Source Region Per-Stack Detections Events Files (regevt3.fits)
The source region stack events files are the bases for calculations of numerous master source properties, such as the tabulated photometric fluxes and modelflux values. Because it is a stack events list, this type of events list may include events from multiple observations, the full list of which are included in the [EVENTS] header.
The source region stack events file consists of a single FITS format events file for source regions of each stack of observations; it is the result of applying a rectangular SKY region filter to the corresponding full-field event file for the stack of observations. The rectangular SKY region filter is equal in size to the background region of interest (ROI) corresponding to the detected source region.
The good time intervals (GTIs) associated with source region event data are included as additional FITS HDUs (CXC Data Model blocks) in the source region FITS event file. For an events file containing ACIS data, there is a GTI block for each ACIS CCD included in the source region; there is a single GTI block for an event file containing HRC data.
The stacked observations region events FITS file is named: 〈i〉〈s〉〈stkpos〉_〈stkver〉N〈v〉_〈r〉_regevt3.fits
where 〈i〉 is the instrument designation; 〈s〉 is the data source; 〈stkpos〉 is the position component of the stack name, formatted as "Jhhmmsss{p|m}ddmmss"; 〈stkver〉 is the 3-digit version component of the stack name, formatted with leading zeros; 〈v〉 is the data product version number; and 〈r〉 is the region ID, formatted as "rnnnn", where nnnn is the 4-digit region number, formatted with leading zeros.
Example
An example stack source regevt3 file from release 2.1 is:
unix% dmlist acisfJ1348473p263535_002N029_r0012_regevt3.fits blocks -------------------------------------------------------------------------------- Dataset: acisfJ1348473p263535_002N029_r0012_regevt3.fits -------------------------------------------------------------------------------- Block Name Type Dimensions -------------------------------------------------------------------------------- Block 1: PRIMARY Null Block 2: EVENTS Table 15 cols x 38819 rows Block 3: GTI7 Table 2 cols x 29 rows Block 4: GTI5 Table 2 cols x 29 rows Block 5: GTI6 Table 2 cols x 46 rows Block 6: GTI3 Table 2 cols x 44 rows Block 7: GTI2 Table 2 cols x 61 rows Block 8: GTI1 Table 2 cols x 15 rows Block 9: GTI0 Table 2 cols x 15 rows Block 10: MASK Image Byte(128x95)
This particular observation can be viewed with ds9 using a command similar to the following, which creates the following figure:
unix% ds9 acisfJ1348473p263535_002N029_r0012_regevt3.fits \
-mask transparency 85 \
-mask "acisfJ1348473p263535_002N029_r0012_regevt3.fits[MASK]" \
-zoom 4 -pan to 4434 3575 \
-region acisfJ1348473p263535_002N029_r0012_reg3.fits \
-bin factor 1 \
-scale log
Region event file
![[The ds9 image viewer shows the image data containing a source in the center of the field, along with a green ellipse region covering most of the source counts. The source counts are covered by a transparent red color indicating the location of the mask region.]](imgs/acisfJ1348473p263535_r0012_regevt3.png)