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Chandra Electronic Bulletin No. 78

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Chandra      |             CC     XX XX    OO OO          | CXC
Electronic   |            CC       XXX    OO   OO         | Number 78
Bulletin     |             CC     XX XX    OO OO          | 16 December 2008
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Welcome to the Chandra X-ray Center's Electronic News Bulletin Number 78.

CXC Web site: cxc.harvard.edu

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1.  Chandra Cycle 11 Call for Proposals

2.  New HRC-S Gain Map and LETG/HRC-S Background Filter 

3.  A New Merged Dataset of the Chandra Deep Field North

4.  CIAO 4.1 and CALDB 4.1 released 15 December 2008 


Item 1.  Chandra Cycle 11 Call for Proposals  

The CXC is pleased to announce the release of the Chandra Cycle 11 Call for 
Proposals (CfP). The Call for Proposals, proposal planning software,
preliminary instrument effective areas and general information are 
posted on the "Proposer" web page at the CXC website:


Proposals are due: 17 March 2009

Hardcopy documents are available on request to the CXC helpdesk.

The Proposers' Observatory Guide (POG) will be released in mid-January 
along with updated effective areas as described below:

Effective Area Files
We plan to release updates within about a month of this CfP 
which will impact the effective areas of all instruments. At that time, we 
will provide an updated CALDB and Proposers' Observatory Guide (POG).

The updates will affect PIMMS, Effective Area Viewer and proposal 
threads which use this software, as well as all CIAO software which 
accesses instrument effective areas in the CALDB. Information on the status 
of this update and about the updated effective area files will be 
posted prominently on the Proposer Webpages and on the Cycle 11 Effective 
Area download webpages as well as described in the POG.
In most cases proposal and observation planning will not be impacted,
so that proposers may start by using the tools released with this Cycle 11 
CfP. However we recommend that proposers revisit count rate and other 
or simulations after we have issued the updates and before they submit 
their proposals.

The updates involve two issues. The first adjusts the time dependence of the 
contamination buildup on the ACIS Optical Blocking Filters (OBF) and 
the second better takes into account a small level of contaminant on the 
Chandra Telescope (HRMA) that appears to have been present prior to launch. 

1) Contaminant Build up on the ACIS Optical Blocking Filter (OBF):
The primary impact of the change in ACIS filter modeling is to allow for more 
accurate extrapolation of throughput to future times, bringing it in-line with 
current measurements using the ACIS External Calibration Souce (ECS).
However, this change will not remove a current uncertainty in the filter 
throughput below ~500 eV. At the Carbon K-edge, (284 eV) the 
uncertainty would lead to systematically high, derived column densities
at a level ~1e20 cm^{-2}. For proposers, the lack of an accounting for
the additional optical depth results in over-estimated count rates at low 
energies. We will provide information and guidance to proposers as 
to the possible effects the remaining uncertainty in the <500 eV absorption 
will have on predicted feasibility determinations for Chandra proposals with 
the January release.

2) HRMA Effective Area:
The primary impact of the change in the telescope effective area is 
a lower effective area at low energies which will result in lower 
continuum-derived temperatures for high-temperature thermal sources 
such as clusters of galaxies, steeper derived power law slopes (~0.1)
and a few percent higher derived fluxes. In terms of estimates
for proposals, those made with the current release (i.e. before the January 
update) will over-estimate the low energy (<2 keV) count rate.


Item 2.  New HRC-S Gain Map and LETG/HRC-S Background Filter

A new HRC-S gain map and LETG/HRC-S background filter are available at
http://cxc.harvard.edu/contrib/letg/GainFilter/.  Because of gradual 
gain decrease in the HRC-S, the old background filter has lost much of 
its effectiveness.  The new time-dependent gain map and filter have 
several other improvements, and even old data will benefit from
reprocessing.  Up to 70% of the Level 2 background is removed with only
a 1.25% loss of X-ray events.  Users will need to download Perl-based 
software; implementation in CIAO is expected sometime in 2009.

Brad Wargelin
for the LETG Group


Item 3.  A New Merged Dataset of the Chandra Deep Field North   

A new merged dataset of the Chandra Deep Field North has been put
online, similar to the one for the Chandra Deep Field South that was
made available earlier this year.

Pointers for the CDFN merged data may be found at:


CDFS merged data:


CXC Data Systems


Item 4.   CIAO 4.1 and CALDB 4.1 released 15 December 2008 

The Chandra X-ray Center (CXC) is pleased to announce that version
4.1 of CIAO ("Chandra Interactive Analysis of Observations") and
version 4.1 of CALDB ("Calibration Database") are available for download

NOTE: CALDB 4.1 can only be used with CIAO 4.1 and CIAO 4.1 can only be 
used with CALDB 4.1.

CIAO 4.1 features a complete new version of  Sherpa, the modeling and
fitting package (http://cxc.harvard.edu/sherpa). This version gives
users a full access to internal data structures - within  the Python and
S-lang environments - that allows a great flexibility in data analysis
and modeling. There are several new features and upgrades since Sherpa
Beta; the About the Sherpa Release page
(http://cxc.harvard.edu/sherpa/about.html) highlights new items and
outlines differences  in comparison to Sherpa 3.4. Extensive
documentation upgrades were made both in the software package and on
the web site.

Other notable changes in CIAO 4.1 are:
     *enhancements and bug fixes in the Data Model ASCII kernel. Both
FITS and ASCII files are now accepted by most CIAO tools.

     *several new tools, which were initially developed for use with the
Chandra Source Catalog: aprates, dmellipse, eff2evt, lim_sens, mkpsfmap

     *significant work has been done on the tool wavdetect to fix the
bugs identified in CIAO 4.0: changing the falsesrc parameter value, a
lower limit on the sigthresh value, and limitations in the PSF information

     *the CIAO GUIs - prism, peg, and taskmonitor - have been rewritten
in Gtk. The prism rewrite includes several enhancements, such as
expanding vectors and arrays inline, tabbed frames to load multiple
files into a single prism window, and a basic GUI for customizing plots.

     *version 4 of the CALDB library, caldb4-module, and calquiz tool.
CIAO tools have been upgraded to use the new library and calibration

     *all the enhancements and bug fixes to the CIAO tools.

     *due to simplifications made to the behavior of lines, labels,
regions, and points in CIAO 4.1, the binary state files created by ChIPS
in CIAO 4.0 can not be read into CIAO 4.1 (an error message about an
incompatible version will be returned by when trying to do so).

Read the complete CIAO 4.1 release notes, including the section "How
CIAO 4.1 and CALDB 4.1 Affect Your Analysis" at:

We plan to support CIAO3.4 and CALDB 3.X for the near future
The CIAO3.4 web site is now accessible at:
while the CALDB3.X is accessible at


In tandem with CIAO 4.1 is the release of the Chandra Calibration
Database version 4.1.

CALDB 4.1.0 is the first public release and official installation of the
Chandra CalDB4 directory, index, and interface software upgrade.
CalDB 4.1.0 includes:

     * ACIS -120C T_GAIN Epoch 35 updates (four new files covering Epoch
34 and 35).
     * ACIS -110C/-120C BI chip mkacisrmf input file for
NON-CTI-corrected data.
     * HRMA REEF version N0001 (Encircled Counts Fraction). This file is
employed specifically in the CIAO 4.1 tool "mkpsfmap."

CALDB 4.1 may *only* be used with CIAO 4.1.

Detailed information can be found in the Chandra
Calibration Database website at http://cxc.harvard.edu/caldb/


CIAO 4.1 is distributed for the following platforms:

      * Solaris 8 (SunOS5.8)
      * Fedora Core 4
      * Fedora Core 8
      * Mac OS X PowerPC 10.4
      * Mac OS X Intel 10.4 and 10.5

More details at http://cxc.harvard.edu/ciao/download/platforms.html


As always please send questions and requests for enhancements to the CXC
HELPDESK (http://cxc.harvard.edu/helpdesk/).

CIAO 4.1 is a collaborative effort between the SAO/CXC Science Data
Systems, the SAO/CXC Data Systems, and MIT/CXC personnel.

Antonella Fruscione (for the CIAO development team)


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