Glossary of Terms

ASCA object name - Name of target object as specified in the OBJECT keyword in the attitude file.

Background Subtracted Counts - The best estimate of the number of source counts (Full or Full2 band) within the source region area on the detector image. This is the difference between the Source Region Counts and the Scaled Background Region Counts.

Background Subtracted Rate - Background Subtracted Counts (Full or Full2 band) divided by exposure time.

Custom regions - The Tartarus script t_cent usually defines the source and background extraction regions automatically. For some observing sequences, however, these regions were required to be defined manually. These "custom regions" were determined by-eye.

Dec - Declination in equatorial co-ordinates (J2000)

Detection Significance - Significance of the detection of the target object in the GIS2 sky image. A detection significance of 5 sigma corresponds to a false detection probability of 2.87e-7. Objects with a detection significance of at least 5 sigma are classified as detections.

Detector Images (Unsmoothed) - Images using detector co-ordinates with default binning. The SIS images are rebinned by a factor of 4 (6.35" per pixel) and the GIS images are unbinned (14.7" per pixel).

Detector Images (Smoothed) - Images using detector co-ordinates with default binning and then smoothing. The SIS images were initially binned by a factor of 4 (the default; 6.35" per pixel) and the GIS images were unbinned (14.7" per pixel). The images were then smoothed with a Gaussian kernel of 1 pixel standard deviation.

Energy Band (Full) - Spectral fitting conducted over the 0.6-10 keV (SIS) and 0.75-10 keV (GIS) bands. For events files and light curves the Full band refers to the 0.5-10 keV (SIS) and 0.75-10 keV (GIS) bands.

Energy Band (Full2) - For events files and light curves the Full2 band is sometimes used for the SIS and refers to the 0.6-10 keV band.

Energy Band (Hard) - Spectral fitting conducted over the 2.0-10 keV bands for both SIS and GIS. For events files and light curves the Hard band refers to the 2.0-10 keV band.

Energy Band (Soft) - Spectral fitting conducted over the 0.6-2.0 keV (SIS) and 0.75-2.0 keV (GIS) bands. For events files and light curves the Soft band refers to the 0.5-2.0 keV and is available for the SIS only.

Energy Band (Soft2) - For events files and light curves the Soft2 band is sometimes used for the SIS and refers to the 0.6-2.0 keV band.

Event threshold - The "effective" event threshold for each SIS instrument is the higher value between the actual event threshold and the lower discriminator value. If the effective event threshold changes during the observation, then the lowest energy used should be 0.6 keV. In this case, the source counts given in the "Detector Images, Extraction Regions and Counts" section are from the Full2 (0.6-10 keV) and Soft2 (0.6-2.0 keV) bands. Also, if the effective event threshold changes during an observation, then the Full2 and Soft2 bands (instead of the Full and Soft bands) should be used for light curves.

Galactic N_H - The weighted average neutral Hydrogen column density in the direction of the target, as calculated with the nH FTOOL. A web version is also available.

GIS2 - One of the two gas-imaging spectrometers. Referred to as detector number "2".

GIS3 - One of the two gas-imaging spectrometers. Referred to as detector number "3".

GIS3 channels - All GIS3 data obtained between 1994 February 10 and April 8 had only 128 spectral channels instead of the normal 1024 channels. In the Tartarus processing scripts, this loss of digital resolution is referred to as the "GIS3 bitfix problem".

GIS Sky Images - GIS2 Detection Image - GIS2 sky image showing the regions used to determine whether the target was detected. The image is unbinned (14.7" per pixel). The source region comprises the area within the green circle on the image, excluding any areas within the dashed yellow lines. The background region comprises the area within the red circle on the image, excluding any areas within the dashed yellow lines.

GIS Sky Images - GIS Rebinned Image - Combine GIS2 and GI3 sky image, rebinned by a factor of 2 (29.4" per pixel). The green circle indicates the nominal position of the target.

GIS Sky Images - Veron Objects - Combined GIS2 and GIS3 sky image showing the locations and names of all objects from the 2001 Veron catalog that are in the field-of-view. The green circle shows either the nominal ("N") or centroided ("C") position of the target. The blue star shows the location of the object that is closest to the target position. The image is unbinned (14.7" per pixel) and smoothed with a Gaussian kernel of 2 pixels standard deviation.

Hidden unscreened SIS events files - For some observing sequences, the script t_cats hides certain unscreened SIS events files. The hiding of these files is primarily to excluded those data collected in an observing mode (e.g., SIS clocking mode) that does not match the mode in which the largest portion of the observation was conducted.

Light Curve (SIS0+SIS1) - Either Full (0.5-10 keV) or Full2 (0.6-10 keV) band light curve of the sum of the SIS0 and SIS1 counting rates. A bin size of 5760 s (roughly the ASCA orbital period) is preferentially used for the light curve shown on the web page. If this was not created then a 16 s binned light curve is shown.

Log file - Text file containing a log of the reduction and analysis of an observing sequence. The date and time at which the observing sequence was processed is indicated in the name of the log file, with the format YYYY.MM.DD.HH:MM.xxxxxxxx.seq, where the sequence number is given as xxxxxxxx.

Missing products - A list of files that should normally be included in the Tartarus products but were not present for a certain observing sequence.

N_H - Best-fitting Hydrogen column density. The absorption component has zero redshift.

NO FIT - The reduced chi-squared of the initial best-fitting model was greater than 15 so a detailed spectral fit was not carried out. The spectral image shows the initial best-fitting model. A fit might also not have been carried out if XSPEC was caught in an infinite loop.

Object name - Name of object as used by Tartarus.

Observing times (Elapsed) - Number of seconds between the start of the first good-time inteval and end of the last good-time interval for an observing sequence.

Observing times (Exposure) - Total number of seconds in all good-time intervals for an observing sequence.

Photon Index - Photon index from best-fitting power-law model, with or without absorption.

Prob. to Exceed - Probability of exceeding the chi-squared of the best-fitting model.

RA - Right ascension in equatorial co-ordinates (J2000).

Red. Chi² / DOF - Reduced chi-squared and degrees-of-freedom (DOF) of the best-fitting model.

Scaled Background Counts - Best estimate of the the number of background counts (Full or Full2 band) expected within the source region. This is the number of events observed within the background region of the detector image, multiplied by the ratio between the areas of the source and background regions. The background region comprises the area within the red square or circle, excluding any areas within the dashed yellow lines. For SIS0, only chip 1 is used, and for SIS1 only chip 3 is used. These chips are located at the lower-left in the detector images.

Sequence - The 8-digit sequence number designating an observation. The sequence numbers of AGN observations generally start with the digit 7. The term "observation ID", "observing sequence" or just "sequence" are used interchangably.

SIS0 - One of the two of solid-state imaging spectrometers. Referred to as detector number "0".

SIS0 Flux - Flux of the best-fitting model as determined using the SIS0 absolute flux calibration. The energy range used for the flux calculation is: 0.5-10 keV (Full), 0.5-2.0 keV (Soft) or 2.0-10.0 keV (Hard). Note that, for the Full and Soft bands, the spectral fitting extends down only to 0.6 keV.

SIS1 - One of the two of solid-state imaging spectrometers. Referred to as detector number "1".

SIS clocking mode - Number of chips (1,2,4) used per SIS detector for an observing sequence.

SIS data mode - Telemetry mode in which most data for an observing sequence were collected. BRIGHT2 mode data are converted from FAINT mode data, as are some BRIGHT mode data.

Source Region Counts - Total number of counts (Full or Full2 band) observed within the source region of the detector image. The source region comprises the area within the green circle on the images, excluding any areas within the dashed yellow lines. For SIS0, only chip 1 is used, and for SIS1 only chip 3 is used. These chips are located at the lower-left in the detector images.

Start date - Start date (UT) of an observing sequence, obtained from the earliest SIS0 (BRIGHT mode) unscreened file.

Start time - Start time (UT) of an observing sequence, obtained from the earliest SIS0 (BRIGHT mode) unscreened file.

Start MJD - Start date of an observing sequence, expressed as a Modified Julian Date, obtained from the earliest SIS0 (BRIGHT mode) unscreened file.

Unabsorbed Model - The spectral model does not included any component of absorption.

Upper limit - Upper limit (3 sigma) on the number of source counts in the detection region shown as the green circle in the GIS2 Detection Image.

Warnings - A list of warnings produced during the reduction and analysis of an observing sequence. The warnings serve mostly to indicate when a non-standard process was adopted for an observing sequence and are generally harmless.