GINGALAC - Ginga Source Lightcurves & Spectra

Overview

The GINGALAC database table contains a summary of the contents of the Ginga pointed observations. This table has been produced from the raw Ginga LAC First Reduction Files (FRFs) and contains information of the individual pointings in addition to FITS spectra and light curves, HDS and FITS data cubes and the plots produced during the pipeline processing. These products can be used with either the Ginga data analysis software or the XANADU software suite.

References

Angelini, L., Pence, W., Tennant, A.F., 1994, The Proposed Timing FITS File Format for High Energy Astrophysics Data. NASA/GSFC

Arnaud, K.A., George, I.M., Tennant, A.F., 1995, The OGIP Spectral File Format. NASA/GSFC

Clearly, M.N., Heiles, C., Haslam, C.G.T., 1979, Astr. Astrophys. Suppl., 36, 95

Hayashida, K., et al., 1989, PASJ, 41, 373

Heiles, C., Clearly, M.N., 1979, Australian J. Phys. Ap. Suppl., 47, 1

Kondo, H., 1988, MSc thesis, University of Tokyo

Makino, F., et al., 1987, Astrophys. Letters Commun., 25, 223

Marshall, F.J., Clark, G.W., 1984, ApJ, 287, 633

Murakami, T., et al., 1989, PASJ, 41, 405

Nandra, K., 1991, PhD these, University of Leicester

Nandra, K., Pounds, K.A., 1994, MNRAS, 268, 405

Stark, A.A., Heiles, C., Bally, J., Linke, R., 1984, Bell Laboratories privately distributed tape

Stella, L., Angelini, L., 1993, XRONOS: A Timing Analysis Software Package User's Guide. NASA/GSFC

Tennant, A.F., 1991, The QDP/PLT User's Guide. NASA Technical Memorandum 4301

Tsunemi, H., Kitamoto, S., Manabe, M., Miyamoto, S., Yamashita, K., PASJ, 41, 391

Turner, M.J.L., et al., 1989, PASJ, 41, 345

Williams, O.R., et al., 1992, ApJ, 389, 157

Provenance

This archive (database and all the associated products) is a copy of the GINGA LAC data products held at the Leicester Data Archive Service (http://ledas-www.star.le.ac.uk). It was delivered to the HEASARC in 1999 as part of an archive exchange between the data centers. The original version was updated in October 2008, when the positions (which had been created assuming the wrong equinox) were corrected; in addition, the values of the nh parameter were corrected.

Description

Ginga was the third Japanese X-ray astronomy satellite. It was launched into a low Earth orbit on 5th February 1987 and re-entered the atmosphere on 1st November 1991. The scientific payload consisted of the Large Area Counter (LAC; Turner et al. 1989), the All-Sky Monitor (ASM; Tsunemi et al. 1989) and the Gamma-ray Burst Detector (GBD; Murakami et al. 1989). A full description of the satellite is given in Makino et al. (1987). During its lifetime Ginga performed over 1000 observations of approximately 350 different targets, covering all then known classes of cosmic X-ray sources.

The LAC experiment, sensitive to X-rays with energy 1.5-37 keV, consisted of an array of eight proportional counters with a total effective area of approximately 4000 cm² and an energy resolution of 18% at 6 keV, scaling as E^-0.5 throughout the full energy range. In each counter the anode structure was of a multi-layer and multi-cell design which provided both gain uniformity and low internal background through the use of anti-coincidence. The high voltage supply was normally operated at 1830V, but was reduced occasionally to 1745V to achieve a larger energy range. Steel collimators restricted the field of view to 1.1 x 2.0 degrees (FWHM); the top and bottom 15mm were coated with silver paint to prevent contamination through iron, nickel and chrome fluorescent lines. The fluorescent line of silver at 22.1 keV can be visible at high energy but it is well away from lines of astrophysical importance and can be used for calibration.

The origin and behavior of the LAC background is described in Hayashida et al. (1989). The main sources of background include the internal component generated after passage through the Earth's radiation belts, in particular the South Atlantic Anomaly (SAA), the high- and low-energy particles in the Earth's magnetosphere, and the diffuse Cosmic X-ray Background (CXB). The first two sources generate a background which is a strong function of time and energy. Summed over the top- and mid-layer electrodes as well as over the full energy range (1.5-37 keV), this varies between 50 and 100 counts/second. The CXB contributes approximately 18 counts/second to the background, which varies as a function of position in the sky but is constant in time.

Accessing HEASARC Data

The data products belonging to an observation may be extracted using the Browse interface. Data can also be retrieved from https://heasarc.gsfc.nasa.gov/FTP/ginga/. A description of the data products is available in the https://heasarc.gsfc.nasa.gov/FTP/ginga/doc/ directory.

Accessing LEDAS Data

The products belonging to an observation may be extracted using the ARNIE interface to the LEDAS database (http://ledas-www.star.le.ac.uk/arnie/).

Spectral FITS

Spectra have been extracted from the cleaned, background subtracted and attitude corrected data cubes, and are integrated over the entire observational interval. The top- and mid-layers are treated separately within the database. Where the background subtracted LAC 2-10 keV count rate exceeds 2 counts/second, both layers are simultaneously fit to simple absorbed power-law and thermal bremsstrahlung models. Plots of the best-fit models are available within the database as are the results of the fits with their errors. In addition, the top-layer spectra are fitted to power-law and thermal bremsstrahlung models with and without a narrow (intrinsic width much less than the energy resolution of 1 keV) Gaussian emission line at 6-7 keV. As for joint fits, plots of the best-fit models and results of the fits are available in the database. If the presence of an emission line is significant at the 95% level (determined by an F-test), then the best-fit emission line parameters are also written to the database.

The spectral files within the database can be used to make more detailed fit to the data than has been performed in the pipeline. The format of the spectral files follows the OGIP FITS conventions (Arnaud, George & Tennant 1995) and these files can be used within the XSPEC spectral fitting package, which is part of the XANADU suite of software.

All errors are 90% confidence for one interesting parameter.

Background Estimation

Background subtraction is performed whenever there are blank-sky data available and the background subtracted data cube is made available within the database. Occasionally, we rejected data acquired during periods when the angle between the satellite pointing direction and the Sun was less than 90 degrees or the high voltage supply was reduced to 1745V.

The background is estimated by modeling the known contributions to the count rates and periodicities observed in them. Both the local and universal methods described in Hayashida et al. (1989) and Williams et al. (1992) are used (the background subtraction method is written to each record within the database table). The background count rate, C(E,t), dependent on both energy, E, and time, t, is given as

                C(E,t) =C₁(E) + sum C_n(E,t),

where

                C_n(E,t) = P_n(t) x F_n(E).

The first term C₁(E) represents the CXB contribution, which is constant in time, but varies across the sky due to fluctuations in the CXB. The remaining, time-variable instrumental components are characterized by their spectra F_n(E) and associated HK parameters P_n (e.g. COR, SUD). The spectral form, F_n(E), was determined by fitting data from background observations as described below.

In modeling the component of the background due to radioactive decays, we calculated a time counter, accumulated with an exponential decay factor, after each passage through the SAA. In practice, we used up to four time counters with exponential decay timescales corresponding to half-lives of 8 hours, 41 minutes and 20 minutes (see Hayashida et al. 1989 and Nandra 1991). The number of decays required in the model was reduced during the latter half of the mission to only one component, because of the decay of the Ginga orbit caused the LAC to be further shielded from the Earth's radiation belts. The Universal model uses all background observations within a contemporary three to four month period to model systematic trends in the particle levels, and hence to estimate the background level at the time of the source observation. A specific time counter is required to account for the 37-day precessional period of Ginga. The local method was used exclusively during the first six months and last three months of operation of Ginga as the gradual rise and fall of the background made the universal method unreliable.

The uncertainty in the background subtraction is limited by source confusion and systematic errors rather than statistical uncertainties in the data. The limiting sensitivity for source detection was chosen to be 2.1 counts/second, equivalent to a 3 sigma detection (Hayashida et al. 1989). All observations whose background subtracted 2-10 keV top-layer count rate exceeded 2.1 counts/second were removed from the background modeling pipeline. This can be achieved only after background subtraction, and so the whole process is an iterative procedure. The LAC mid-layer is insensitive to X-ray photons below 6 keV (Turner et al. 1989). Therefore, all observations were rejected from the background modeling pipeline if the background subtracted mid-layer count rate below 6 keV was significantly above or below zero. In addition, observations were rejected from the background modeling pipeline if the background subtracted spectra and light curves (3-10 keV band) showed trends with energy and/or time.

Light Curves

Light curves have been extracted, form the same data cubes as have the spectral data (see Spectral FITS); in the energy bands 2-6, 6-7, 7-17 and 2-17 keV. These bands cover the soft X-ray emission, the iron K line emission, the hard X-ray continuum and the full energy band. There are light curves for both the top- and mid-layers. In addition, the intrinsic variability (total variance minus statistical noise) is given in the databases as

        N / (N-1) ((sum x_i² / N) - mu²) - sum sigma_i²,

where x_i is the count rate for bin i, mu is the mean count rate during the observation and sigma_i² is the variance for bin i. There are light curves for both the top- and mid-layers.

The format of the files follows OGIP FITS conventions (Angelini, Pence & Tennant 1994) and they can be used within the XRONOS timing analysis package (Stella & Angelini 1993), which is part of the XANADU suite of software.

Data Selection Within SORTAC

The program SORTAC allows the selection of data in FRFs, producing data cubes (time, spectral and detector resolution) as output. Initially the data were selected from the FRFs, with full spectral resolution and a time resolution of 16 seconds (for higher time resolution studies, and different modes, it will be necessary to return to the FRFs held within the GINGAFRF database). Limits were placed on certain HK parameters during the extraction of data, with the LAC count rate above 24 keV (known as Surplus above Upper Discriminator or SUD), the energy that a cosmic-ray requires to penetrate the magnetosphere (Cut-Off Rigidity or COR) and the solid state electron monitor count rate (SOL2) all restricted to avoid periods of high particle background (these limits are listed below). Contamination from the bright Earth was prevented by restricting the angle between the satellite pointing direction and the Earth's horizon (YELEV) to greater than 6 degrees. Occasionally it was necessary to restrict the data with tighter constraints. The constraints actually used are stored for each observation in the database. In addition, DELTXZ (the angle between the satellite pointing direction and the nominal Ginga field of view) has been restricted to 0.4 degrees. This removes periods when the collimator transmission was less than 60 and 70% for the X- and Z-directions respectively. For solar angles (angle between the satellite pointing direction and the Sun) less than 90 degrees, solar X-rays can penetrate the LAC via the collimator when the satellite is in sunlight. These data were excluded from the database by restricting the observational intervals to those in the Earth's shadow. Whilst this may lead to a large reduction in the useful length of an observation, it does ensure that the data products are free of solar contamination. The minimum acceptable exposure time for any observation was 100 seconds.

              ---------------------------------
              HK Parameter       Data selection
              ----------------------------------
                  SUD           < 10 counts/sec
                  COR             10-20 GeV/c
                  SOL2          < 15
                  PI/SUD        < 3 sigma
                  LAC/LAC       < 5 sigma
                  LAC/SUD       not used
              ----------------------------------

Quality Flag

The quality of the data products is primarily determined by the quality of the background subtraction. This is indicated by the QFLAG field which has been filled after visual inspection of all the products. QFLAG has a range of 0 to 5 (no background subtraction to excellent; see table below). Observations with a QFLAG less than 3 are usually not of sufficient quality for spectral and/or timing analysis and the experienced user is recommended to re-background subtract the cleaned data cubes for spectral and/or timing analysis.

          ------------------------------------------
           Qflag                 Description
          ------------------------------------------
             0            No background subtraction
             1                 Unusable
             2                   Poor
             3                 Acceptable
             4                   Good
             5                 Excellent
          ------------------------------------------

Completeness

The GINGALAC database contains all the LAC target observations except those taken in modes other than MPC1 or where the pointing direction is particularly unstable.

Gain

To provide an indication of the gain, for each observation, the 10-35 keV pulse height spectra, which include the collimator silver line, from the top- and mid-layers (all detectors combined to provide good signal-to-noise) were fitted with a model consisting of a second order polynomial plus Gaussian emission line. The best-fit energy of the Gaussian is given in the database table and is accurate to approximately 0.5 keV. In addition, four plots were produced during the extraction of data. These show the pulse height spectra from 20 to 35 keV for the top- and mid-layers and for each detector in use (two detectors per plot). The plots can be used within QDP (Tennant 1991), which is part of the XANADU suite of software, to verify that the silver line is at the expected energy of 22.1 keV for individual layers. Individual plots may be missing if the detectors were excluded during the pipeline processing (e.g. because of electronic noise on detectors 5 & 6).

Data Selection Post SORTAC

The data were "cleaned" as described in Nandra & Pounds (1994) to remove periods of poor quality data. The process consists of the following stages. First, the SUD and V1 electrode (LAC anode wires not illuminated via the collimator; PI_MONI) rates were compared, and data from times when they were greater than 3 standard deviations from the best-fit linear relationship were removed from further analysis. Second, the LAC count rates in adjacent spectral channels were compared, and points lying greater than 5 standard deviations from the best-fit linear relationship were also removed (the relatively poor spectral resolution of the LAC ensures that this does not remove valid data). Plots are available in the database showing the SUD rate versus the PI_MONI rate. These plots are produced after data rejection so that the user can verify that the cleaning algorithm has successfully removed poor quality data.

A number of additional plots were produced during the pipeline data selection and cleaning process. First, a plot of SUD rate versus time allows the user to evaluate the background level during an observation (the total background scales with the SUD rate). The user may wish to extract data from periods of low background (i.e. low SUD rate). Second, a plot of YELEV versus the LAC top-layer count rate from the pulse height channel 4 is available. There will be no correlation between these two parameters if the data are unaffected by solar X-rays scattered into the Ginga field of view by the Earth's atmosphere (see Data Selection Within SORTAC).

Attitude Correction

The two-dimensional off-axis response of the collimator has been derived from slew data of the Crab Nebula (Kondo 1988; Turner et al. 1989). From this response, a post facto energy-independent vignetting correction has been calculated and applied to the background subtracted data cubes (these provide a third data cube). Spectra and light curves were extracted from these attitude corrected data cubes for periods when the transmission exceeded 70%. This corresponds to an offset of 0.3 degrees and 0.4 degrees for the X- and Z-directions respectively. However, the inner surfaces of the collimators were found to be reflective in the X-direction, amounting to a few percent below 6 keV for an offset of 0.3 degrees from the collimator axis (Turner et al. 1989), which is not corrected for.

Both attitude and non-attitude corrected data cubes contain information regarding the satellite pointing position and roll angle as a function of time, thus allowing the user to calculate the appropriate correction for extended and confused sources.

In addition, two plots are available which show the LAC top- and mid-layer count rates versus a number of HK parameters. In particular, the plots show attitude corrected LAC count rate versus SUD, SOL2, DELTXZ and the transmission. LAC count rate versus SUD and SOL2 can be used to verify that there are no count rate enhancements on the Ginga orbital period (SUD) or due to hard (SUD) and soft (SOL2) particles. The LAC count rate versus DELTXZ can be used to verify that the attitude solution has removed count rate variations due to pointing instability (e.g. during slews at the beginning and end of observations). Satellite pointings away from the source along the X-axis can cause enhancements due to collimator reflection.

Pipeline Processing

The pipeline has been run on all MPC1 mode pointed observations; in this mode data have full spectral resolution (48 channels), at the expense of a lower time resolution (16 seconds at low bit-rate). Over 80% of all Ginga observations were made in MPC1 mode. The pipeline is described below. All observations have been subject to expert quality assessment, and a simple quality flag is added to each observation record (see Quality).

Parameters

Name
Designation of the observed object.

RA
Nominal Right Ascension of the Ginga field of view.

Dec
Nominal Declination of the Ginga field of view.

LII
Nominal Galactic Longitude of the Ginga field of view.

BII
Nominal Galactic Latitude of the Ginga field of view.

Beta
Angle between the satellite pointing direction and the Sun at the time of observation (degrees).

NH
Galactic hydrogen column density in the direction of the Ginga field of view. These values were calculated using an interpolation from data taken from Marshall and Clark (1984). This covers the entire sky and uses various 21-cm surveys for its source (Stark et al. 1984; Clearly, Heiles & Haslam 1979; Heiles & Clearly 1979).

Time
The start time of the observation.

End_Time
The end time of the observation.

Duration
The duration of the observation (i.e. End_Time minus Start_Time; in days).

Exposure
Total live time on source (seconds).

Count_Rate
Mean 2-10 keV count rate after background subtraction (counts/second). Counts are taken from the top-layer only.

Count_Rate_Error
Error for mean 2-10 keV count rate after background subtraction (counts/second). Counts are taken from the top-layer only.

HR
Hardness ratio [(H-M)/(H+M), where H and M are the 10-17 keV and 6-10 keV count rates respectively]. The HR_Error is the one sigma uncertainty in the hardness ratio.

HR_Error
Error for hardness ratio [(H-M)/(H+M), where H and M are the 10-17 keV and 6-10 keV count rates respectively]. The HR_Error is the one sigma uncertainty in the hardness ratio.

SR
Softness ratio [(S-M)/(S+M), where S and M are the 2-6 keV and 6-10 keV count rates respectively]. The SR_Error is the one sigma uncertainty in the softness ratio.

SR_Error
Error for softness ratio [(S-M)/(S+M), where S and M are the 2-6 keV and 6-10 keV count rates respectively]. The SR_Error is the one sigma uncertainty in the softness ratio.

Filespec
String identifying the set of data products associated with an observation.

Root
String identifying the set of data products associated with an observation.

Respfile
String identifying the response matrices associated with an observation.

Qflag
Quality flag.

Mode
Mode of observation (i.e. MPC1).

Time_Res
Increment for temporal data (seconds).

Sol_Max
Maximum accepted rate of the solid state electron monitor (counts/second).

Cor_Min
Minimum accepted value for the cut-off rigidity (GeV/c).

Cor_Max
Maximum accepted value for the cut-off rigidity (GeV/c).

Hv_Min001
Minimum accepted high voltage level for detector 1.

Hv_Min002
Minimum accepted high voltage level for detector 2.

Hv_Min003
Minimum accepted high voltage level for detector 3.

Hv_Min004
Minimum accepted high voltage level for detector 4.

Hv_Min005
Minimum accepted high voltage level for detector 5.

Hv_Min006
Minimum accepted high voltage level for detector 6.

Hv_Min007
Minimum accepted high voltage level for detector 7.

Hv_Min008
Minimum accepted high voltage level for detector 8.

Hv_Max001
Maximum accepted high voltage level for detector 1.

Hv_Max002
Maximum accepted high voltage level for detector 2.

Hv_Max003
Maximum accepted high voltage level for detector 3.

Hv_Max004
Maximum accepted high voltage level for detector 4.

Hv_Max005
Maximum accepted high voltage level for detector 5.

Hv_Max006
Maximum accepted high voltage level for detector 6.

Hv_Max007
Maximum accepted high voltage level for detector 7.

Hv_Max008
Maximum accepted high voltage level for detector 8.

Yelev_Min
Minimum accepted angle between the satellite pointing direction and the Earth's horizon (degrees).

Yelev_Max
Maximum accepted angle between the satellite pointing direction and the Earth's horizon (degrees).

SUD_Min
Minimum accepted SUD count rate (counts/second).

SUD_Max
Maximum accepted SUD count rate (counts/second).

Htvolts001
Observed high voltage level for detector 1.

Htvolts002
Observed high voltage level for detector 2.

Htvolts003
Observed high voltage level for detector 3.

Htvolts004
Observed high voltage level for detector 4.

Htvolts005
Observed high voltage level for detector 5.

Htvolts006
Observed high voltage level for detector 6.

Htvolts007
Observed high voltage level for detector 7.

Htvolts008
Observed high voltage level for detector 8.

Srce_Mask
Detectors in which data have been accumulated (0 = off; 1 = on; i.e. 11110011 indicates that the data has been accumulated from detectors 1-4 and 7-8).

The detectors in which data have been accumulated (0 = off; 1 = on; i.e. 11110011 indicates that the data has been accumulated from detectors 1-4 and 7-8).

Cln_Sigma001
Data lying this number of standard deviations from the observed SUD/PI_MONI correlation were rejected (a value of 0.0 indicates that no attempt was made to exclude data using this correlation).

Data lying this number of standard deviations from the observed SUD/PI_MONI correlation were rejected (a value of 0.0 indicates that no attempt was made to exclude data using this correlation).

Cln_Sigma002
Data lying this number of standard deviations from the observed SUD/LAC correlation were rejected (a value of 0.0 indicates that no attempt was made to exclude data using this correlation).

Data lying this number of standard deviations from the observed SUD/LAC correlation were rejected (a value of 0.0 indicates that no attempt was made to exclude data using this correlation).

Cln_Sigma003
Data lying this number of standard deviations from the observed LAC/LAC correlation were rejected (a value of 0.0 indicates that no attempt was made to exclude data using this correlation).

Data lying this number of standard deviations from the observed LAC/LAC correlation were rejected (a value of 0.0 indicates that no attempt was made to exclude data using this correlation).

Bgd_Ndecay
Number of decays used in modeling the LAC background.

Number of decays used in modeling the LAC background.

Bgd_Decay001
The e-folding timescale of the first decay.

The e-folding timescale of the 1st decay.

Bgd_Decay002
The e-folding timescale of the second decay.

The e-folding timescale of the 2nd decay.

Bgd_Decay003
The e-folding timescale of the third decay.

The e-folding timescale of the 3rd decay.

Bgd_Decay004
The e-folding timescale of the fourth decay.

The e-folding timescale of the 4th decay.

Bgd_Version
Method of background subtraction used (i.e. local or universal method).

Method of background subtraction used (i.e. local or universal method).

PI_Moni_Min
Minimum accepted PI_MONI rate (counts/second).

PI_Moni_Max
Maximum accepted PI_MONI rate (counts/second).

Sunshine_Min
Minimum accepted value of the sunshine flag (0: shadow, 1: sunshine).

Sunshine_Max
Maximum accepted value of the sunshine flag (0: shadow, 1: sunshine).

Transmission_Min
Minimum accepted transmission (percentage).

Transmission_Max
Maximum accepted transmission (percentage).

Sud
Mean SUD count rate (counts/second). SUD_Error is the one sigma uncertainty in the mean SUD count rate (counts/second).

SUD_Error
Error for mean SUD count rate (counts/second). SUD_Error is the one sigma uncertainty in the mean SUD count rate (counts/second).

PI_Moni
Mean PI_MONI count rate (counts/second). PI_MONI_Error is the one sigma uncertainty in the PI_MONI count rate (counts/second).

PI_Moni_Error
Error for mean PI_MONI count rate (counts/second). PI_MONI_Error is the one sigma uncertainty in the PI_MONI count rate (counts/second).

Cor
Mean cut-off rigidity (GeV/c).

Yelevation
Mean angle between the satellite pointing direction and the Earth's horizon (degrees).

Sol2
Mean rate of the solid state electron monitor (counts/second).

Sunshine
Mean value of the sunshine flag (0: shadow, 1: sunshine).

Point_RA
Mean observed Right Ascension in J2000 decimal degrees.

Point_Dec
Mean observed Declination in J2000 decimal degrees.

Roll
Mean roll angle during the observation (degrees).

Anti
Mean anti-coincidence rate (counts/second).

Yaxis
Mean pointing flag (0: Sky, 1: Dark Earth, 2: Bright Earth).

Alt
Mean satellite altitude (kilometers).

Deltx
Mean angle between the observed pointing direction and the nominal pointing direction (DELTXZ) projected onto the X (short) axis of the collimator (degrees).

Deltz
Mean angle between the observed pointing direction and the nominal pointing direction (DELTXZ) projected onto the Z (long) axis of the collimator (degrees).

Deltxz
Mean angle between the observed pointing position and nominal pointing direction field of view (degrees).

Transmission
Mean collimator transmission (percentage).

Gbd_Sc
Mean Gamma-ray burst detector scintillation counter rate (counts/second).

Gbd_Pc
Mean Gamma-ray burst detector proportional counter rate (counts/second).

Ag_Energy001
Best-fit energy of the silver emission line in the nth raw spectrum (n = 1 for the top-layer; n = 2 for the mid-layer).

Ag_Energy002
Best-fit energy of the silver emission line in the nth raw spectrum (n = 1 for the top-layer; n = 2 for the mid-layer).

PL_Alpha
Energy index of the best-fit power-law.

PL_Alpha_Lo
Lower uncertainty on the energy index.

PL_Alpha_Hi
Upper uncertainty on the energy index.

PL_Norm
Power-law normalization (photons/second/cm/cm/keV at 1 keV).

PL_Norm_Lo
Lower uncertainty on the power-law normalization.

PL_Norm_Hi
Upper uncertainty on the power-law normalization.

PL_NH
Column density (H-atoms/cm²).

PL_NH_Lo
Lower uncertainty on the column density.

PL_NH_Hi
Upper uncertainty on the column density.

PL_Line_Present
Presence of an iron emission line (Boolean). True/False if the reduction in chi-square is significant/insignificant at the 95% level (determined by an F-test).

PL_Len
Best-fit line energy if line present (keV).

PL_Len_Lo
Lower uncertainty on line energy.

PL_Len_Hi
Upper uncertainty on line energy.

PL_EW
Equivalent width of emission line (eV).

PL_Ew_Lo
Lower uncertainty on line equivalent width.

PL_Ew_Hi
Upper uncertainty on line equivalent width.

PL_Redchi
Reduced chi squared of best-fit model (chi²/degrees of freedom).

PL_Nfree
Number of degrees of freedom.

PL_Flux
Absorbed 2-10 keV flux (erg/cm²/s).

Br_kT
Temperature of best-fit thermal Bremsstrahlung model (keV).

Br_kT_Lo
Lower uncertainty on temperature.

Br_kT_Hi
Upper uncertainty on temperature.

Br_Norm
Bremsstrahlung normalization (equal to 3.01*10^-15*S*T^-0.5 / (4*pi*D²), where S = int Ne² dV is emission measure in cm^-3 and D is the distance to the source in cm).

Br_Norm_Lo
Lower uncertainty on the Bremsstrahlung normalization.

Br_Norm_Hi
Upper uncertainty on the Bremsstrahlung normalization.

Br_NH
Column density (H-atoms/cm²).

Br_NH_Lo
Lower uncertainty on the column density.

Br_NH_Hi
Upper uncertainty on the column density.

Br_Line_Present
Presence of an iron emission line (Boolean). True/False if the reduction in chi-square is significant/insignificant at the 95% level (determined by an F-test).

Br_Len
Best-fit line energy if line present (keV).

Br_Len_Lo
Lower uncertainty on line energy.

Br_Len_Hi
Upper uncertainty on line energy.

Br_EW
Equivalent width of emission line (eV).

Br_Ew_Lo
Lower uncertainty on line equivalent width.

Br_Ew_Hi
Upper uncertainty on line equivalent width.

Br_Redchi
Reduced chi squared of best-fit model (chi²/degrees of freedom).

Br_Nfree
Number of degrees of freedom.

Br_Flux
Absorbed 2-10 keV flux (erg/cm²/s).

Int_Var_0206_001
Intrinsic 2-6 keV variance for the nth light curve (n = 1 for the top-layer; n = 2 for the mid-layer).

Int_Var_0206_002
Intrinsic 2-6 keV variance for the nth light curve (n = 1 for the top-layer; n = 2 for the mid-layer).

Int_Var_0607_001
Intrinsic 6-7 keV variance for the nth light curve (n = 1 for the top-layer; n = 2 for the mid-layer).

Int_Var_0607_002
Intrinsic 6-7 keV variance for the nth light curve (n = 1 for the top-layer; n = 2 for the mid-layer).

Int_Var_0717_001
Intrinsic 7-17 keV variance for the nth light curve (n = 1 for the top-layer; n = 2 for the mid-layer).

Int_Var_0717_002
Intrinsic 7-17 keV variance for the nth light curve (n = 1 for the top-layer; n = 2 for the mid-layer).

Int_Var_0217_001
Intrinsic 2-17 keV variance for the nth light curve (n = 1 for the top-layer; n = 2 for the mid-layer).

Int_Var_0217_002
Intrinsic 2-17 keV variance for the nth light curve (n = 1 for the top-layer; n = 2 for the mid-layer).

Contact Person

Questions regarding the GINGALAC database table can be addressed to the HEASARC Help Desk.

Questions specifically about the contents of the GINGALAC database table may also be addressed to ledas-help@star.le.ac.uk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:28:01 EDT