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High-mass Star Formation Regions
I am leading the analysis of Gordon Garmire's ACIS GTO observations
of 30 Doradus, M17, and W51. I am also involved in X-ray studies
of the Rosette Nebula and Rosette Molecular Cloud,
the Orion Nebula Cluster, and NGC 1333.
30 Doradus ACIS data (smoothed using the CIAO tool "csmooth"):
Chandra/ACIS
Spectra of the 30 Doradus Star Forming Region
This is a poster paper from the January 2001 AAS meeting in San Diego.
It reviews some of our preliminary spectral analysis of the ACIS
GTO observation of 30 Doradus and updates our work on CTI and response
matrices for ACIS front-illuminated CCDs.
Chandra/ACIS
Observations of 30 Doradus
This is a poster paper from the January 2000 AAS meeting in Atlanta.
It shows some of the early images of the ACIS data on 30 Doradus and
outlines our early attempts to correct CTI on ACIS front-illuminated
CCDs.
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The PSU ACIS CCD Simulator, developed by Patrick Broos and Leisa Townsley
and written in IDL, is available from our Simulator
Webpage.
Charge Transfer Inefficiency
The back-illuminated (BI) chips in ACIS (S1 and S3) have always exhibited
marked charge transfer inefficiency (CTI) due to their manufacturing process.
We have been working on amelioration techniques for this kind of CTI
for several years. At the beginning of on-orbit operations the front-illuminated
(FI)
ACIS chips were damaged by radiation, so now they also exhibit CTI,
to a more severe degree than the BI chips.
In an attempt to understand the mechanism of the radiation damage, a
subset of the PSU ACIS team (the "Gold-L Team") tracked the CTI through
the
early part of the Orbital Activation Phase by following the behavior
of the Au L instrumental emission line present in celestial observations.
I produced
a report
of our studies.
Patrick Broos and I subsequently developed a technique to recover event
energies and grades from CTI-corrupted data. Our IDL code
is
available and there is an ApJ
Letter giving a brief description of our method. The latest
results are posted at our CTI
Corrector Webpage.
UV/Optical Blocking Filter Calibration
ACIS Spectroscopy Array Filter
273 eV
522 eV
775 eV
273 eV
522 eV
775 eV
ACIS Imaging Array Filter
We spatially and spectrally mapped the ACIS UV/Optical Blocking Filters
at the University of Wisconsin Synchrotron
Radiation Center (SRC) as part of their
flight calibration. I managed a team of scientists, engineers, and
technicians at Penn State and MIT and worked with high-energy physicist
James MacKay and
the SRC staff to design and carry out suites of measurements on several
sets of aluminized Lexan and Polyimide thin films (made by Luxel
Corporation)
that block UV and visual radiation. These measurements provided the
basic criterion for choosing the filters to be installed in ACIS, just
in front of the focal
plane, to ensure that only X-radiation is detected by the CCDs. This
calibration effort involved five major institutions and produced the most
detailed
spatial maps ever obtained on such films.
The Swift Gamma Ray Burst Explorer
I am a co-investigator on the Swift
Gamma Ray Burst Explorer, a NASA MIDEX mission scheduled for launch
in 2003. I served as the
UV/Optical Telescope
Lead during the Phase A Concept Study.
Most publications are available from astro-ph or ADS. Some upcoming papers are:
L. K. Townsley, P. S. Broos, G. Chartas, E. Moskalenko, J. A. Nousek, and G. G. Pavlov 2002, "Simulating CCDs for the Chandra Advanced CCD Imaging Spectrometer," Nuclear Instruments and Methods in Physics Research, Section A, in press (astro-ph/0111003)
L. K. Townsley, P. S. Broos, J. A. Nousek, and G. P. Garmire 2002, "Modeling Charge Transfer Inefficiency in the Chandra Advanced CCD Imaging Spectrometer," Nuclear Instruments and Methods in Physics Research, Section A, in press (astro-ph/0111031)