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Last modified: 7 June 2010
Where are the PDFs?

Compute Net Counts, Rate, or Flux for Point Sources

CIAO 4.2 Science Threads



Overview

Last Update: 7 Jun 2010 - use dmextract to get counts in source and background apertures; minor related adjustments to screen output

Synopsis:

The tool aprates computes values and bounds for source intensity quantities (net counts, source rate, photon flux, energy flux) using counts and exposure data obtained in source and background apertures.

This thread runs aprates multiple times - from computing simple net counts to computing energy fluxes with limits - each building on the previous aprates command. If you know which quantities to calculate, you can just set the appropriate parameters and run aprates once.

aprates uses Bayesian statistics to compute the background-marginalized, posterior probability distribution for source intensity, assuming non-informative prior distributions for background and source intensity (for details on the algorithm, see the Background Marginalized X-ray Source Intensity memo). The posterior distribution can be used to determine intensity value and confidence bounds or intensity upper limit.

Read this thread if:

you want to calculate net counts, source rate, photon flux, and/or energy flux for ACIS or HRC data.

Related Links:




Contents



Get Started

Sample ObsID used: 313 (ACIS-S/M31)

File types needed: reg3; regevt3; regexp3; psf3

Downloading the data

This thread uses level=3 data products which were downloaded from the the Chandra Source Catalog. These files are for the broad band (0.5-7.0 keV) of region_id=1 in ObsID 313:

acisf00313_000N001_r0001b_psf3.fits
acisf00313_000N001_r0001b_regexp3.fits
acisf00313_000N001_r0001_reg3.fits
acisf00313_000N001_r0001_regevt3.fits

To download these files:

  • Launch CSCView, the CSC GUI.

  • Search for the ObsID and region:

    From the "Standard Queries" list, select and drag "Standard Search Criteria → Search by Identification Information" to the "Search Criteria" box. Set the value of o.obsid to "313".

    In the "Source Properties" list, expand the menus "Source Observations → Detected Source Properties → Observation-Specific Identification Information". Select "region_id" and drag it to the "Search Criteria" box. Set the value of o.region_id to "1".

    Make sure there is at least one property in the "Result Set", e.g. add "Master Sources → Source Name → name".

    Click "Search". The GUI will switch to the "Results" tab and list the results returned.

  • Download the data files:

    Highlight the returned row (there should only be one, as we searched for a specific region number). In the "Data Products" list, control-click to select these four products:

    • Full Field: evt3
    • Source Region: regevt3, srcreg, and Point Spread Functions → psf_b.

    Click "Search". The GUI will switch to the "Products" tab and list the filenames found.

    Click "Download" to download a tarfile containing these files.


Syntax used in this thread

All the input to the aprates tool is obtained from the values set in the parameter file. That is, the tool doesn't read an event file or other data file to obtain the values. The input parameter values are determined by querying different data files before running aprates.

To avoid writing out many intermediate files, this thread uses a syntax with Unix pipes ("|") to use the output of one tool as the input to another without creating a physical file. For instance, this command does a calculation on the energy column with dmtcalc and then runs dmstat on the output:

unix% dmtcalc file.fits - expression="energy=1.6e-12*energy" | dmstat "-[cols energy]" verbose=0

This is equivalent to running two separate commands:

unix%  dmtcalc file.fits out.fits expression="energy=1.6e-12*energy" 
unix%  dmstat "out.fits[cols energy]" verbose=0

but the file, out.fits is never written to disk.



Displaying the Source and Background Regions

The source and background regions are stored as extensions of the reg3.fits file:

unix% dmlist acisf00313_000N001_r0001_reg3.fits blocks

--------------------------------------------------------------------------------
Dataset: acisf00313_000N001_r0001_reg3.fits
--------------------------------------------------------------------------------

     Block Name                          Type         Dimensions
--------------------------------------------------------------------------------
Block    1: PRIMARY                        Null
Block    2: SRCREG                         Table         5 cols x 1        rows
Block    3: BKGREG                         Table         5 cols x 2        rows

The ds9 command-line options are used to display them on the data, as shown in Figure 1.

unix% ds9 acisf00313_000N001_r0001_regevt3.fits -region acisf00313_000N001_r0001_reg3.fits \
      acisf00313_000N001_r0001_regevt3.fits -region "acisf00313_000N001_r0001_reg3.fits[bkgreg]" &
[Thumbnail image: Source and background regions displayed on the event file in separate ds9 frames.]

[Version: full-size]

[Print media version: Source and background regions displayed on the event file in separate ds9 frames.]

Figure 1: Regions overlaid on the image

The source region (top frame) is defined as an ellipse. The background region (bottom frame) is defined by two ellipses, the larger one excluding a smaller one to block any source counts from the background region area. Both regions are centered at (x,y)=(4164.807, 3602.933).



Net Source Counts

When the minimum number of parameters is set, aprates obtains net source counts and errors. The parameters required for this case are:

  • the number of counts in the source and background apertures: n and m
  • their geometric areas: A_s and A_b
  • their psf fractions: alpha and beta

Counts in source and background apertures

A number of different CIAO tools can be used to determine the area and number of events in apertures. These tools may yield slightly different results, depending on whether one starts with an event list or image. Results from event lists are more accurate, since event locations are typically known to finer resolution that a pixel size, and areas can be determined analytically for simple apertures. For images, aperture counts and areas are determined from those pixels whose centers fall within the aperture. We recommend the use of dmextract if an event list is available.

The number of counts in the source (n) and background (m) apertures and the areas of both apertures are found by running dmextract on the regevt3.fits file with the source and background regions. The energy range of the events is restricted to the broad band (0.5-7.0 keV):

unix%  dmextract \
       "acisf00313_000N001_r0001_regevt3.fits[energy=500:7000][bin sky=region(acisf00313_000N001_r0001_reg3.fits)]" \
       outfile=- \
       bkg="acisf00313_000N001_r0001_regevt3.fits[energy=500:7000][bin sky=region(acisf00313_000N001_r0001_reg3.fits[bkgreg])]" |\
       dmlist -"[col counts, area,bg_counts,bg_area]" data,clean
  
#  COUNTS   AREA              BG_COUNTS   BG_AREA
   141.0    196.6885375977    9.0         4720.50

There are 141 source counts (n=141) and 9 background counts (m=9). The source area is 196.689 pixels (A_s=196.689) and the background area is 4720.50 pixels (A_b=4720.50).


PSF fractions in source and background apertures

The PSF fraction in the source (alpha) and background (beta) apertures is found by running dmstat on the psf3.fits file with the source and background regions:

unix% dmstat \
      acisf00313_000N001_r0001b_psf3.fits"[sky=region(acisf00313_000N001_r0001_reg3.fits)]" \
      centroid=no verbose=0

unix% pget dmstat out_sum
0.95296573744

unix% dmstat \
      acisf00313_000N001_r0001b_psf3.fits"[sky=region(acisf00313_000N001_r0001_reg3.fits[bkgreg])]" \
      centroid=no verbose=0

unix% pget dmstat out_sum
0.028613533096

The PSF fraction in the source aperture is 0.953 (alpha=0.953) and the PSF fraction in the background aperture is 0.029 (beta=0.029).


Run aprates to compute net counts

To summarize the parameter values that have been determined:

  • n=141
  • m=9
  • A_s=196.689
  • A_b=4720.50
  • alpha=0.953
  • beta=0.029

All the other parameters for aprates are set to a value of 1. The confidence region (conf) value is left at the default value of 0.68. The output file will be named aprates_netcts.par.

The tool is run with mode=h to suppress prompting for parameter values.

unix% punlearn aprates
unix% pset aprates n=141 m=9
unix% pset aprates A_s=196.689 A_b=4720.50
unix% pset aprates alpha=0.953 beta=0.029
unix% pset aprates T_s=1 E_s=1 eng_s=1 flux_s=1 T_b=1 E_b=1 eng_b=1 flux_b=1 
unix% pset aprates outfile=aprates_netcts.par

unix% aprates mode=h
# aprates (CIAO 4.2): WARNING: Large number of counts, just using Gaussian pdf

The warning indicates that Gaussian statistics were used instead of Poisson statistics. This is controlled by the max_counts parameter: when n+m > max_counts, Gaussian statistics are used.

The output file is in parameter file format, which makes it possible to query the output values with the tool pget:

unix% pget aprates_netcts.par src_cnts src_cnts_err_lo src_cnts_err_up
147.748
135.396
160.224

The net counts value is 147.748, and the 68% confidence region extends from 135.396 to 160.224.

The full output file, aprates_netcts.par, is included at the end of the thread. Note that while the output file contains entries for rates and fluxes, they are just the net count values repeated.



Net Count Rate

By setting the exposure times in the source (T_s) and background (T_b) apertures, the net source rate and errors will be computed.

For this example, the exposure time is the same for the source and background since they come from the same file:

unix% dmkeypar acisf00313_000N001_r0001_regevt3.fits LIVETIME echo+
5977.7355472452

The exposure time is 5977.74 s.

Since this is building on the previous run of aprates, it is only necessary to set the additional parameters and to change the output file name:

unix% pset aprates T_s=5977.74 T_b=5977.74
unix% pset aprates outfile=aprates_netrate.par

unix% aprates mode=h
# aprates (CIAO 4.2): WARNING: Large number of counts, just using Gaussian pdf

unix% pget aprates_netrate.par src_rate src_rate_err_lo src_rate_err_up
0.0247163
0.02265
0.0268035

The net rate value is 0.0247163 ct/s, and the 68% confidence region extends from 0.02265 to 0.0268035.

The full output file, aprates_netrate.par, is included at the end of the thread.



Net Photon Flux

By setting the average effective exposures (in cm^2-s) in the source (E_s) and background (E_b) apertures, the net photon flux and errors will be computed.

The average effective exposures is found by running dmstat on the regexp3.fits file with the source and background regions:

unix% dmstat \
      acisf00313_000N001_r0001b_regexp3.fits"[sky=region(acisf00313_000N001_r0001_reg3.fits)]" \
      centroid=no verbose=0

unix% pget dmstat out_mean
2308338.2013

unix% dmstat \
      acisf00313_000N001_r0001b_regexp3.fits"[sky=region(acisf00313_000N001_r0001_reg3.fits[bkgreg])]" \
      centroid=no verbose=0

unix% pget dmstat out_mean
2058975.0111

The average effective exposure in the source region is 2308338.2013 cm^2-s (E_s=2308338.2013) and in the background region is 2058975.0111 cm^2-s (E_b=2058975.0111).

Since this is building on the previous run of aprates, it is only necessary to set the additional parameters and to change the output file name:

unix% pset aprates E_s=2308338.2013 E_b=2058975.0111
unix% pset aprates outfile=aprates_netflux.par

unix% aprates mode=h
# aprates (CIAO 4.2): WARNING: Large number of counts, just using Gaussian pdf

unix% pget aprates_netflux.par photflux_aper photflux_aper_err_lo photflux_aper_err_up
6.40e-5
5.86e-5
6.94e-5

The net photon flux is 6.40e-05 photons/cm^2-sec, and the 68% confidence region extends from 5.86e-05 to 6.94e-05.

The full output file, aprates_netflux.par, is included at the end of the thread.



Net Energy Flux

There are two options for calculating the net energy flux with aprates: using the average photon energies (in ergs) or using the average of photon effective exposure (in ergs/cm^2-s).

from average photon energies

By setting the average photon energies (in ergs) in the source (eng_s) and background (eng_b) apertures, the net energy flux and errors will be computed.

The counts in the apertures are filtered from the file regevt3.fits file with the source and background regions. The energy range of the events is restricted to the broad band (0.5-7.0 keV). The event energies are first converted to ergs using dmtcalc, and the average event energies in the apertures are then computed using dmstat.

For the source aperture:

unix% dmtcalc \
      "acisf00313_000N001_r0001_regevt3.fits[energy=500:7000,sky=region(acisf00313_000N001_r0001_reg3.fits)]" \
      - expression="energy=1.6e-12*energy" | dmstat "-[cols energy]" verbose=0

unix% pget dmstat out_mean
2.5579239786e-09

For the background aperture:

unix% dmtcalc \
      "acisf00313_000N001_r0001_regevt3.fits[energy=500:7000,sky=region(acisf00313_000N001_r0001_reg3.fits[bkgreg])]" \
      - expression="energy=1.6e-12*energy" | dmstat "-[cols energy]" verbose=0

unix% pget dmstat out_mean
4.2743555979e-09

The average photon energies in the source region is 2.56e-09 ergs (eng_s=2.56e-09) and in the background region is 4.27e-09 ergs (eng_b=4.27e-09).

Note that when using this option for computing energy flux, both average exposure (E_s, E_b) and average event energy (eng_s, eng_b) must be input.

All the parameters of aprates are set to the previously-determined values. The output file is named aprates_eflux.par.

unix% punlearn aprates
unix% pset aprates n=141 m=9
unix% pset aprates A_s=196.689 A_b=4720.50
unix% pset aprates alpha=0.953 beta=0.029
unix% pset aprates T_s=1 E_s=1 eng_s=1 flux_s=1 T_b=1 E_b=1 eng_b=1 flux_b=1 
unix% pset aprates T_s=5977.74 T_b=5977.74
unix% pset aprates E_s=2308338.2013 E_b=2058975.0111
unix% pset aprates eng_s=2.56e-09 eng_b=4.27e-09
unix% pset aprates outfile=aprates_flux.par

unix% aprates mode=h
# aprates (CIAO 4.2): WARNING: Large number of counts, just using Gaussian pdf

unix% pget aprates_flux.par flux_aper flux_aper_err_lo flux_aper_err_up
1.63e-13
1.50e-13
1.77e-13

The net energy flux is 1.63e-13 ergs/cm^2-sec, and the 68% confidence region extends from 1.50e-13 to 1.77e-13.

The full output file, aprates_flux.par, is included at the end of the thread.


from average of photon effective exposure

An alternate method of computing the net energy flux and errors is to set the average of photon energy/effective exposure (in ergs/cm^2-s) in the source (flux_s) and background (flux_b) apertures.

This computation is preferable to the one using eng_s and eng_b because it more properly weights the contribution of higher energy photons, which, though few, may dominate the energy flux.

The counts in the apertures are filtered from the file regevt3.fits file with the source and background regions. The energy range of the events is restricted to the broad band (0.5-7.0 keV). The event fluxes are first computed using eff2evt, then the average of this quantity in the apertures is found with dmstat.

For the source aperture:

unix% eff2evt \
      "acisf00313_000N001_r0001_regevt3.fits[energy=500:7000][sky=region(acisf00313_000N001_r0001_reg3.fits)]" - | \
      dmstat -"[cols flux]" verbose=0

unix% pget dmstat out_mean
9.8048216059e-16

For the background aperture:

unix% eff2evt \
      "acisf00313_000N001_r0001_regevt3.fits[energy=500:7000][sky=region(acisf00313_000N001_r0001_reg3.fits[bkgreg])]" - | \
      dmstat -"[cols flux]" verbose=0

unix% pget dmstat out_mean
2.2342449512e-15

The average of photon energy/effective exposure in the source region is 9.81e-16 ergs/cm^2-s (flux_s=9.81e-16) and in the background region is 2.23e-15 (flux_b=2.23e-15).

All the parameters of aprates are set to the previously-determined values. The output file is named aprates_eflux.par.

unix% punlearn aprates
unix% pset aprates n=141 m=9
unix% pset aprates A_s=196.689 A_b=4720.50
unix% pset aprates alpha=0.953 beta=0.029
unix% pset aprates T_s=1 E_s=1 eng_s=1 flux_s=1 T_b=1 E_b=1 eng_b=1 flux_b=1 
unix% pset aprates T_s=5977.74 T_b=5977.74
unix% pset aprates E_s=2308338.2013 E_b=2058975.0111
unix% pset aprates flux_s=9.81e-16 flux_b=2.23e-15
unix% pset aprates outfile=aprates_eflux.par

unix% aprates mode=h
# aprates (CIAO 4.2): WARNING: Large number of counts, just using Gaussian pdf

unix% pget aprates_eflux.par eflux_aper eflux_aper_err_lo eflux_aper_err_up
1.44448e-13
1.32329e-13
1.56691e-13

The net energy flux is 1.4448e-13 ergs/cm^2-sec, and the 68% confidence region extends from 1.32329e-13 to 1.56691e-13.

The full output file, aprates_eflux.par, is included at the end of the thread.




Parameters for /home/username/cxcds_param/aprates_netcts.par



Parameters for aprates_netcts.par

     (src_cnts = 147.748)
(src_cnts_err_lo = 135.396)
(src_cnts_err_up = 160.224)
(src_cnts_conf = 0.680254)
(src_cnts_status = 0)
(src_cnts_signif = 11.8158)
(src_cnts_mode = 147.743)
     (src_rate = 147.743)
(src_rate_err_lo = 135.391)
(src_rate_err_up = 160.219)
(src_rate_conf = 0.680254)
(src_rate_status = 0)
(src_rate_signif = 11.8158)
(src_rate_mode = 147.743)
(photflux_aper = 147.743)
(photflux_aper_err_lo = 135.391)
(photflux_aper_err_up = 160.219)
(photflux_aper_conf = 0.680254)
(photflux_aper_status = 0)
(photflux_aper_signif = 11.8158)
(photflux_aper_mode = 147.743)
    (flux_aper = 147.743)
(flux_aper_err_lo = 135.391)
(flux_aper_err_up = 160.219)
(flux_aper_conf = 0.680254)
(flux_aper_status = 0)
(flux_aper_signif = 11.8158)
(flux_aper_mode = 147.743)
   (eflux_aper = 147.743)
(eflux_aper_err_lo = 135.391)
(eflux_aper_err_up = 160.219)
(eflux_aper_conf = 0.680254)
(eflux_aper_status = 0)
(eflux_aper_signif = 11.8158)
(eflux_aper_mode = 147.743)
           (_n = 141)
         (_A_s = 196.689)
       (_alpha = 0.953)
         (_T_s = 1)
         (_E_s = 1)
       (_eng_s = 1)
      (_flux_s = 1)
           (_m = 9)
         (_A_b = 4720.50)
        (_beta = 0.029)
         (_T_b = 1)
         (_E_b = 1)
       (_eng_b = 1)
      (_flux_b = 1)
         (mode = ql)
    


Parameters for /home/username/cxcds_param/aprates_netrate.par



Parameters for aprates_netrate.par

     (src_cnts = 147.743)
(src_cnts_err_lo = 135.391)
(src_cnts_err_up = 160.219)
(src_cnts_conf = 0.680254)
(src_cnts_status = 0)
(src_cnts_signif = 11.8158)
(src_cnts_mode = 147.743)
     (src_rate = 0.0247163)
(src_rate_err_lo = 0.02265)
(src_rate_err_up = 0.0268035)
(src_rate_conf = 0.680254)
(src_rate_status = 0)
(src_rate_signif = 11.8158)
(src_rate_mode = 0.0247155)
(photflux_aper = 147.743)
(photflux_aper_err_lo = 135.391)
(photflux_aper_err_up = 160.219)
(photflux_aper_conf = 0.680254)
(photflux_aper_status = 0)
(photflux_aper_signif = 11.8158)
(photflux_aper_mode = 147.743)
    (flux_aper = 147.743)
(flux_aper_err_lo = 135.391)
(flux_aper_err_up = 160.219)
(flux_aper_conf = 0.680254)
(flux_aper_status = 0)
(flux_aper_signif = 11.8158)
(flux_aper_mode = 147.743)
   (eflux_aper = 147.743)
(eflux_aper_err_lo = 135.391)
(eflux_aper_err_up = 160.219)
(eflux_aper_conf = 0.680254)
(eflux_aper_status = 0)
(eflux_aper_signif = 11.8158)
(eflux_aper_mode = 147.743)
           (_n = 141)
         (_A_s = 196.689)
       (_alpha = 0.953)
         (_T_s = 5977.74)
         (_E_s = 1)
       (_eng_s = 1)
      (_flux_s = 1)
           (_m = 9)
         (_A_b = 4720.50)
        (_beta = 0.029)
         (_T_b = 5977.74)
         (_E_b = 1)
       (_eng_b = 1)
      (_flux_b = 1)
         (mode = ql)
    


Parameters for /home/username/cxcds_param/aprates_netflux.par



Parameters for aprates_netflux.par

     (src_cnts = 147.743)
(src_cnts_err_lo = 135.391)
(src_cnts_err_up = 160.219)
(src_cnts_conf = 0.680254)
(src_cnts_status = 0)
(src_cnts_signif = 11.8158)
(src_cnts_mode = 147.743)
     (src_rate = 0.0247155)
(src_rate_err_lo = 0.0226492)
(src_rate_err_up = 0.0268026)
(src_rate_conf = 0.680254)
(src_rate_status = 0)
(src_rate_signif = 11.8158)
(src_rate_mode = 0.0247155)
(photflux_aper = 6.40e-05)
(photflux_aper_err_lo = 5.86e-05)
(photflux_aper_err_up = 6.94e-05)
(photflux_aper_conf = 0.680254)
(photflux_aper_status = 0)
(photflux_aper_signif = 11.8117)
(photflux_aper_mode = 6.39831e-05)
    (flux_aper = 6.39831e-05)
(flux_aper_err_lo = 5.86321e-05)
(flux_aper_err_up = 6.93881e-05)
(flux_aper_conf = 0.680254)
(flux_aper_status = 0)
(flux_aper_signif = 11.8117)
(flux_aper_mode = 6.39831e-05)
   (eflux_aper = 147.743)
(eflux_aper_err_lo = 135.391)
(eflux_aper_err_up = 160.219)
(eflux_aper_conf = 0.680254)
(eflux_aper_status = 0)
(eflux_aper_signif = 11.8158)
(eflux_aper_mode = 147.743)
           (_n = 141)
         (_A_s = 196.689)
       (_alpha = 0.953)
         (_T_s = 5977.74)
         (_E_s = 2.30834e+06)
       (_eng_s = 1)
      (_flux_s = 1)
           (_m = 9)
         (_A_b = 4720.50)
        (_beta = 0.029)
         (_T_b = 5977.74)
         (_E_b = 2.05898e+06)
       (_eng_b = 1)
      (_flux_b = 1)
         (mode = ql)
    


Parameters for /home/username/cxcds_param/aprates_flux.par



Parameters for aprates_flux.par

     (src_cnts = 147.743)
(src_cnts_err_lo = 135.391)
(src_cnts_err_up = 160.219)
(src_cnts_conf = 0.680254)
(src_cnts_status = 0)
(src_cnts_signif = 11.8158)
(src_cnts_mode = 147.743)
     (src_rate = 0.0247155)
(src_rate_err_lo = 0.0226492)
(src_rate_err_up = 0.0268026)
(src_rate_conf = 0.680254)
(src_rate_status = 0)
(src_rate_signif = 11.8158)
(src_rate_mode = 0.0247155)
(photflux_aper = 6.39831e-05)
(photflux_aper_err_lo = 5.86321e-05)
(photflux_aper_err_up = 6.93881e-05)
(photflux_aper_conf = 0.680254)
(photflux_aper_status = 0)
(photflux_aper_signif = 11.8117)
(photflux_aper_mode = 6.39831e-05)
    (flux_aper = 1.63e-13)
(flux_aper_err_lo = 1.50e-13)
(flux_aper_err_up = 1.77e-13)
(flux_aper_conf = 0.680254)
(flux_aper_status = 0)
(flux_aper_signif = 11.7864)
(flux_aper_mode = 1.63466e-13)
   (eflux_aper = 147.743)
(eflux_aper_err_lo = 135.391)
(eflux_aper_err_up = 160.219)
(eflux_aper_conf = 0.680254)
(eflux_aper_status = 0)
(eflux_aper_signif = 11.8158)
(eflux_aper_mode = 147.743)
           (_n = 141)
         (_A_s = 196.689)
       (_alpha = 0.953)
         (_T_s = 5977.74)
         (_E_s = 2.30834e+06)
       (_eng_s = 2.56e-09)
      (_flux_s = 1)
           (_m = 9)
         (_A_b = 4720.50)
        (_beta = 0.029)
         (_T_b = 5977.74)
         (_E_b = 2.05898e+06)
       (_eng_b = 4.27e-09)
      (_flux_b = 1)
         (mode = ql)
    


Parameters for /home/username/cxcds_param/aprates_eflux.par



Parameters for aprates_eflux.par

     (src_cnts = 147.743)
(src_cnts_err_lo = 135.391)
(src_cnts_err_up = 160.219)
(src_cnts_conf = 0.680254)
(src_cnts_status = 0)
(src_cnts_signif = 11.8158)
(src_cnts_mode = 147.743)
     (src_rate = 0.0247155)
(src_rate_err_lo = 0.0226492)
(src_rate_err_up = 0.0268026)
(src_rate_conf = 0.680254)
(src_rate_status = 0)
(src_rate_signif = 11.8158)
(src_rate_mode = 0.0247155)
(photflux_aper = 6.39831e-05)
(photflux_aper_err_lo = 5.86321e-05)
(photflux_aper_err_up = 6.93881e-05)
(photflux_aper_conf = 0.680254)
(photflux_aper_status = 0)
(photflux_aper_signif = 11.8117)
(photflux_aper_mode = 6.39831e-05)
    (flux_aper = 6.39831e-05)
(flux_aper_err_lo = 5.86321e-05)
(flux_aper_err_up = 6.93881e-05)
(flux_aper_conf = 0.680254)
(flux_aper_status = 0)
(flux_aper_signif = 11.8117)
(flux_aper_mode = 6.39831e-05)
   (eflux_aper = 1.44448e-13)
(eflux_aper_err_lo = 1.32329e-13)
(eflux_aper_err_up = 1.56691e-13)
(eflux_aper_conf = 0.680254)
(eflux_aper_status = 0)
(eflux_aper_signif = 11.7733)
(eflux_aper_mode = 1.44448e-13)
           (_n = 141)
         (_A_s = 196.689)
       (_alpha = 0.953)
         (_T_s = 5977.74)
         (_E_s = 2.30834e+06)
       (_eng_s = 1)
      (_flux_s = 9.81e-16)
           (_m = 9)
         (_A_b = 4720.50)
        (_beta = 0.029)
         (_T_b = 5977.74)
         (_E_b = 2.05898e+06)
       (_eng_b = 1)
      (_flux_b = 2.23e-15)
         (mode = ql)
    

History

15 Dec 2008 New for CIAO 4.1
01 Jul 2009 added instructions on download the data from the CSC
27 Jul 2009 Bayesian statistics information added to the Overview
09 Feb 2010 updated for CIAO 4.2: minor changes to screen output
23 Feb 2010 eff2evt can handle file filters, so the dmcopy steps and temporary files aren't necessary (In "Net Energy Flux: from average of photon effective exposure" section)
09 Mar 2010 added a link to the Chandra Source Catalog, which contains reference fluxes for many sources
07 Jun 2010 use dmextract to get counts in source and background apertures; minor related adjustments to screen output

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Last modified: 7 June 2010