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Chandra Electronic Announcement #69
CHANDRA ELECTRONIC ANNOUNCEMENT NUMBER 69

CXC Web site: cxc.harvard.edu

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Contents:

1. Upcoming July Chandra Science Workshop: 
Structure in Clusters and Groups of Galaxies in the Chandra Era 

2. CIAO bug: Incorrect GTIs when time-filtering grating data with
dmcopy opt=all 


----------------------------------------------------------------------
Item 1: Upcoming July Chandra Science Workshop: 
STRUCTURE IN CLUSTERS AND GROUPS OF GALAXIES IN THE CHANDRA ERA
======================================================================

Abstract submission is open for the Chandra-sponsored Science Workshop
entitled

STRUCTURE IN CLUSTERS AND GROUPS OF GALAXIES IN THE CHANDRA ERA

           July 12-14, 2011
at the DoubleTree Guest Suites in Boston, MA.

Please check the website at
        http://cxc.harvard.edu/cdo/xclust11
for full information, including invited speakers, accommodation
information, and a workshop poster suitable for advertising
the meeting at your institution!


    +++++++++++    DEADLINES    +++++++++++++
Wednesday, April 27, 2011
        Final deadline for contributed talk abstract submission

Wednesday, June 1, 2011
        Final deadline for general registration and poster abstract submission

MEETING ABSTRACT:

   Structure in Clusters and Groups of Galaxies in the Chandra Era

The 2011 Chandra Science Workshop focuses on structure within the hot
intracluster media (ICM) of resolved clusters and groups of
galaxies. This conference will celebrate the interface of observable
phenomena such as shocks, cold fronts, abundance variations, bubbles,
and jets with theory and interpretations related to cluster mergers,
sloshing, and AGN feedback, with an emphasis on joining Chandra
results with those from other missions and wavelengths. 


----------------------------------------------------------------------
Item 2: CIAO bug: Incorrect GTIs when time-filtering grating data with
dmcopy opt=all
======================================================================

The CIAO team has identified a bug which affects all ACIS and HRC
grating data analysis.  This bug is new in CIAO 4.3.

When a time filter is applied to a level=1.5 (evt1a.fits) or level=2
(evt2.fits) grating file *and* the dmcopy opt=all option is used, the
GTI block in the output file is not updated to reflect the correct
time range.

Time-related header keyword values - such as ontime, livetime, and
exposure - will be incorrect because they are calculated from the time
ranges in the GTI block.

This time-filtering is one of the standard reprocessing steps for
grating data, so anyone that has reprocessed a grating dataset in CIAO
4.3 is affected.


Workaround:

Run dmcopy without "opt=all" when apply any time filters.  Then run
dmappend to copy the grating REGION block onto the filtered output
file.

In this example, the time filter is an flt1.fits file from the
Archive.  The filter might also be supplied as a GTI file created with
the dmgti tool, an ASCII table, or a range specified on the command
line.


Standard syntax:
unix% dmcopy "evt1a.fits[EVENTS][@flt1.fits]" evt2.fits opt=all

Workaround syntax:
unix% dmcopy "evt1a.fits[EVENTS][@flt1.fits]" evt2.fits
unix% dmappend "evt1a.fits[region][subspace -time]"  evt2.fits

The subspace filter is necessary so that the GTIs aren't reapplied to
the output file, as explained in the dmappend caveat:
http://cxc.harvard.edu/ciao/bugs/dmappend.html


Note that grating data reprocessed with the chandra_repro script is
also affected by this bug.  We are working on a patch to the script
which will incorporate this workaround.

If you have any questions on the bug or this workaround, contact the
CXC HelpDesk for assistance:
http://cxc.harvard.edu/helpdesk/

----------------------------------------------------------------------


Last modified: 03/25/11

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