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A4SPECTRA: Help

A4SPECTRA - HEAO 1 A4 Spectra


Overview

The UCSD/MIT Hard X-Ray and Low-Energy Gamma-Ray Instrument, A4, was flown on the HEAO 1 satellite, between August 1977 until January 1979. The experiment consisted of a collection of collimated sodium iodide scintillators, two of which the Low Energy detectors (LED, LED-3 and LED-6), were optimized for the lower energy part of the hard X-ray range between 13 to 180 keV. The first 6-months of mission were dedicated to an all-sky scan after which a pointing phase started. In pointing mode the A4-LED instrument look axis was kept in a 1 deg dead band centered on the target position. Instead in the "ping-pong" mode the look axis was regularly alternated with a secondary target a few degrees away, usually for background determination. This database table accesses the spectra (and associated files) obtained from the A4-LED detectors in the ping-pong mode.

Data Products

For each database entry, source and background spectra, together with the appropriate response matrices are available for the A4 LED-3 and and A4 LED-6 detectors. These products are all in FITS format and were created at University of California (San Diego) as part of an ADP grant (PI Duane Gruber). A plot viewing the LED-3 and LED-6 background subtracted spectra is also available in GIF format. This was created at HEASARC using the spectral software package xspec.

Note on Data Products

Few spectra give negative c/s after background subtraction, not consistent with one sigma error.

The background spectrum obtained for the LED-3 detector for the position ra=300.0 and dec=39.7 (spectral file a4_d3_2000p397_a.bkg) shows strong evidence for a point source which most likely coincide with Cyg X-1. On the contray the pointing spectrum (a4_d3_2000p397_a.pha) probably is consistent with a blank sky.

The LED-3 and LED-6 source spectra for the position ra=268.5 and dec=-23.4 (spectral file a4_d3_1754m234_a.pha and a4_d6_1754m234_a.pha) correspond to a pointing of Jupiter, but in the background spectra (a4_d3_1754m234_a.bkg, a4_d6_1754m234_a.bkg) is contaminated by a fairly strong source to GX 5-1.


Parameters

Alt_Name
Contains a source name derived from cross-correlation with the following catalogs : xrbcat, a2pic, a4, a3

BII
The galactic latitude of the source.

Class
Source Classification. The class paramater was compiled using the following catalogs:xrbcat, a2pic, a4, a3.

D3_Count_Rate
Count rate from the spectrum obtained with the LED-3 detector. The count rate is background subtrated and calculated in the channel range 7-30 (corresponding 14-80 kev).

D3_Count_Rate_Error
Error on count rate from the LED-3 detector.

D3_Exposure
Exposure given in seconds for the LED-3 detector.

D3_Filename
Root name for the LED-3 source and background spectra. These products are in FITS format.

D3_Respfile
Root name for the LED-3 response file. This product is in FITS format.

D6_Count_Rate
Count rate from the spectrum obtained with the LED-6 detector. The count rate is background subtrated and calculated in the channel range 7-30 (corresponding 14-80 kev).

D6_Count_Rate_Error
Error on count rate from the LED-6 detector.

D6_Exposure
Exposure given in seconds for the LED-6 detector.

D6_Filename
Root name for the LED-6 source and background spectra. These products are in FITS format.

D6_Respfile
Root name for the LED-6 response file. This product is in FITS format.

Dec
The Dec is the Declination of the detected source.

GIF_File
Root name for the spectral plot of the LED-3 and LED-6 spectra. This product is in GIF format.

LII
The galactic longitude of the source.

Name
The paramater 'name' contains the value stored in the keyword OBJECT of the fits file.

RA
The RA is the Right Ascension of the detected source.

Start_Date
Date of Observation Start given as DD/MM/YY hh:mm:ss (string).

Start_Time
Start time of the observation.

Stop_Date
Date of Observation Stop given as DD/MM/YY hh:mm:ss (string).

Stop_Time
Stop time of the observation.


Contact Person

Questions regarding the A4SPECTRA 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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