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ROSAT Guest Observer Facility

HRI SOURCE FLAG DESCRIPTION

General Introduction

Below is an outline of how the source flags are defined. Note that criteria for setting flags may differ between the PSPC and the HRI. Examples of some of the flags are available as GIF images.

Source flags can be set automatically using a standard criterion, while other flags can only be set after visual inspection.

Note that setting one flag may often set one or more subordinate flags. For example, setting the confused flag for a source will also set the position suspect flag.

The list of source flags and their meanings for HRI observations

CONFUSED
close sources confused detect. For example, 2 strong sources which lie close together may be detected as one source by the detection algorithm. This error becomes more likely as the off-axis angle increases since the point-spread function widens as the edge of the field of view is approached.

  • abbreviation: c
  • manner of flagging: visual inspection
  • subordinate flags set:INTEN_SUSP, LTC_SUSP, POS_SUSP, VARFLG_SUSP
  • hri example of source with CONFUSED flag set

    The source at the bottom of the image has the c flag set to True since it is probably a single source which has been detected as 2 separate sources by the detection algorithm.

DET_STRUCT
Source near a detector structure. For the HRI this means that the source is near the edge of the detector. All sources with EPI > 0.01 have the DET_STRUCT flag set to True

  • abbreviation: d
  • manner of flagging: automatic
  • subordinate flags set:INTEN_SUSP, LTC_SUSP, POS_SUSP, VARFLG_SUSP
  • hri example of source with DET_STRUCT flag set.

    Source 5 in the upper right of the image has the d flag set to True since it has a value of EPI > 0.01.

EXTENDED
Source appears extended. Generally set for galaxies, supernova remnants, etc. For the HRI, all sources with SIZ_COR > 1.2 have the EXTENDED flag set to True

  • abbreviation: e
  • manner of flagging: automatic
  • subordinate flags set:INTEN_SUSP, LTC_SUSP, POS_SUSP, VARFLG_SUSP
  • hri example of source with EXTENDED flag set

FALSE_DET
Reality of the source is doubtful.

  • abbreviation: f
  • manner of flagging: visual inspection
  • subordinate flags set:INTEN_SUSP, LTC_SUSP, POS_SUSP, VARFLG_SUSP
  • hri example of source with FALSE_DET flag set.

    The two purple sources in this image were flagged as false since in the opinion of the quality inspector they did not seem to be real.

INTENS_SUSP
The derived source count rate may be in error. This flag is set if the CONFUSED, DET_STRUCT, EXTENDED, FALSE_DET, MULT_DET, POS_SUSP, or ASSOCIATED flags are set

LTC_SUSP
The derived source lightcurve may be in error. This flag is set if the CONFUSED, DET_STRUCT, EXTENDED, FALSE_DET, MULT_DET, POS_SUSP, or ASSOCIATED flags are set. Since there are no source lightcurves currently provided for the HRI, this flag has little meaning at present.

MULT_DET
Complex emission split into individual sources. For example, spatial intensity fluctuations in the brightness distribution of a supernova remnant may be detected as individual sources by the detection algorithm. Similarly, spatial brightness fluctuations in the wings of the psf of a strong point source may be detected as individual sources.

  • abbreviation: m
  • manner of flagging: visual inspection
  • subordinate flags set:INTEN_SUSP, LTC_SUSP, POS_SUSP, VARFLG_SUSP
  • hri example of source with MULT_DET flag set.

    The bright source in the center of the field is LMC X-1. The wings of the psf has been detected as "real" individual sources by the source detect algorithm. These sources have their MULT_DET flag set to True.

NOT_CHECKED
This source has not been checked. Currently any source with signal-to-noise ratio < 4 is ignored.

  • abbreviation: n
  • manner of flagging: automatic
  • subordinate flags set:none
  • hri example of source with NOT_CHECKED flag set
POS_SUSP
The derived source position may be in error. This flag is set if the CONFUSED, DET_STRUCT, EXTENDED, FALSE_DET, MULT_DET, or ASSOCIATED flags are set. This flag may also be set by visual inspection, i.e. if the detection algorithm derived a clearly incorrect position for a real source.

  • abbreviation: p
  • manner of flagging: subordinate or visual inspection
  • subordinate flags set:INTEN_SUSP, LTC_SUSP, VARFLG_SUSP
  • hri example of source with POS_SUSP flag set.

    Source 5 in the upper right of the image has the d flag set so the p flag is also set.

ASSOCIATED
A source which has a nearby (but resolved) neighbor has the associated flag set to True. For the HRI the ASSOCIATED flag is set to True if either of 2 cases hold: 1) the distance between that source and any neighbor is less than the sum of twice the 50% point spread function radius for the source and the neighbor; or 2) if SIZCOR > 1.2 for the neighbor and the distance between the source and the center of the extended circle for the neighbor is less than the radius of the extended circle plus twice the 50% radius of the psf of the source.

  • abbreviation: a
  • manner of flagging: automatic
  • subordinate flags set:INTEN_SUSP, LTC_SUSP, VARFLG_SUSP
  • hri example of source with ASSOCIATED flag set.

    Source 140 in the left part of the image failed the above criteria and therefore its ASSOCIATED flag was set to True.

VARFLG_SUSP
The derived source variability flag may be in error. VARFLG_SUSP is set if the CONFUSED, DET_STRUCT, EXTENDED, FALSE_DET, MULT_DET, POS_SUSP, or ASSOCIATED flags are set.

UN_UNIQUE
The HRI processing software runs a source detection using detect cells of various sizes. The UN_UNIQUE flag is set to True if the source was matched with another source with a smaller detect cell size.

  • abbreviation: u
  • manner of flagging: automatic
  • subordinate flags set: none
  • hri example of source with UN_UNIQUE flag set