Source Region Per-Stack Detections Region Files (reg3.fits)

The per-stack detections source region file consists of a single FITS format region file with a block containing a region for each science energy band.

FITS HDUs (CXC Data Model blocks):

• ACIS:
  • ECF90REGB
  • ECF90REGU
  • ECF90REGS
  • ECF90REGM
  • ECF90REGH
• HRC:
  • ECF90REGW

The source regions for each energy band in the data blocks are the elliptical apertures for each source, defined as the ellipses that include the 90% encircled counts fraction of the PSF in each science energy band at the source location.

The per-observation detections stacked source region file consists of a single FITS format region file for each source region stack, which records the region description for the modified source region and the corresponding modified background region, in consecutive HDUs.

FITS HDUs (CXC Data Model blocks):

• SRCREG: elliptical region encompassing the source in the detection stack.
• BKGREG: elliptical annulus encompassing background around the source in the detection stack.

Stacked Region Observation Source and Background Regions

[Version: full-size]

Stacked Region Observation Source and Background Regions

An example of source region (left) and the background region for the source (right). The striked through sub-regions are excluded areas from the background.

The stacked source region FITS file is named: 〈i〉〈s〉〈stkpos〉_〈stkver〉N〈v〉_〈r〉_reg3.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.

Related Science Documents

• ahelp: dmregions
• ahelp: dmgroupreg
• ahelp: roi
• CIAO: Creating Source and Background Files
• CIAO: Using CIAO Region Files