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Abstracts from the Chandra Calibration Workshop

Title: Overview of Chandra Optics
Authors: Diab Jerius (CXC/SAO)
Presenter: Diab Jerius
Presentation Type: Oral
Abstract: The Chandra X-Ray Observatory (CXO) mirrors (the High Resolution Mirror Assembly, or HRMA) were designed to produce images with better than one arc-second resolution, and to concentrate better than 85% of the energy at 0.277 keV within a 1 arcsec diameter. As good as the optics are, they have a complicated PSF which is a strong function of energy and source position. This presentation provides an overview of Chandra's optics, important characteristics of their performance, and the direction of the calibration effort.
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Title: Calibrating the PSF: Comparisons of Models to Data
Authors: Diab Jerius (CXC/SAO)
Presenter: Diab Jerius
Presentation Type: Oral
Abstract: Chandra's PSF is a complicated function of source position, energy, and the focal plane detector. Calibration of the PSF is usually done by parameterizing some characteristic of the PSF, such as its radial profile or encircled energy function. With Chandra, however, we have at our disposal a model, SAOsac, which has successfully predicted the optics' performance during ground calibration, and has proven effective in qualitatively describing the on-orbit performance. This presentation details results of an analysis which utilizes the PSF azimuthally averaged profile as well as it's encircled energy fractions to calibrate the model.
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Title: Wings of the Chandra PSF
Authors: Terry Gaetz (CXC/SAO)
Presenter: Terry Gaetz
Presentation Type: Oral
Abstract: The surface microroughness of the Chandra X-ray mirrors scatter incident X-rays. These scattered X-rays produce faint PSF wings extending to large angles. In order to improve the characterization of the PSF wings, a deep calibration observation of Her X-1 was performed. The galactic NH column is small in this direction, greatly reducing the possibility of contamination by an astrophysical dust X-ray scattering halo. I present the results of analyses of the Her X-1 data set, and the implications for the calibration of the wings.
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Title: Parameterization of Chandra's PSF
Authors: Diab Jerius (CXC/SAO)
Presenter: Diab Jerius
Presentation Type: Oral
Abstract: A parameterization of Chandra's PSF would be a useful tool for simple analysis of Chandra data. This presentation describes various approaches and their pitfalls and discusses parameterization of the on-axis PSF via encircled-energy fractions.
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Title: Chandra aspect performance
Authors: Tom Aldcroft (SAO), Rob Cameron (SAO)
Presenter Tom Aldcroft
Presentation Type: Oral
Abstract:I will present a summary of the performance of the Chandra aspect determination system, focusing on image reconstruction and absolute astrometry. Image reconstruction measures the effective blurring of the HRMA PSF due to aspect uncertainty, while absolute astrometry gives the accuracy of source X-ray coordinates determined by Chandra. I will show examples of how to search for any aspect-related image blurring in Chandra data and how to use the fix_offset tool to remove any aspect offsets in archival data.
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Title: The HRC Degapping Procedure
Authors: Almus Kenter (SAO)
Presenter Almus Kenter
Presentation Type: Oral
Abstract: The event postions for the HRC detectors must be corrected to take into account the fact that only a fraction of the charge from the MCPs is collected by the detector crossed grids. Not performing this correction causes small scale distortions on the scale of the amplifier read-outs and causes "gaps" in the reconstructed x-ray positions. A "de-gapping" algorithm for the HRC data has been developed using laboratory flat-field illumination data and a statistical technique employing transformation of probability distributions.
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Title: Imaging characteristics affecting the LETGS
Authors: Vinay Kashyap (CXC/SAO), Jeremy Drake (CXC/SAO), Brad Wargelin (CXC/SAO), Deron Pease (CXC/SAO), Pete Ratzlaff (CXC/SAO)
Presenter Vinay Kashyap
Presentation Type: Oral
Abstract: We discuss the imaging characteristics that affect the response of the LETGS, including the line response function, cross-dispersion, extraction efficiencies, degapping, etc.
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Title: Non-linearities in the HRC-S detector
Authors: Rob van der Meer (SRON, the Netherlands), Jelle Kaastra (SRON, the Netherlands), Mariano Mendez (SRON, the Netherlands)
Presenter Rob van der Meer
Presentation Type: Oral
Abstract: We used LETG/HRC-S Capella observations to measure non-linearities in the spa tial coordinates of the HRC-S detector. In the Capella spectrum some of the strong emission lines had a non-symmetric shape and were not exactly at the predicted position. We use the satellite´s dithering pattern to map strong nearly monochromatic emission lines on different parts of the detector. The accuracy of the line centroids before the correction was about 10 mA. With the correction the accuracy of the wavelengthscale is about 2 mA.
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Title: HRC-I and HRMA Calibration Using RXJ1856.5-3754
Authors: Brad Wargelin (SAO/CXC), Jennifer Posson-Brown (SAO/CXC), Michael Juda (SAO/CXC), Diab Jerius (SAO/CXC), Terry Gaetz (SAO/CXC), Kester Allen (SAO/CXC)
Presenter Brad Wargelin
Presentation Type: Oral
Abstract: Simultaneously with the recent ACIS undercover background measurements, the HRC-I was run in Next-In-Line mode at an off-axis angle of 25.62 arcmin to observe the isolated neutron star, RXJ1856.5-3754. This source has a blackbody spectrum, previously characterized using the HRC-S, peaking around the C-K edge, an energy range which is not well calibrated for the HRC-I. Together with a short on-axis observation, the NIL data are being used to calibrate the absolute HRC-I on-center QE, QE uniformity, vignetting function, and off-axis PSF.
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Title: Low energy Uniformity in the Quantum Efficiency of the HRC-I
Authors: R. Hank Donnelly (CXC/SAO), J.P. Brown (CXC/SAO)
Presenter R. Hank Donnelly
Presentation Type: Oral
Abstract: We report on the characterization of the uniformity of the quantum efficiency at low energies (kT < 0.5 keV) for the HRC-I. Using observations of the bright point source HZ43 at several off axis angles along with an observation of the Vela supernova remnant, we are developing an model of the instrument performance in this spectral regime.
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Title: HRC-S event double-counting and deadtime correction
Authors: Michael Juda (SAO/CXC), Jack Gomes (SAO/HRC), Almus Kenter (SAO/HRC), Martin Zombeck (SAO/HRC)
Presenter Michael Juda
Presentation Type: Oral
Abstract: The deadtime correction calculation for the HRC uses data from rate scalars that count all MCP triggers and triggers that pass the on-board validity criteria. However, due to differences in pulse shapes from those on the HRC-I, large events on the HRC-S are counted twice by the scalars. This double-counting leads to an incorrect deadtime calculation, particularly for time intervals that suffer from telemetry saturation. We present a statistical correction for the rates and deadtime calculation based on the observed events.
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Title: The UV/Visible Light Sensitivity of the HRC
Authors: Martin Zombeck (CfA), Bradford Wargelin (CfA)
Presenter Martin Zombeck
Presentation Type: Oral
Abstract: Effective area curves for the UV/Visible response of HRC-I and -S will be presented along with comparisons of predicted and observed count rates for Vega and Betelgeuse. Models for the prediction of count rates for a star whose effective temperature is known will be presented also.
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Title: Characteristics of the HRC Background
Authors: Michael Juda (CXC/SAO)
Presenter Michael Juda
Presentation Type: Oral
Abstract: The observed spatial and temporal characteristics of the backgrounds in the HRC-I and HRC-S will be reviewed.
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Title: The Decrease in the ACIS Low-energy Sensitivity
Authors: Paul Plucinsky (CXC/SAO), Norbert Schulz (CXC/MIT), Herman Marshall (CXC/MIT), Catherine Grant (ACIS/MIT), George Chartas (ACIS/PSU), Divas Sanwal (ACIS/PSU), Marcus Teter (ACIS/PSU), Alexey Vikhlinin (CXC/SAO), Richard Edgar (CXC/SAO), Shanil Virani (CXC/SAO), Joseph DePasquale (CXC/SAO), Michael Raley (CXC/SAO)
Presenter Paul Plucinsky
Presentation Type: Oral
Abstract: The detection efficiency of the ACIS instrument has been declining throughout the mission, presumably due to a layer of contamination building up on the filter and/or CCDs. We will review the evidence for the decrease in detection efficiency and describe its impact on spectral fitting of strophysical sources. We will present results of spectral fits with and without a time-dependent correction for the sensitivity decrease.
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Title: Interpreting ACIS Observations in Light of Recent Calibration Issues
Authors: George Chartas (Penn State)
Presenter George Chartas
Presentation Type: Oral
Abstract: We have developed the tool ACISABS to correct for the ACIS time dependent absorption due to molecular contamination. We plan to briefly describe the ACIS qe correction tool and suggest refinements of the tool based on future calibration data. For the purposes of bare ACIS spectral analysis ACISABS appears to produce reasonable results based on fits to several test-sources. We plan to present cases where we have applied the tool to several ACIS observations and show how the non-inclusion of this correction can lead to erroneous results. An instrumental effect that occasionally is neglected in the analysis of ACIS observations is related to the distortion of ACIS spectra due to the selected spectral extraction region. We present the simple tool XPSF that corrects the arf file for the selected aperture at a given source location. We finally present an application of XPSF to correct for piled-up spectra.
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Title: Verifying the ACIS QE Uniformity using the HETGS
Authors: Herman Marshall (MIT)
Presenter Herman Marshall
Presentation Type: Oral
Abstract: Using observations of 3C 273 at several SIM Z offsets, the nonuniformity of the ACIS QE can be examined. Three of the five data sets have been obtained already and the preliminary results from the analysis of these data will be presented.
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Title: ACIS background
Authors: Maxim Markevitch (SAO)
Presenter Maxim Markevitch
Presentation Type: Oral
Abstract: I will review the ACIS background calibration, including the recent ACIS-stowed observations, the dark Moon data, the quiescent blank-sky datasets for different time periods, and some new methods of the background flare correction.
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Title: ACIS Optical Sensitivity
Authors: Scott Wolk (CfA), Peter Ford (MIT)
Presenter Scott Wolk
Presentation Type: Oral
Abstract: The optical sensivity of ACIS is somewhat higher than pre-orbit expectations. There are several methods available now to mitigate the problem and ACIS has sucessfully observed Venus, Mars and has approved observations of Jupiter and Saturn scheduled. I discuss the impact of optical contamination and methods available to ameliorate the problem. Finally, I will highlight calibration and science results on bright planetary targets.
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Title: Evolution of ACIS charge transfer inefficiency
Authors: Catherine Grant MIT/CSR , ACIS IPI team
Presenter Catherine Grant
Presentation Type: Oral
Abstract: Over the lifetime of Chandra, the performance characteristics of ACIS will continue to evolve. I will present the history of ACIS CTI and gain to the present time and discuss expectations for the future. I will also describe, in general terms, how this evolution affects science data and a method for testing the validity of calibration products for specific time periods.
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Title: Including CTI Time Dependence in the PSU CTI Corrector
Authors: Leisa Townsley (Penn State University), Patrick Broos (Penn State University), Catherine Grant (MIT)
Presenter Leisa Townsley
Presentation Type: Oral
Abstract: Changes in CTI with time have been measured and quantified by C. Grant. A model for these changes (for each CCD) was incorporated into the PSU CTI corrector in May 2002;; this model is described. We demonstrate the performance of the PSU CTI corrector with and without the time dependence and suggest that this enhancement could be used to improve our current CTI model by including a larger database of calibration observations and by performing iterative corrections to the calibration data.
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Title: ACIS CC mode calibration
Authors: Divas Sanwal (PSU), ACIS IPI Team
Presenter Divas Sanwal
Presentation Type: Oral
Abstract: Continuous Clocking (CC) mode of the ACIS instrument provides both spectral and timing capabilities, but this mode is not well calibrated. Currently, the calibration products for the Timed Exposure (TE) mode are used for the spectral analysis of the CC mode data. First calibration observations in the CC mode of the onboard External Cal source were performed this summer. Using the calibration observation data in CC mode available by the time of this workshop, we will present the comparison of the CC and TE observations. This will test if using TE mode calibration products for the spectral analysis of the CC data is appropriate or not.
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Title: ACIS Response
Authors: Richard Edgar (SAO)
Presenter Richard Edgar
Presentation Type: Oral
Abstract: We report on the generation and testing of new Fits Encoded Function files (FEFs) which embody the model of the spectral response of the ACIS front-illuminated (FI) chips I0123 and S2, as modified by the CXC Charge Transfer Inefficiency (CTI) corretion software. These FEFs, from which users can construct Response Matrix Files (RMFs) using CXC tools, should be released at approximately the time of the workshop. They will allow spectral fitting using the improved resolution provided by CTI correction on the FI devices. Sample fits of astrophysical sources using the new response products will be presented.
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Title: Performance Tests and Verification of current ACIS FEFs
Authors: Norbert S. Schulz (MIT)
Presenter Norbert S. Schulz
Presentation Type: Oral
Abstract: The external calibration source is an integral part of the ACIS in-flight response calibration. Before released to the public the energy scale and line response of each tile in each node of every CCD is tested against the standard of the external calibration line sources at Al-K, Ti-K, and Mn-K for energies between 1.5 and 6 keV. For low energies we apply the LETG to disperse the X-ray continuum of a bright celestrial point source across various CCDs of the ACIS-I and ACIS-S instruments. In the case of S3 we are also using these measurements to correct for low energy gain shifts across the entire device. We test the low energy redistribution against the current model.
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Title: Future ACIS Calibration work
Authors: Dan Schwartz (Harvard/Smithsonian), and the ad hoc ACIS Modeling and An CXC/MIT/PSU/MSFC
Presenter Dan Schwartz
Presentation Type: Oral
Abstract: Over the past year an ad hoc ACIS Modeling and Analysis group has made tangible progress, releasing a new model of the S3 spectral response at -120 degrees, and developing cti-corrected response models for the ACIS-I array and S2. In this talk I list some of the "whats" of future calibration work: Investigation of quantum efficiency, including reconciliation of the BI and FI chips and understanding the time dependent low energy changes. Producing time dependent CTI-corrected FI FEF and gain, over appropriate time intervals which we need to determine. Producing CTI-corrected FI FEF for various conditions of frame time and total counting rate. The last series of products is needed in principle because the effects of CTI depend sensitively on the amount of charge available to fill traps downstream of the X-ray event of interest. We also need products for Continuous Clocking mode, and for some of the warmer temperatures at which ACIS operated early in the mission. We look to the User Community to help define the relative priorities for these investigations.
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Title: Exploring the limits of the ACIS Pile-up Model
Authors: John Davis (MIT/CXC)
Presenter John Davis
Presentation Type: Oral
Abstract: Last year I proposed a statistical model of photon pile-up in CCDs for the analysis of ACIS imaging observations of bright sources. The model has since been implemented in the ISIS, SHERPA, and XSPEC software packages, and as such, it is readily available to the X-Ray astronomical community at large. More recently, the model has been extended to to treat pile-up in the dispersed spectrum of HETG observations. In an effort to better characterize the range of applicability of the model, and to explore its limitations, I will show some examples of its application to a wide variety of Chandra observations that suffer from varying degrees of pile-up. Both imaging and grating observations will be presented.
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Title: LETG Higher Order Diffraction Efficiencies
Authors: Brad Wargelin (SAO/CXC), Pete Ratzlaff (SAO/CXC)
Presenter Brad Wargelin
Presentation Type: Oral
Abstract: First and 0th order LETG efficiencies are well calibrated, but those for higher orders may need to be adjusted. We present results from analyses of XRCF data and an LETG/ACIS-S observation of the very bright x-ray nova, XTE J1118.
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Title: Comparison of the gratings when measuring the NeIX triplet at 13.5 A
Authors: Jan-Uwe Ness (Hamburger Sternwarte), Nancy Brickhouse (CfA), Jeremy Drake (CfA), David Huenemoerder (MIT)
Presenter Jan-Uwe Ness
Presentation Type: Oral
Abstract: The grating instruments on board Chandra cover a variety of chances and limitations. While the LETGS offers the largest wavelength range with high sensitivity the MEG and the HEG have a much higher spectral resolution. A very popular method to analyze the grating spectra is the He-like triplets because they are density sensitive and a large temperature range is covered with different ions ranging from C V ($\sim1$\,MK) up to Si XIII ($\sim 15$\,MK). However, only the LETGS wavelength range covers all these triplets simultaneously, while with the MEG the C V and the N VI triplets are not measurable and the HEG can only measure Si XIII, Mg XI, and Ne IX. The Ne IX triplet can be measured with all instrument, but with different success. The triplet line are in principle resolved by all grating, but severe blending with Fe XIX line can hamper the analysis in the hotter plasmas, e.g., active stars or flares. In those cases highest spectral resolution is highly desirable, and the LETGS is not sufficient to resolve all blending lines. The most popular X-ray calibration target is Capella and it has been observed with all gratings with significant exposure times. We gathered together all available data of the HEG and MEG (155 ksec), the LETGS (219 ksec) for comparative analysis of the Ne IX triplet. 18 emission lines can be identified in the region around 13.5 A with the HEG. Good agreement of these lines with predictions from a theoretical model constructed from the APEC line database using an emission measure distribution derived from Fe IX to Fe XXIV lines can be seen. These 18 emission lines cannot be identified in the LETGS spectrum, but we show that these spectra are consistent with the wavelengths and fluxes measured with the HEG.
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Title: Updates to the HETGS Effective Area
Authors: Herman Marshall (MIT)
Presenter Herman Marshall
Presentation Type: Oral
Abstract: The effective area of the HETGS will be updated based on analysis of several in-flight calibration sources such as 3C 273 and PKS 2155-304. Modifications that are being prepared for release affect the ACIS QE below 1 keV, the grating efficiencies between 1 and 2 keV and the Ir M edge just above 2.1 keV. In addition, the ACIS contamination affects data below 1 keV but will be presented in a separate talk.
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Title: Grating Spectral Order Sorting with the ACIS CCDs
Authors: David Huenemoerder (MIT)
Presenter David Huenemoerder
Presentation Type: Oral
Abstract: To sort overlapping spectral orders imaged from the HETG or LETG instruments onto the ACIS-S detector array, we use the CCD energy redistribution response as a function of position and energy. During analysis, we use the same response to calibrate the effective area fraction implicit in order-sorting. We attempt to maintain a high and nearly constant enclosed energy fraction, but CCD gain and response variations make this difficult. The order-sorting has not been highly visible to users. I will show some examples of good and bad order-sorting, discuss options for inspection and reprocessing before analysis, and talk about plans for construction of the next generation tables, given the new formalism for defining the ACIS redistribution which is currently being implemented.
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Title: On the use of HETGS higher order spectra for science analysis
Authors: Norbert S. Schulz (MIT)
Presenter Norbert S. Schulz
Presentation Type: Oral
Abstract: Orders higher than one in the HETGS are usually dismissed in most science analyses as they offer only a fraction of the first order bandpass and possess an order of magnitude lower efficencies. Some sources, usually X-ray binaries, however are bright enough to produce significant higher order spectra. I will review the current status of their calibration. For various examples I will demonstrate how these spectra can aid the science analysis in the case that first order spectra are affected by pileup, but also show the benefits of higher spectral resolution. I will also show how we specifically use the HETGS higher orders to observe Sco X-1.
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Title: Absolute Time Calibration
Authors: Arnold Rots (SAO/CXC)
Presenter Arnold Rots
Presentation Type: Oral
Abstract: The two main components in assigning an absolute time to an event are determining the local time on board of the spacecraft and transforming this local time to a fixed time scale, such as TDB. Contributing to the errors in the former are errors in the orbit ephemeris, the various signal delays, and the calibration measurement itself. Contributing to the latter are the orbit ephemeris and the solar system ephemeris used for the transformation. The quoted accuracy of the Chandra clock is 0.1 ms;; however, we should be able to do better: delays can be measured more accurately and the accuracy of orbit ephemeris is better than 30 km, while the clock bits in the HRC events allow a relative accuracy of 0.016 ms. The ultimate test is to conduct a series of pulsar observations, coordinated with RXTE;; that work is still incomplete and somewhat inconclusive. Up till this time there are still discrepancies of a little more than 0.1 ms in the system.
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Title: Computation of Times of Arrival for CC Mode Events
Authors: Glenn Allen (MIT), Peter Ford (MIT), Jim Francis (MIT), Kenny Glotfelty (CfA), David Huenemoerder (MIT), Joel Kastner (RIT), Jonathan McDowell (CfA), Herman Marshall (MIT), Arnold Rots (CfA), Divas Sanwal (PSU), Allyn Tennant (NASA MSFC)
Presenter Glenn Allen
Presentation Type: Oral
Abstract: We describe how the times of arrival of events are computed in continuous clocking mode observations, show how to use the tool acis_process_events to (re)perform the computation, and compare the results obtained using acis_process_events with results obtained using "independent" algorithms to demonstrate the accuracy of the computations.
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Title: Spacecarft Stability
Authors: Scott Wolk (CfA)
Presenter Scott Wolk
Presentation Type: Oral
Abstract: The Monitoring and Trends program is part of the Science Operations team at the CXC. The goal of the MTA program is to monitor and trend all spacecraft and science data in an effort to anticipate trouble and take action before science has been impacted. The key result is that, with a couple of notable exceptions, the spacecraft has been remarkably stable. I examine what could change in the next few years and the impact observation design and on data analysis.
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Title: Overview of Chandra Calibration
Authors: Laurence David (SAO/CXC)
Presenter Laurence David
Presentation Type: Oral
Abstract: I will review the main Chandra calibration issues that have been addressed over the past year.These investigations have produced updates to some calibration products and new software models. Each of the revised products will be discussed, briefly highlighting the primary improvements. I will also discuss the main areas of concentration at the present time, and the remaining uncertainties in Chandra calibration.
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Title: Effects of HRC status bit filtering
Authors: Charles Wilton (CXC/SAO), Michael Juda (CXC/SAO)
Presenter Charles Wilton
Presentation Type: Poster
Abstract: The effects of HRC status bit filtering on the flight and laboratory calibration data are presented. The status bit filters serve a valuable function in that they remove events that are likely not the result of x-rays or are misplaced. However, filtering of events of HRC-I laboratory flat field data shows pronounced position- and energy-dependent loss of events. The choice of status bits can profoundly alter the apparent response of the HRC detectors and should be understood by calibration staff and users of the HRC.
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Title: A New Flight Model of the HRC-I MCP Quantum Efficiency
Authors: Jennifer Posson-Brown (CXC/SAO), R. Hank Donnelly (CXC/SAO), K. Tabetha Hole (University of Wisconsin)
Presenter Jennifer Posson-Brown
Presentation Type: Poster
Abstract: We present a new flight model of the HRC-I MCP quantum efficiency. Using several astrophysical sources, we have updated the original flight model to reflect the true broadband performance of the detector. In addition, we have adapted the relative response of the HRC-S at low energies (kT < 626 eV) in order to improve the detailed relative response which was previously poorly known. The new model more accurately reflects our knowledge of the in-flight performance of the HRC-I, and has significantly smaller uncertainties at lower energies relative to the original flight model.
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Title: ACIS Low Energy Response Results for 3 Pulsars
Authors: Marcus A. Teter (Penn State), et al.
Presenter Marcus A. Teter
Presentation Type: Poster
Abstract: We present the results of the application of the ACISABS tool to the data on three pulsars observed with Chandra to demonstrate the current status of the ACIS low energy response. The ACIS spectra for each source were compared to LETGS and archival ROSAT PSPC spectra to determine the quality of the ACIS fit both before and after using the ACISABS tool. We also summarize the physical model spectral parameters and their errors in both cases.
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Title: The Chandra Off-Axis Point Spread Function
Authors: Christopher Allen (CXC), Diab Jerius (CXC)
Presenter Christopher Allen
Presentation Type: Poster
Abstract: We present metrics for the Chandra off-axis PSF, generated using the official Chandra mirror model, SAOsac. We describe the PSF with elliptical isophotes fitted in IRAF containing particular fractions of the total beam energy. The metrics characterize the PSF in terms of the ellipses´ semi-major axes and rotation angle, and cover a range of monochromatic energies between 0.277 keV and 8 keV and a spatial grid of off-axis positions which covers the focal surface. We present the results for the HRC-I detector.
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Title: Modelling Chandra: Positional accuracy of Mirror and Detector Models
Authors: Eli Beckerman (SAO/CXC)
Presenter Eli Beckerman
Presentation Type: Poster
Abstract: Chandra users will soon have two ways of modelling sources observed with Chandra -- MARX, and a new tool, ChaRT. ChaRT is a web front end to the official Chandra mirror model, SAOsac, which until now was not available for the end user. MARX also provides detector models. The CIAO tool psf_project_ray, which is designed to be used with the events generated by SAOsac, provides a model of the detector geometries. We present the first in a series of studies comparing the accuracy of the models. We focus here on the positional accuracy, that is, can the models correctly predict where a source will appear on a detector. We compare events generated by SAOsac and detected by MARX, psf_project_ray, and a third, engineering model, deticpt, as well as events generated by MARX and detected by MARX. We present results for various off-axis pointings of AR Lac and LMC-X1 on all of Chandra´s detectors.
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Title: CTI Correction on the Backside-illuminated CCD S3: How and Why
Authors: Leisa Townsley (PSU), Patrick Broos (PSU), John Nousek (PSU), Gordon Garmire (PSU)
Presenter Leisa Townsley
Presentation Type: Poster
Abstract: The PSU CTI corrector was first developed to account for the CTI in the backside-illuminated (BI) ACIS CCDs. This CTI is modest compared to the radiation-induced CTI present in the frontside-illuminated (FI) chips. It comes about as part of the manufacturing process, so it was known to exist well before launch. Thus we developed a preliminary phenomenological model for this BI CTI, including both parallel and serial components, that was to form the basis for the FI CTI corrector that became necessary after launch. Here we review the details of the BI corrector and its RMF and give astrophysical examples showing why correcting BI data is worthwhile.
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Title: Chandra Grating LSF for Dummies
Authors: Kazunori Ishibashi (MIT/CSR)
Presenter Kazunori Ishibashi
Presentation Type: Poster
Abstract: A crush course on Chandra grating LSFPARMS will be given to users. The goals will be to inform potential users on the validity of the new LSFPARMS product and its limitations. The presentation will focus on examples using ACIS-S/HETG.
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Title: In-flight calibration of the C edge fine-structure in the HRC UV/ion shield transmission models
Authors: Deron Pease (CXC/SAO), Jeremy Drake (CXC/SAO), Vinay Kashyap (CXC/SAO), Herman Marshall (MIT)
Presenter Deron Pease
Presentation Type: Poster
Abstract: We present details on the in-flight calibration of the HRC UV/ion shield transmission efficiency models. The broad shapes of the UV/ion shield models were derived from pre-flight measurements made at the HRC X-ray Test Facility at SAO. Further C,O,N,Al absorption edge structure measurements were made at the BESSY 1 synchrotron light source. However, during in-flight LETG/HRC-S calibration it became apparent that the HRC-S UVIS absorption fine structure was incompletely modeled, particularly the strong C-K edge. From in-flight observations of the AGN PKS 2155-304 and 3C 273, and the compact object RX J1856.5-3754, we have improved calibration of the HRC UV/ion shield transmission models, in 2 significant updates since launch.
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Title: In-flight effective area calibration of the Chandra low energy transmission grating spectrometer
Authors: Deron Pease (CXC/SAO), Jeremy Drake (CXC/SAO), Vinay Kashyap (CXC/SAO), Herman Marshall (MIT), Erica L. Raffauf(CXC/SAO), Peter W. Ratzlaff(CXC/SAO), Bradford J. Wargelin(CXC/SAO)
Presenter Deron Pease
Presentation Type: Poster
Abstract: We present the in-flight effective area calibration of the Low Energy Transmission Grating Spectrometer (LETGS), which comprises the High Resolution Camera Spectroscopic readout (HRC-S) and the Low Energy Transmission Grating (LETG) aboard the Chandra X-ray Observatory. Previous studies of the LETGS effective area calibration have focused on specific energy regimes: 1)the low-energy calibration for which we compared observations of Sirius B and HZ 43 with pure hydrogen non-LTE white dwarf emission models; and 2)the mid-energy calibration for which we compared observations of the active galactic nuclei PKS 2155-304 and 3C 273 with simple power-law models of their seemingly featureless continua. The residuals of the model comparisons were taken to be true residuals in the HRC-S quantum efficiency (QE) model. Additional in-flight observations of celestial sources with well-understood X-ray spectra have served to verify and fine-tune the calibration. Thus, from these studies we have derived corrections to the HRC-S QE to match the predicted and observed spectra over the full practical energy range of the LETGS. Furthermore, from pre-flight laboratory flatfield data we have constructed an HRC-S quantum efficiency uniformity (QEU) model. Application of the QEU to our semi-empirical in-flight HRC-S QE has resulted in an improved HRC-S on-axis QE. Implementation of the HRC-S QEU with the on-axis QE now allows for the computation of effective area for any reasonable Chandra LETGS pointing.
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Title: After-glow events not removed by CXC software
Authors: Gordon Garmire (Penn State University), Audrey Garmire (Penn State University)
Presenter Gordon Garmire
Presentation Type: Poster
Abstract: After-glow pusles have been detected in event2 files, where the events are separated from the intial event by one or several exposures. The frequency is not high, several percent, and is only important for faint sources, ones consisting of only a few events. The aftergow events are generally smaller in amplitude than the inital event, and may include one or two events.
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