Glossary of the Tartarus Web Pages
GLOSSARY OF THE TARTARUS WEB PAGES
GIS IMAGE:
Exposure corrected and smoothed, combined GIS2+3 image in sky coordinates with a log scaling. The green circle marks the expected position of the target, based on the RA/DEC given by the observer.
Created by XIMAGE.
LIGHT CURVE:
Combined SIS0+1 light curve with 5760 sec binning. The background level has not been subtracted.
Created by LCURVE.
SPECTRUM:
Data from all four detectors, compared to a simple power law model (shown convoluted through the detector response). The fit was performed excluding the 5-7.5 keV band; these data were read back in to make the plot. The bottom panel shows the data/model ratio.
Created by XSPEC.
DETECTOR IMAGES:
Images of all four detectors (in detector coordinates) with a log scaling. The circles overlaid on the sky images show the regions from which the products were extracted.
Green circle: the source region to be included in the extraction
Red circle: the background region to be included in the extraction
Yellow circle: the region excluded from the extraction.
The source region is inside the green circle. The background region is
between the yellow dashed circle and the red circle. For the SIS instruments,
the background region includes everything in the NOMINAL chip except the
excluded regions (yellow).
All regions are centered on the centroid of
the source and have standard sizes, although some regions have been manually
edited.
Created by SAOTNG.
SOURCE DETECTION SIGNIFICANCE:
This number was calculated in the following way.
S = (Ts - Tb) / sqrt(Tb)
where Ts = total counts in the source region, and Tb = total counts in the background region normalized to the area of the source region (predicted counts in the source region without the source).
NOTE:
If S > 5, the position of the source is calculated by taking the brightest pixel in the source region (r = 3.5') of a smoothed image for each instrument. If S < 5, the central position of the extracting regions is taken from the PI (attitude file) and all the products are made from those extracting regions, so they may not correspond to any particular source
GENERAL INFORMATION:
Date: Date on which the observation was conducted.
Exposure: Total time in seconds the target was exposed to the detectors.
Duration: The time elapsed between the start and stop times of the observation. The actual exposure time is always shorter than this, because of periods during the observation when no useful on-source data are obtained.
RA: Right ascension of the source's centroid (J2000 coordinates).
DEC: Declination of the source's centroid (J2000 coordinates).
Mode: Clocking mode - how many CCD's were turned on during the observation. Data collection mode - FAINT, BRIGHT, BRIGHT2.
SPECTRAL INFORMATION:
The fit shown on the web page is a double power law fit with absorbtion.
Photon index: The exponential parameter, Gamma, in the simple power law model.
nH: Column density - density of the absorbing gas in the AGN.
nH(gal): Galactic column density - density of gas in our galaxy in the direction of the AGN.
Chi^2 / dof: Reduced chi-squared per degree of freedom for the simple power law fit.
Flux(0.5-2): SIS0 energy flux in the 0.5 keV to 2.0 keV band in erg/cm^2/sec, derived from a double power law fit. Not corrected for absorption.
Flux(2-10): SIS0 energy flux in the 2.0 keV to 10.0 keV band in erg/cm^2/sec, derived from a double power law fit. Not corrected for absorption.
SUMMED COUNT RATES:
All countrates were calculated from their corresponding light curves. All count rates are background subtracted. The amount of background subtracted was calculated using the BACKSCAL ratio of the source region to the background region. For region definitions see the sky images of individual detectors.
SIS full: SIS combined count rate of the full energy band (0.5 - 10.0 keV) from the source region.
SIS bgd: SIS combined count rate of the full energy band from the background region rescaled to the size of the source region.
SIS soft: SIS combined count rate of the soft energy band (0.5 - 2.0 keV) from the source region.
SIS hard: SIS combined count rate of the hard energy band (2.0 - 10.0 keV ) from the source region.
GIS full: GIS combined count rate of the full energy band from the source region.
GIS hard: GIS combined count rate of the hard energy band from the source region.
AGN IN THIS FIELD:
Veron 96 list of AGN in the near field of the target source. The list was obtained using the browse_extract.pl perl script which uses the webquery.pl perl script. The list is independent of this database or any ASCA observations.
CLICK HERE TO RETURN TO THE TARTARUS HOME PAGE
Tartarus Feedback:
Responsible Scientists, Jane Turner & Kirpal Nandra
tartarus@olegacy.gsfc.nasa.gov
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