ sources. The data consists of X-ray source properties including position, net count rates, flux, lightcurves and spectral fits using Raymond-Smith thermal plasma models. Multi-wavelength images and data are cross-linked to other archives such as 2MASS, Spitzer, SIMBAD, and ADS. Results are presented on-line with sorting, searching, and download functions via a HTML/XML interface. Scientifically, the range of star-forming regions available in ANCHORS advances our understanding of the progression of luminosity, variability, and flaring for various-mass stars. Additionally, the archive provides calibration metrics for monitoring the spacecraft and instrument performance during Chandra's lifetime. This project is supported by Chandra archival grant AR5-6002A and NASA contract NAS8-39073.


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The HRC-I Gain Map

Charles Wilton, Jennifer Posson-Brown, Michael Juda, Vinay Kashyap (CXC/SAO)

We have derived a gain map for the HRC-I based on laboratory and flight data. We use lab flat-field data at six energies to obtain median values of the gain, and combine to construct an average gain uniformity map. This gain map is then modified to match the on-axis PHA profile of AR Lac, using a raster of off-axis AR Lac calibration observations carried out at current flight voltage settings. The final gain correction map has been released and will be available in the Chandra CALDB.

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