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SSS - Einstein SSS Spectra and Lightcurves |
HEASARC Archive |
The total background due to all non-source contributions is 0.28 ct/s above 0.5 keV and 0.19 ct/s above 1 keV. Background is not measured simultaneously, and must be estimated from data accumulated over source-free exposures.
A time-dependent build-up of ice (water) on the detector surface occurred because of cryopumping of ambient outgassing material onto the 100 K detector. It was periodically defrosted by heating to 220 K at the beginning of a series of three days of observations. Each defrost reduced the total amount of ice that returned, such that after 9 months the ice covering was almost gone. The ice covering is parameterized by an ice parameter that varies from a low value of 0.05 to a high early on of 4.58. A model has been developed that predicts the ice parameter as a function of time, and is used to obtain the correct response matrix for any given observation. The uncertainty in this ice parameter varies throughout the operational lifetime, and is greatest at the beginning. More information on the ice modeling procedure can be obtained in Arnaud, Szymkowiak, and White (1989, HEAO Newsletter, Vol. 1, No. 2) and Christian, Swank, and White (1992, Legacy: the HEASARC Newsletter, Vol. 1, No. 1).
Further information about the SSS calibration and the associated uncertainties can be obtained from VIMAT, by typing `vimat help`.
The cryogen keeping the SSS at its operating temperature of 100 K ran out, as expected, in October 1979, and no more observations were possible.
There is at least one spectrum per SSS observation of each target. If the observations covered an interval that extends over more than one (UT) day, then there is a spectrum accumulated for each day. The spectra are not background-subtracted. Detector response matrices and background spectra are made using the VIMAT program, or from within BROWSE using the XSPEC command.
Lightcurves: There is a background-subtracted 81.92 s time resolution light curve in the 1.0-4.0 keV band covering the time interval of each spectrum.
Associated Products: The Einstein monitor proportional counter, MPC, operated in the 1-15 keV band, with eight pulse height channels. It was a mechanically collimated detector with a full width half maximum field of view of 45 arc minutes.
There is one MPC spectrum accumulated to match each SSS spectrum (with the small number of exceptions noted above where there are no matching MPC observations). The spectra are not background-subtracted. Background spectra and the detector response matrix (the latter is considered to be valid for the entire mission) can be extracted using the VIMAT program.
There are also background-subtracted 40.96 s time resolution light curves in the 1.0-15.0 keV band covering the time interval of each spectrum.
Notice that, due to the differing instrumental observing constraints and particle background thresholds, the SSS and MPC data products are only quasi-simultaneous. The start and stop times referred to in the parameters description refer specifically to the SSS observations.
Associated_File_Lightcur
Associated lightcurve names
Associated_File_Response
Associated file response
Associated_File_Spectrum
The root name of the files containing the MPC spectrum (.pha).
BII
The galactic latitude and of the pointing.
Class
The HEASARC BROWSE Class of the target. (This classification scheme is
described in detail in the HEASARC document `Available Databases`).
Comments
Comments
Count_Rate
The count rate in the 0.6 to 4.5 keV band. Note that the count rate
is affected by the ice accumulating on the detector, and will change
from observation to observation because of this. Two other count rates
are available
* `min count rate` - minimum count rate during the observation * `Max count rate` - maximum count rate during the observation.
Count_Rate_Error
Count Rate Error
Deadtime
Deadtime
Dec
The Declination of the pointing.
Delta_Ice
The change in ice parameter across the spectral accumulation time.
End_Time
The end time of the SSS observation in the same format.
Exposure_Time
The total on source time, corrected for dead time.
File_Lcurve
The root name of the files containing the SSS lightcurves (.rbf).
File_Name
The root name of the files containing the SSS spectrum (.pha) and lightcurves
(.rbf).
File_Spectrum
The root name of the files containing the SSS spectrum (.pha).
Flux
flux (0.5-4.0 keV) (Note: All values are zero as populated.)
Ice_Start
The value of the ice parameter at the start of the spectral
accumulation.
Ice_Stop
The value of the ice parameter at the end of the spectral accumulation.
If there is a large jump in the ice parameter (10 percent or more) then the
ice build-up occurred rapidly, and the spectral fits at less than 1 keV
may not be reliable.
Jcg
good c
Lalcurve
Length of assoc lightcurves
Laspectra
Length of assoc spectra
LII
The galactic longitude of the pointing.
Llcurve
Length of lightcurves
Lspectra
Length of spectra
Max_Count_Rate
Maximum count rate
Max_Count_Rate_Error
Error on maximum count rate
Min_Count_Rate
Minimum count rate
Min_Count_Rate_Error
Error on minimum count rate
Nalcurve
Number of assoc lightcurves
Name
The name of the nominal SSS target. We have tried to select the most commonly
used name in all cases, but this of course is somewhat a matter of opinion.
(Note that the names contain embedded blanks, e.g., Cyg X-1)
Naspectra
Number of assoc spectra
Nlcurve
Number of lightcurves
Nspectra
Number of spectra
RA
The Right Ascension of the pointing.
Refs
References
Sequence_Number
This is the Einstein Sequence Number for the observation.
Tchi2
The `tchi2` parameter is a chi**2 test to a constant source intensity.
Time
The start time of the SSS observation specified in the format "Year.Day".
Type
This is a classification made by Jean Swank and Damien Christian as to the
nature of the source. The following types have been defined:
'bes' for X-ray binary with Be star primary: e.g., Gam Cas. 'blk' for X-ray binary with black hole primary: e.g., Cyg X-1. 'cluster' for cluster of galaxies: e.g., A 2029. 'cvs' for cataclysmic variable: e.g., AM Her. 'gal' for galaxy or quasar: e.g., 3C273. 'lmxb' for low-mass X-ray binary: e.g., Cyg X-2. 'pulsar' for pulsar: e.g., Cen X-3. 'rscvn' for RS CVn active binary system: e.g., AR Lac. 'snr' for supernova remnant: e.g., sn 1006. 'star' for miscellaneous varieties of galactic stars not belonging to the other stellar categories: e.g., tau Sco. 'mispt' for observations made at incorrect co-ordinates (i.e., mispoints).
Year
The year of the observation.