Mitigating Charge Transfer Inefficiency in the [ITAL]Chandra X-Ray Observatory[/ITAL] Advanced CCD Imaging Spectrometer

Townsley, Leisa K.; Broos, P. S.; Garmire, G. P.; Nousek, J. A.

doi:10.1086/312672

Cited by 161 publications

(152 citation statements)

References 8 publications

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“…In what follows, we use only the S3 chip data. The data were processed following the CIAO data reduction threads, including a correction for charge transfer inefficiency (CTI; Townsley et al 2000). In addition, we used 38 ks of archival ACIS observations of M87 taken on 2000 July 29 (principal investigator: A. S. Wilson).…”

Section: Observations and Data Reductionsmentioning

confidence: 99%

The ACS Virgo Cluster Survey. III.ChandraandHubble Space TelescopeObservations of Low‐Mass X‐Ray Binaries and Globular Clusters in M87

Jordán

Côté

Ferrarese

et al. 2004

ApJ

131

150

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The ACIS instrument on board the Chandra X-Ray Observatory has been used to carry out the first systematic study of low-mass X-ray binaries ( LMXBs) in M87, the giant elliptical galaxy near the dynamical center of the Virgo Cluster. These images-with a total exposure time of 154 ks-are the deepest X-ray observations yet obtained of M87. We identify 174 X-ray point sources, of which $150 are likely LMXBs. This LMXB catalog is combined with deep F475W and F850LP images taken with ACS on the Hubble Space Telescope (HST ) (as part of the ACS Virgo Cluster Survey) to examine the connection between LMXBs and globular clusters in M87. Of the 1688 globular clusters in our catalog, f X ¼ 3:6% AE 0:5% contain an LMXB. Dividing the globular cluster sample by metallicity, we find that the metal-rich clusters are 3 AE 1 times more likely to harbor an LMXB than their metalpoor counterparts. In agreement with previous findings for other galaxies based on smaller LMXB samples, we find the efficiency of LMXB formation to scale with both cluster metallicity Z and luminosity, in the sense that brighter, more metal-rich clusters are more likely to contain an LMXB. For the first time, however, we are able to demonstrate that the probability p X that a given cluster will contain an LMXB depends sensitively on the dynamical properties of the host cluster. Specifically, we use the HST images to measure the half-light radius, concentration index, and central density 0 for each globular and define a parameter À, which is related to the tidal capture and binary-neutron star exchange rate. Our preferred form for p X is then p X / À À0:42AE0:11 0 (Z=Z ) 0:33AE0:1 . We argue that if the form of p X is determined by dynamical processes, then the observed metallicity dependence is a consequence of an increased number of neutron stars per unit mass in metal-rich globular clusters. Finally, we present a critical examination of the LMXB luminosity function in M87 and reexamine the published LMXB luminosity functions for M49 and NGC 4697. We find no compelling evidence for a break in the luminosity distribution of resolved X-ray point sources in any of these galaxies. Instead, the LMXB luminosity function in all three galaxies is well described by a power law with an upper cutoff at L X $10 39 ergs s À1 .

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Section: Observations and Data Reductionsmentioning

confidence: 99%

The ACS Virgo Cluster Survey. III.ChandraandHubble Space TelescopeObservations of Low‐Mass X‐Ray Binaries and Globular Clusters in M87

Jordán

Côté

Ferrarese

et al. 2004

ApJ

131

150

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“…The satellite and instrument are described by Weisskopf, O'Dell, &van Speybroeck (1996) andG. Garmire, J. Nousek, &M.…”

Section: Data Acquisition and Reductionmentioning

confidence: 99%

AChandraStudy of Sagittarius A East: A Supernova Remnant Regulating the Activity of Our Galactic Center?

Maeda

Baganoff

Feigelson

et al. 2002

ApJ

Self Cite

191

222

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We report on the X-ray emission from the shell-like, nonthermal radio source Sgr A East (SNR 000.0+00.0), located in the inner few parsecs of the Galaxy based on observations made with the ACIS detector on board the Chandra X-Ray Observatory. This is the first time Sgr A East has been clearly resolved from other complex structures in the region. The X-ray-emitting region is concentrated within the central '2 pc of the larger radio shell. The spectrum shows strong K lines from highly ionized ions of S, Ar, Ca, and Fe. A simple isothermal plasma model gives electron temperature $2 keV, absorption column $1 Â 10 23 H cm À2 , luminosity $8 Â 10 34 ergs s À1 in the 2-10 keV band, and gas mass $2 1=2 M with a filling factor . The plasma appears to be rich in heavy elements, overabundant by roughly a factor of 4 with respect to solar abundances, and shows a spatial gradient of elemental abundance; the spatial distribution of iron is more compact than that of the lighter elements. The gas mass and elemental abundance of the X-ray emission support the long-standing hypothesis that Sgr A East is a supernova remnant (SNR), perhaps produced by the Type II supernova explosion of a massive star with a main-sequence mass of 13-20 M . The combination of the radio and X-ray morphologies classifies Sgr A East as a new metal-rich '' mixed morphology '' (MM) SNR. The size of the Sgr A East radio shell is the smallest of the known MM SNRs, which strongly suggests that the ejecta have expanded into a very dense interstellar medium. The ejecta-dominated chemical compositions of the plasma indicate that the ambient materials should be highly homogeneous. We thus evaluate a simplified dynamical evolution model where an SNR was formed about 10,000 yr ago and expanded into an ambient medium with a homogeneous density of 10 3 cm À3 . The model roughly reproduces most of the observed properties in the X-ray and radio wavelengths. A comparison with the radio observations requires the dense ambient medium to be ionized, but a luminous X-ray irradiator with an expected X-ray luminosity of $10 40 ergs s À1 is not currently present. The presence of the ionized gas may be explained if the massive black hole (MBH) associated with the compact, nonthermal radio source Sgr A* was bright in X-rays about 300 yr ago but is presently dim. It is possible that the dust/molecular ridge compressed by the forward shock of Sgr A East hit Sgr A* in the past, and the passage of the ridge may have supplied material to accrete onto the black hole in the past and may have removed material from the black hole vicinity, leading to its present quiescent state. This may be a specific example of the intimate relationship between an SNR and MBH accretion activity in galactic nuclei.

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“…As part of a monitoring program of SN 1987A, we have performed a total of four observations with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-ray Observatory (Weisskopf et al 1996(Weisskopf et al ) between 1999(Weisskopf et al and 2001 (Table 1) Over the past two years, the data reduction techniques developed at Penn State have expanded to include new methods for correcting the spatial and spectral degradation of the ACIS data caused by the radiation damage, known as Charge Transfer Inefficiency (CTI) (Townsley et al 2000;Townsley et al 2001a), and the use of charge spreading to obtain angular resolution at the sub-pixel level . The expected effects of the CTI correction include an increase of the number of detected events and improved event energies and the energy resolution (Townsley et al 2000;Townsley et al 2001a).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…The expected effects of the CTI correction include an increase of the number of detected events and improved event energies and the energy resolution (Townsley et al 2000;Townsley et al 2001a). By applying the "sub-pixel resolution" method, we expect the angular resolution to improve by ∼10% .…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Monitoring the Evolution of the X‐Ray Remnant of SN 1987A

Park

Burrows

Garmire

et al. 2002

ApJ

127

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We report on the results of our monitoring program of the remnant of SN 1987A with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-ray Observatory. Two new observations have been performed in AO2, bringing the total to four monitoring observations over the past two years. Over this time period, new techniques for correction of "Charge Transfer Inefficiency (CTI)" and for use of charge spreading to provide angular resolution somewhat better than the pixel size of the CCD detector have become available at Penn State. We have processed all four observations using sub-pixel resolution to obtain the highest possible angular resolution, and using our CTI correction software to provide more reliable spectral analysis and flux estimations.The high angular resolution images indicate that the X-ray bright knots are convincingly correlated with the optical spots, primarily at ∼ <1 keV, while higher energy photons are very well correlated with radio images. Our data also provide marginal evidence for radial expansion of the X-ray remnant at a rate of 5200 ± 2100 km s −1 . The X-ray flux appears to linearly increase by ∼60% over the 18 month period of these observations. The spectrum is dominated by broad complexes of atomic emission lines and can be fit with a simple model of a planeparallel shock with electron temperatures of kT ∼ 2 − 4 keV and a postshock electron density of n e ∼ 210 − 420 cm −3 . The implied 0.5 − 10 keV band luminosity in 2001 April is ∼1.3 × 10 35 ergs s −1 ; as of that date, we still observe no direct evidence for the central point source, with an upper limit on the observed luminosity of L X ∼ 5.5 × 10 33 ergs s −1 in the 2 − 10 keV band.

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Mitigating Charge Transfer Inefficiency in the [ITAL]Chandra X-Ray Observatory[/ITAL] Advanced CCD Imaging Spectrometer

Cited by 161 publications

References 8 publications

The ACS Virgo Cluster Survey. III.ChandraandHubble Space TelescopeObservations of Low‐Mass X‐Ray Binaries and Globular Clusters in M87

The ACS Virgo Cluster Survey. III.ChandraandHubble Space TelescopeObservations of Low‐Mass X‐Ray Binaries and Globular Clusters in M87

AChandraStudy of Sagittarius A East: A Supernova Remnant Regulating the Activity of Our Galactic Center?

Monitoring the Evolution of the X‐Ray Remnant of SN 1987A

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