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A2LCPOINT: Help

A2LCPOINT - HEAO 1 A2 Pointed Lightcurves


Overview

The A2 experiment was flown on the HEAO-1 satellite, from August, 1977 until January 1979.

The experiment consisted of six multi-layer, multi-anode collimated gas proportional counters. These were two LEDs (Low Energy Detectors), a MED (Medium Energy Detector), and three HEDs (High Energy Detectors). The first 6-months of mission were dedicated to an all-sky scan after which a pointing phase started.

This database table accesses the lightcurves available at HEASARC obtained from the A2 MED (small and large field of view) and HEDs (3 units, each with small and large field of view) detectors during the pointed phase.


Data Products

The MED and HEDs have two different field of views a small and a large, whose sizes are various combination of 3.0 X 1.5 degrees 3.0 x 3.0 degrees, 3.0 x 6.0 degrees (FWHM). The collimators were oriented so that the 3.0 degrees angular response was always perpendicular to the scan plane.

Lightcurves were extracted from the XRate database for a subset of positions included in the HEAO1 A2 pointing catalog (available as the A2POINT database at HEASARC). The A2POINT database contains the pointing positions of the A2 experiment when the primary instrument was either A2 or A1, located opposite to A2. The A2LCPOINT database includes only lightcurves for A2 pointings as primary instrument. Also, for 89 pointing where A2 was the primary instrument, no XRate are available (and therefore no lightcurves are available). For few known sources, data were extracted using the best known position for that source rather than the A2POINT position.

Each entry in the A2LCPOINT database has associated with it 4 lightcurves (in FITS format) extracted from the MED and HED3 small and large fields of view respectively. A single GIF file containing plots of the 4 lightcurves is also associated with each entry.

The lightcurves are background subtracted and collimator corrected, with an integration time of 5.12 seconds. Data were included only if the source position was within 15 % of the collimator response. The background applied was derived from the standard background values listed in the HEAO1-A2 data analysis system (LHEA June 1988) user guide.

Because of the large A2 FOV more than one source could be in the detector collimator. The database contains a flag "CONFUSED" to indicate that other sources may contribute to the total count rate and/or variability. The confusion flag was derived by cross correlating the A2 pointing position with source positions in the following catalogs: the HEAO 1 A3 MC LASS Catalog, HEAO 1 A2 Piccinotti Catalog, and the X-ray Binaries Catalog.


Parameters

Name
Nome of the 'object' as given in the pointed catalog (see A2point database).

RA
The Right Ascension of the pointing.

Dec
The Declination of the pointing.

LII
The galactic longitude of the pointing.

BII
The galactic latitude of the pointing.

Meds_Count_Rate
Lightcurve average count rate from the MED detector with the small field of view (MEDS). The count rate is background subtracted and obtained over the nominal MED energy range (1.5-20 keV). Note that for 11 entries the MEDS lightcurve is missing. In all these cases a values of -99.999 is assigned to the count rate (and error) for both MEDS and HD3S, even if the HD3S lightcurve exists.

Meds_Count_Rate_Error
Error on count rate from the MED-S detector.

Hd3s_Count_Rate
Lightcurve average count rate from the HED3 detector with the small field of view (HD3S). The count rate is background subtracted and obtained over the nominal HED3 energy range (2.5-60 keV).Note that for 11 entries the MEDS lightcurve is missing. In all these cases a values of -99.999 is assigned to the count rate (and error) for both MEDS and HD3S, even if the HD3S lightcurve exists.

Hd3s_Count_Rate_Error
Error on count rate from the HD3S detector.

Start_Date
File start time given as DD/MM/YY HH:MM:SS.

Stop_Date
File stop time given as DD/MM/YY HH:MM:SS.

Time
File start time given as SHF (for browse) or MJD for W3browse

End_Time
File stop time given as SHF (for browse) or MJD for W3browse

Exposure
The 'exposure' parameter (given in seconds) corresponds to the effective exposure on source.

Telapse
The 'Telapse' parameter (given in seconds) correspond to the time interval covered by the lightcurve (Stop - Start).

GIF_File
Root name for the GIF file showing the small field of view MED and HED3 lightcurves.

Meds_File
Root name for the MED-S lightcurve file obtained with the small field of view. This product is in FITS format.

Medl_File
Root name for the MED-L lightcurve file obtained with the small field of view. This product is in FITS format.

Hd3s_File
Root name for the HED3-S lightcurve file obtained with the small field of view. This product is in FITS format.

Hd3l_File
Root name for the HED3-S lightcurve file obtained with the small field of view. This product is in FITS format.

Confused
This parameter indicates if there was another (bright X-ray) source in the detector field of view. The parameter value is set to 1 if there is another source in the FOV otherwise is 0. The source confusion was derived by using positions that appear in the following catalogs: the HEAO 1 A3 MC LASS Catalog, HEAO 1 A2 Piccinotti Catalog, and the X-ray binaries catalog.

Quality
A crude quality flag was assigned to each lightcurve to flag possible data anomalies. These flags are preliminary and do not account for all the potential problems. Currently the parameter has two values: 10 if there are no obvious problem with the data, otherwise. Note that a quality flag of 10 is given also if there is another source in the FOV (see parameter CONFUSED).


Contact Person

Questions regarding the A2LCPOINT database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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