EXOHGLS - EXOSAT/CMA High Galactic Latitude Survey
The sample of sources in this cataogue has been selected from the CMA database, which it has been generated using a standard processing on the LE data. The source detection algorithm used a sliding cell method. The size of the search cell is such as to maximize the sensitivity across the field of view. For more information about the LE processing see the documentation in the CMA database.
The images are in linearized detector coordinates and de-blurred (to account for fluctuations of the pointing position which were quite small). The lightcurves are background subtracted and a time resolution of 2^n seconds, where n was optimized such that the average number of counts per bin is 0.3.
* log in to the `legacy.gsfc.nasa.gov` anonymous ftp area * go to `caldb/data/exosat/cma/cpf` * copy the `.rmf` file for the filter instrument combination you need * start XSPEC, then:model wabs po (or whatever your model is) fakeit none 10000 (or whatever your exposure is) flux 0.1 2.5
The `fakeit` and `flux` commands will give the flux and count rate for the model you have specified.* 7 = 3000 (thin) lexan
The EXOHGLS catalog name of the EXOSAT target/field.
The name of the EXOSAT target/field. There are many serendipitous sources in the EXOSAT LE images, and in some cases the name given here will reflect the original target name and not the actual source name.
Source order number
Source Classification. Type 'class' at the browse prompt for more info. Source not identified as the class filed set to 'uniden'.
The RA is the Right Ascension of the detected source.
The Dec is the Declination of the detected source.
The galactic longitude of the source.
The galactic latitude of the source.
Counting rate from the Al/P filter, if available from an observation of the same source made within one day. `AL count rate error` gives the error on the Al/P counting rate.
Al-Par Count Rate Error
Counting rate from the boron filter, if available (see the `AL count rate` description). `BO count rate error` gives the error on boron counting rate.
Boron Count Rate Error
For imaging instruments, the X pixels coordinate of the source in the detector is given by the parameter `X pixels`. The X value ranges between -1024 and 1023.
For imaging instruments, the Y pixels coordinate of the source in the detector is given by the parameter `Y pixels`. The Y value ranges between -1024 and 1023.
The file_image parameter contains the file name of the associated image.
Rates buffer indentifier (first letter)
Gives the time resolution of the associated data product lightcurve in seconds. The time resolution was 2^n seconds, where n was optimized such that the average number of counts per bin is 0.3.
The `time` of the observation refers to the start time. This is listed as yr.day, where yr is the last two digits of the year and day is the day of the year e.g., day 300 of 1984 is 84.300. All times are stored internally as a short history file key (SHF), which is the number of seconds before or after 1 January 1980 at 00:00 hrs UT. Times are accurate to the nearest second.
12-micron IRAS Flux
MJD key for buffer creation
The instrument paramater records which of the two telescope+detector combination, LE1+CMA1 or LE2+CMA2, were used in the observation to detect the source. The values are L1, for the combination LE1+CMA1, and L2, for the combination LE2+CMA2.
Some observation were carried out with an OBC program that sets a 'diamond' filter. This filter electronically screened out the outer part of the field of view. The resulting image, which is shaped as a diamond, covers only a fraction of the 2 X 2 deg. If the diamond filter wa s in used than the DIAMOND_FILTER paramater is set to 1 otherwise its value is 0.
ROSAT Id (spare)
The filter numbers are
* 6 = al/p
* 8 = boron
* 2 = PPL
* 3 = 4000 (thick) lexan
Distance from xpix=15, ypix=15
Observed Variance in TA1
expected variance in TA1
The `exposure` is the total on-source observation time in seconds. This includes all dead time effects, interruptions in coverage, etc.
Dead Time Correction
Counting rate from the ME detector during this observation (warning: this may not cover exactly the same time interval), it also covers the central field of view and so will include all sources seen by the LE. `ME count rate error` gives the error on the count rate.
ME Count Rate Error
25-micron IRAS Flux
60-micron IRAS Flux
The probability of the detection being due to random chance. Note, this is not scaled for the independent number of search attempts in an image.
Archival Tape Number Where Files Are Stored
Principal Investigator Code
Proposal Type (HLX)
ME Quality Flag
File name of the associated background lightcurve. One background lightcurve is associated to each image.
Redshift or HD Number of Counterpart
NH (10**19 cm-2) in the Galaxy
21 cm NH thru the galaxy H cm**-2 from Starke et al.
ME Count Rate in 3-6 keV Band
ME Count Rate Error in 3-6 keV Band
ME Count Rate in 1-3 keV Band
ME Count Rate Error in 1-3 keV Band
The 90-percent confidence uncertainty in arc seconds for the source position.
IPC Count Rate
IPC Count Rate Error
Radio Flux (mJy) at 5 GHz
detector deadtime correction factor
Flag for Radio Emission
Flag for Serendipitous Sources
Background Level (cts/s/sq.pixel)
The `count rate` and `count rate error` are the average counting rate (counts per sec) over the observation and its associated one sigma uncertainty.
Error on Count Rate
Observed Variance in TA2
expected variance in TA2
100-micron IRAS Flux
Date of Last Record Update
Quality flag for the LE. This is a number between 1 and 5, where 5 is excellent, and 1 means there may be a serious problem with the entry. A value of 3 means that the entry should be checked. For example, all boron filter entries have a qflag of 3, to warn of the problem with the psf for soft sources observed with this filter.
File name of the source lightcurve.
Visual Quality of Detection
Point Source Flag
Contact PersonQuestions regarding the EXOHGLS database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Monday, 08-Nov-2004 11:24:45 EST