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Time Series Table Format

Description of FITS tables intended for store of time series (light curves) or another time series data.

The table is created as output of munipack timeseries command.

The specification slightly follows SimpleTimeseries format (IMPORTANT: This link is intentionally dead due authors themselves. There is no widely accepted definition of a format for light curves and related affairs yet.) Generally, Munipack's format is a bit more simplified and restrictive.

File Structure

FITS file structure
HDUEXTNAMEDescription
0Dummy[†]
1TIMESERIESTime Series Table
2CATALOGUEObjects identification (coordinates)

[†] The first dummy extension contains keywords of identification HDUNAME, which is set mandatory to 'TIMESERIES', CREATURE is set to 'Munipack X.Y.Z' version and a link to this page as a comment.

Time Series Table

The main table which stores the time series.

Time Series Keywords
KeywordValueDefaultDescription
EXTNAMETIMESERIESTIMESERIESextension identifier
TIMETYPEJDJDType of TIME: JD (Julian Day), MJD (modified JD), HJD (heliocentric JD), phase φ[1]
TIMESYSUTCUTCTime system
TIMEREFGEOCENTRICReference time point
TIMESTMPMIDPOINTMIDPOINTtime stamp = MIDPOINT,BEGIN,END[2]
TIMEERRUncertainty in the time measurement[3]
TIMERESResolution in the time measurement[3]
FILTERFilter, spectral band-pass[4]
PHOTSYSPhotometry system[4]

[1] Definition of Julian (also other derived) days provides Julian day wiki page. The phase φ = {(t - t0)/P} is defined as fractional part ({x} = x - ⌊x⌋) of time difference HJD since the epoch t0 per period P.

[2] The time is labeled by timestamps (the elapsed time is T): at the begin t0 (BEGIN) up to finish t1 = t0 + T (END) time. The midpoint is computed as t0 + T/2.

[3] The keyword is optional. It is presented, if the value has been provided by user.

[4] Values are common spectral pass-band for all frames derived from FILTER and PHOTSYS keywords (for calibrated data).

Time Series Table
ColumnTypeDescription
TIME1DTime-like quantity[a]
EXPTIME1DIntegration time like quantity[b]
Qi1DQuantity for i-th object[c]
QEi1DStandard deviation of Q-i[c]

[a] Units of the time-like quantity in days (for H,M,JD). The phase has no units.

[b] The exposure time is directly copied from frames and units are (perhaps) seconds.

[c] Table can contain many physical quantities. For their meaning, see Photometry data table. The table can contains multiple columns of the quantities for all required objects.

Object Catalogue Table

This extension contains equatorial coordinates of objects of TIMESERIES extension.

Object Catalogue Keywords
KeywordValueDefaultDescription
EXTNAMECATALOGUECATALOGUEextension identifier
REFRAMEICRSReference celestial coordinate system
EPOCH2000Reference epoch for proper motion

Object catalogue Table
ColumnTypeDescriptionUnits
RAJ20001DRight Ascension[§]degrees
DEJ20001DDeclination[§]degrees

[§] Coordinates are referenced for epoch of the observation. Fast-moving objects can evince visible coordinate differences.

See Also

Time Series