...
(Ballet) We should add an uncertainty (1 sigma) to it.
(Digel) I agree.
Done.
4. Energy bands
| Anchor | ||||
|---|---|---|---|---|
|
(Ballet) I suggest we add the source count rates or fluxes (plus uncertainty) in several broad energy bands. This can be very useful when looking for unusual spectra (very different from a power law). I imagine the way to get that would be to run likelihood after event selection on energy in each energy band, then converting the prefactor value to a flux in that band for the spectral index of the source. Running likelihood directly on the image accumulated in that band would be another option, but this unfortunately requires an assumption on the spectral index as well (to build the PSF).
...
| No Format |
|---|
XTENSION = 'BINTABLE' / binary table extension BITPIX = 8 / 8-bit bytes NAXIS = 2 / 2-dimensional binary table PCOUNT = 0 / size of special data area GCOUNT = 1 / one data group (required keyword) TFIELDS = 3234 / number of fields in each row CHECKSUM = / checksum for entire HDU DATASUM = / checksum for data table TELESCOP = 'GLAST' / name of telescope generating data INSTRUME = 'LAT' / name of instrument generating data EQUINOX = 2000.0 / equinox for ra and dec RADECSYS = 'FK5' / world coord. system for this file (FK5 or FK4) EXTNAME = 'LAT_Point_Source_Catalog' / name of this binary table extension HDUCLASS = 'OGIP' / format conforms to OGIP standard HDUCLAS1 = 'EVENTS' / extension contains events HDUCLAS2 = 'ALL' / extension contains all events detected TSTART = / mission time of the start of the observation TSTOP = / mission time of the end of the observation TIMEUNIT = 'd' / units for the time related keywords TIMEZERO = 0.0 / clock correction TIMESYS = 'MJD' / type of time system that is used TIMEREF = 'LOCAL' / reference frame used for times DATE = / file creation date (YYYY-MM-DDThh:mm:ss UT) DATE-OBS = / start date and time of the observation (UTC) DATE-END = / end date and time of the observation (UTC) NDSKEYS = 0 / number of data subspace keywords in header HDUCLASS = 'OGIP ' / format conforms to OGIP standard HDUDOC = '?' / document describing the format HDUVERS = '1.0.0 ' / version of the format HDUCLAS1 = 'SRCLIST' / an OGIP standard class TTYPE1 = 'Source_Name' / e.g., 1GL J123456-012345 TFORM1 = '18A ' / character string TUNIT1 = 'none' / units of field TTYPE2 = 'RA' / right ascension of source TFORM2 = 'E' / floating point TUNIT2 = 'deg' / units of field TLMIN2 = 0.0 / minimum value TLMAX2 = 360.0 / maximum value TTYPE3 = 'DEC' / declination of source TFORM3 = 'E' / floating point TUNIT3 = 'deg' / units of field TLMIN3 = -90.0 / minimum value TLMAX3 = 90.0 / maximum value TTYPE4 = 'Conf_68_SemiMajor' / semimajor axis, 68% containment confidence region TFORM4 = 'E' / floating point TUNIT4 = 'deg' / units of field TLMIN4 = 0.0 / minimum value TLMAX4 = 360.0 / maximum value TTYPE5 = 'Conf_68_SemiMinor' / semiminor, axis, 68% containment confidence region TFORM5 = 'E' / floating point TUNIT5 = 'deg' / units of field TLMIN5 = 0.0 / minimum value TLMAX5 = 360.0 / maximum value TTYPE6 = 'Conf_68_PosAng' / position angle, 68% containment confidence region, E of N TFORM6 = 'E' / floating point TUNIT6 = 'deg' / units of field TLMIN6 = 0.0 / minimum value TLMAX6 = 360.0 / maximum value TTYPE7 = 'Conf_95_SemiMajor' / semimajor axis, 95% containment confidence region TFORM7 = 'E' / floating point TUNIT7 = 'deg' / units of field TLMIN7 = 0.0 / minimum value TLMAX7 = 360.0 / maximum value TTYPE8 = 'Conf_95_SemiMinor' / semiminor, axis, 95% containment confidence region TFORM8 = 'E' / floating point TUNIT8 = 'deg' / units of field TLMIN8 = 0.0 / minimum value TLMAX8 = 360.0 / maximum value TTYPE9 = 'Conf_95_PosAng' / position angle, 95% containment confidence region, E of N TFORM9 = 'E' / floating point TUNIT9 = 'deg' / units of field TLMIN9 = 0.0 / minimum value TLMAX9 = 360.0 / maximum value TTYPE10 = 'Flux100' / average photon flux >100 MeV TFORM10 = 'E' / floating point TUNIT10 = 'cm**(-2) s**(-1)' / units of field TLMIN10 = 0.0 / minimum value TLMAX10 = 1.0 / maximum value TTYPE11 = 'Unc_Flux100' / uncertainty (1-sigma) in average flux >100 MeV TFORM11 = 'E' / floating point TUNIT11 = 'cm**(-2) s**(-1)' / units of field TLMIN11 = 0.0 / minimum value TLMAX11 = 1.0 / maximum value TTYPE12 = 'Flux300' Flux30_100' / average photon flux >30030-100 MeV TFORM12 = 'E' / floating point TUNIT12 = 'cm**(-2) s**(-1)' / units of field TLMIN12 = 0.0 / minimum value TLMAX12 = 1.0 / maximum value TTYPE13 = 'Unc_Flux30_Flux300100' / uncertainty (1-sigma) in average flux >30030-100 MeV TFORM13 = 'E' / floating point TUNIT13 = 'cm**(-2) s**(-1)' / units of field TLMIN13 = 0.0 / minimum value TLMAX13 = 1.0 / maximum value TTYPE14 = 'Flux1000Flux100_300' / average photon flux >1000100-300 MeV TFORM14 = 'E' / floating point TUNIT14 = 'cm**(-2) s**(-1)' / units of field TLMIN14 = 0.0 / minimum value TLMAX14 = 1.0 / maximum value TTYPE15 = 'Unc_Flux1000Flux100_300' / uncertainty (1-sigma) in average flux >1000100-300 MeV TFORM15 = 'E' / floating point TUNIT15 = 'cm**(-2) s**(-1)' / units of field TLMIN15 = 0.0 / minimum value TLMAX15 = 1.0 / maximum value TTYPE16 = 'Flux3000Flux300_1000' / average photon flux >3000300-1000 MeV TFORM16 = 'E' / floating point TUNIT16 = 'cm**(-2) s**(-1)' / units of field TLMIN16 = 0.0 / minimum value TLMAX16 = 1.0 / maximum value TTYPE17 = 'Unc_Flux300_Flux30001000' / uncertainty (1-sigma) in average flux >1000300-1000 MeV TFORM17 = 'E' / floating point TUNIT17 = 'cm**(-2) s**(-1)' / units of field TLMIN17 = 0.0 / minimum value TLMAX17 = 1.0 / maximum value TTYPE18 = 'Spectral_Index'Flux3000' / average photon spectral index, >100flux >3000 MeV TFORM18 = 'E' / floating point TUNIT18 = 'nonecm**(-2) s**(-1)' / units / dimensionlessof field TLMIN18 = -100.0 / minimum value TLMAX18 = 101.0 / maximum value TTYPE19 = 'Unc_Spectral_IndexFlux3000' / uncertainty (1-sigma) in uncertainty,average photonflux spectral>3000 indexMeV TFORM19 = 'E' / floating point TUNIT19 = 'nonecm**(-2) s**(-1)' / units / dimensionlessof field TLMIN19 = 0.0 / minimum value TLMAX19 = 101.0 / maximum value TTYPE20 = 'VariabilitySpectral_Index' / fluxphoton variabilityspectral index (TBD), >100 MeV TFORM20 = 'E' / floating point TUNIT20 = 'none' / dimensionless TLMIN20 = ###-10.0 / minimum value (TBD) TLMAX20 = ###10.0 / maximum value (TBD) TTYPE21 TTYPE21 = ='SignifUnc_Spectral_Avg' Index' / detection significance (whole time interval)1-sigma uncertainty, photon spectral index TFORM21 = 'E' / floating point TUNIT21 = 'none' / dimensionless (sigmas) TLMIN21 = 0.0 / minimum value TLMAX21 = 110.0E90 / maximum value TTYPE22 = 'SignifVariability_PeakIndex' / flux variability / detection significance (peakindex (TBD) TFORM22 = 'E' / floating point TUNIT22 = 'none' / dimensionless (sigmas) TLMIN22 = 0.0### / minimum value (TBD) TLMAX22 = ### 1.0E9 / maximum value (TBD) TTYPE23 = 'FluxSignif_PeakAvg' / peakdetection fluxsignificance (>100 MeV) forwhole time interval above) TFORM23 = 'E' / floating point TUNIT23 = 'cm**(-2) s**(-1)'none' / dimensionless (sigmas) TLMIN23 = 0.0 / minimum value TLMAX23 = 1.0 0E9 / maximum value TTYPE24 = 'UncSignif_Peak_Flux' / detection uncertaintysignificance (1-sigma) in peak flux >100 MeVpeak) TFORM24 = 'E' / floating point TUNIT24 = 'cm**(-2) s**(-1)none' / units of field TLMIN24 = 0.0 / dimensionless (sigmas) TLMIN24 = 0.0 / minimum value TLMAX24 = 1.0 0E9 / maximum value TTYPE25 = 'TimeFlux_Peak' / center of peak flux (>100 MeV) for time interval of peak significanceabove TFORM25 = 'DE' / doublefloating precisionpoint TUNIT25 = 'd' / units of fieldcm**(-2) s**(-1)' TLMIN25 = 0.0 / minimum value TLMAX25 = 1.0D50 / maximum value TTYPE26 = 'Unc_Peak_IntervalFlux' / duration of time interval of peak significanceuncertainty (1-sigma) in peak flux >100 MeV TFORM26 = 'DE' / doublefloating precisionpoint TUNIT26 = 'cm**(-2) s**(-1)' / units of field TLMIN26 = 0.0 / minimum value TLMAX26 = 31.0D70 / maximum value TTYPE27 = 'FluxTime_History' Peak' / flux (>100 MeV) history (monthly)center of time interval of peak significance TFORM27 = '12ED' / floating point/ array, 12 months (number TBR)double precision TUNIT27 = 'cm**(-2) s**(-1)'d' / units of field TLMIN27 = 0.0 / minimum value TLMAX27 = 1.00D5 / maximum value TTYPE28 = 'FluxPeak_Unc_History'Interval' / duration fluxof uncertainty (1-sigma, >100 MeV) history TFORM23time interval of peak significance TFORM28 = '12ED' / floating point array, 12 months (number TBR) TUNIT23double precision TUNIT28 = 's' = 'cm**(-2) s**(-1)' / units of field TLMIN23TLMIN28 = 0.0 / minimum value TLMAX23TLMAX28 = 13.00D7 / maximum value TTYPE29 = 'HistFlux_Start' History' / startflux of(>100 timeMeV) intervals of flux historyhistory (monthly) TFORM29 = '12E' / floating point array, 12 months (number TBR) TUNIT29 = 'dcm**(-2) s**(-1)' / units of field TLMIN29 = 0.0 / minimum value TLMAX29 = 1.0D50 / maximum value TTYPE30 = 'IDFlux_Unc_CounterpartHistory' / sourceflux counterpartuncertainty (if any)1-sigma, >100 MeV) history TFORM30 = '20A12E' / characterfloating string TUNIT30point array, 12 months = 'none'(number TBR) TUNIT30 = 'cm**(-2) s**(-1)' / units of field TLMIN30 / dimensionless TTYPE31 = = 'Conf_Counterpart'0.0 / confidence of association of counterpart with source TFORM31 = 'I' / minimum value TLMAX30 = 1.0 / index, 1 = Figure of Merit, 2 =/ Correlatedmaximum variability TUNIT31 value TTYPE31 = 'noneHist_Start' / start of time intervals of /flux dimensionlesshistory TLMIN31TFORM31 = 0 '12E' / minimumfloating value TLMAX31point array, 12 months = 2 (number TBR) TUNIT31 = 'd' / units maximumof value field TTYPE32TLMIN31 = 'Flags'0.0 / flags (TBD) for catalog entry TFORM32 minimum value TLMAX31 = 1.0D5 = 'I' / maximum value TTYPE32 = 'ID_Counterpart' / integer TUNIT32source counterpart (if any) TFORM32 = 'none20A' / character dimensionless END |
...
string
TUNIT32 = 'none' / dimensionless
TTYPE33 = 'Conf_Counterpart' / confidence of association of counterpart with source
TFORM33 = 'I' / index, 1 = Figure of Merit, 2 = Correlated variability
TUNIT33 = 'none' / dimensionless
TLMIN33 = 0 / minimum value
TLMAX33 = 2 / maximum value
TTYPE34 = 'Flags' / flags (TBD) for catalog entry
TFORM34 = 'I' / integer
TUNIT34 = 'none' / dimensionless
END
|
| Anchor | ||||
|---|---|---|---|---|
|
Comments on the draft of 26 October 2005
...
(Luigi Foschini)
Keywords to add:
EXTREL: release number of the template for the FITS header, to take into account for future developments and changes in the header.
CREATOR: the name and version of the executable that generated the FITS file.
CONFIGUR: name and version of the software system under which the executable run (e.g. SAE v X.x).
DATE: date of the creation of the FITS file.
TIMEREF: time reference frame (LOCAL, SOLAR SYSTEM, etc...).
TIMEUNIT: I suggest to change to days (JD), so that to use MJDREF as TZERO and it is possible to avoid huge numbers; TSTART and TSTOP should be updated accordingly.
VERSION: version of the catalog.
RADECSYS: FK5 default; stellar reference frame.
EQUINOX: 2000.0 default; coordinate system equinox.
I would add also a new column "NOTES" (character string) where to place some comments, like, for example, other names of the sources (e.g. the corresponding name in the 3rd EGRET catalog, etc...).
...
(Seth Digel, 30 December 2005)
I have updated the draft header above to take into account Luigi's comments and to finally include the fluxes for several energy bands. I also reformatted it to make it more like an actual template FITS header.
The updated draft includes DATE, TIMEREF, RADECSYS, and EQUINOX.
I omitted EXTREL because I believe the same information would be conveyed by HDUVERS.
CREATOR and VERSION are assumed to be in the main header for the file, which is not shown. To the extent possible we will have a common format for the primary headers of all our FITS data products; I intend to post a template for comment. CONFIGUR is assumed to be in the main header as well, with the name SOFTWARE
TIMEUNIT is changed to days, TIMESYS to 'MJD' and MJDREF is omitted. These changes, I think, permit the dates in the flux histories to be represented as MJD values. I think that we want these times in MJD rather than seconds of MET (as I had originally proposed) or as days with respect to January 1, 2001 (as Luigi proposed). Also I think that the description is correctly expressed in column 26 so that the duration of the interval used for the peak flux evaluation is in days. A detailed description of representing time in Chandra FITS files is available here (see section 2). I need to study it some more.
NOTES is omitted; the proposed use is good - especially for providing other names for identified sources - but how to make a NOTES column conveniently searchable or even figuring out how large a field to reserve is not clear. We'll have to revisit this.
Also, regarding flux histories, I am assuming that in columns 27 & 28, for intervals during which a source was not detected we'll have its flux entry as 0 and its flux uncertainty should be interpreted as a (2 sigma?) upper limit.
Regarding fluxes for multiple energy bands (see item 4 above), I have written the header so that each band has two columns, one for flux and one for its uncertainty. It could be written more compactly using arrays, so that only two columns total would be required to store the fluxes and flux uncertainties for all of the bands. But as Jean pointed out, having separate columns may be a convenience for searching. That said, the column names that I have used, e.g., FLUX30_100 and UNC_FLUX30_100 for the 30-100 MeV range, are fairly ugly and the UNC_FLUX* column names, although valid, are not unique within the first 8 characters as the HEASARC at least strongly prefers. Do you have any better ideas for naming the columns?
I've left the flux history and peak flux entries specified as corresponding to the range >100 MeV. I'd prefer to leave it that way for the purposes of the Catalog - the same energy range for every source and every time range
...
Comments on the draft of 26 October 2005
(Luigi Foschini)
Keywords to add:
EXTREL: release number of the template for the FITS header, to take into account for future developments and changes in the header.
CREATOR: the name and version of the executable that generated the FITS file.
CONFIGUR: name and version of the software system under which the executable run (e.g. SAE v X.x).
DATE: date of the creation of the FITS file.
TIMEREF: time reference frame (LOCAL, SOLAR SYSTEM, etc...).
TIMEUNIT: I suggest to change to days (JD), so that to use MJDREF as TZERO and it is possible to avoid huge numbers; TSTART and TSTOP should be updated accordingly.
VERSION: version of the catalog.
RADECSYS: FK5 default; stellar reference frame.
EQUINOX: 2000.0 default; coordinate system equinox.
I would add also a new column "NOTES" (character string) where to place some comments, like, for example, other names of the sources (e.g. the corresponding name in the 3rd EGRET catalog, etc...).
(Seth Digel, 30 December 2005)
I have updated the draft header above to take into account Luigi's comments. I also reformatted it to make it more like an actual template FITS header.
The updated draft includes DATE, TIMEREF, RADECSYS, and EQUINOX.
I omitted EXTREL because I believe the same information would be conveyed by HDUVERS.
CREATOR and VERSION are assumed to be in the main header for the file, which is not shown. To the extent possible we will have a common format for the primary headers of all our FITS data products; I intend to post a template for comment. CONFIGUR is assumed to be in the main header as well, with the name SOFTWARE
TIMEUNIT is changed to days, TIMESYS to 'MJD' and MJDREF is omitted. These changes, I think, permit the dates in the flux histories to be represented as MJD values. I think that we want these times in MJD rather than seconds of MET (as I had originally proposed) or as days with respect to January 1, 2001 (as Luigi proposed). Also I think that the description is correctly expressed in column 26 so that the duration of the interval used for the peak flux evaluation is in days. A detailed description of representing time in Chandra FITS files is available here (see section 2). I need to study it some more.
NOTES is omitted; the proposed use is good - especially for providing other names for identified sources - but how to make a NOTES column conveniently searchable or even figuring out how large a field to reserve is not clear. We'll have to revisit this.
Also, regarding flux histories, I am assuming that in columns 27 & 28, for intervals during which a source was not detected we'll have its flux entry as 0 and its flux uncertainty should be interpreted as a (2 sigma?) upper limit.
...