GTI#

class gammapy.data.GTI(table, reference_time=None)[source]#

Bases: object

Good time intervals (GTI) Table.

Data format specification: GTI.

Note: at the moment dead-time and live-time is in the EVENTS header … the GTI header just deals with observation times.

Parameters

tableTable: GTI table.
reference_timeTime, optional: The reference time. Default is None. If None, use TIME_REF_DEFAULT.

Examples

Load GTIs for a H.E.S.S. event list:

>>> from gammapy.data import GTI
>>> gti = GTI.read('$GAMMAPY_DATA/hess-dl3-dr1//data/hess_dl3_dr1_obs_id_023523.fits.gz')
>>> print(gti)
GTI info:
- Number of GTIs: 1
- Duration: 1687.0000000000016 s
- Start: 123890826.00000001 s MET
- Start: 2004-12-04T22:08:10.184 (time standard: TT)
- Stop: 123892513.00000001 s MET
- Stop: 2004-12-04T22:36:17.184 (time standard: TT)

Load GTIs for a Fermi-LAT event list:

>>> gti = GTI.read("$GAMMAPY_DATA/fermi-3fhl-gc/fermi-3fhl-gc-events.fits.gz")
>>> print(gti)
GTI info:
- Number of GTIs: 39042
- Duration: 183139597.9032163 s
- Start: 239557417.49417615 s MET
- Start: 2008-08-04T15:44:41.678 (time standard: TT)
- Stop: 460249999.99999994 s MET
- Stop: 2015-08-02T23:14:24.184 (time standard: TT)

Attributes Summary

`met_start`	GTI start time difference with reference time in seconds, MET as a `Quantity`.
`met_stop`	GTI start time difference with reference time in seconds, MET as a `Quantity`.
`time_delta`	GTI durations in seconds as a `Quantity`.
`time_intervals`	List of time intervals.
`time_ref`	Time reference as a `Time` object.
`time_start`	GTI start times as a `Time` object.
`time_stop`	GTI end times as a `Time` object.
`time_sum`	Sum of GTIs in seconds as a `Quantity`.

Methods Summary

`copy`()	Deep copy of the `GIT` object.
`create`(start, stop[, reference_time])	Create a GTI table from start and stop times.
`delete_interval`(time_interval)	Select and crop GTIs in time interval.
`from_stack`(gtis, **kwargs)	Stack (concatenate) list of GTIs.
`from_table_hdu`(table_hdu[, format])	Read from table HDU.
`from_time_intervals`(time_intervals[, ...])	From list of time intervals.
`group_table`(time_intervals[, atol])	Compute the table with the info on the group to which belong each time interval.
`read`(filename[, hdu, format, checksum])	Read from FITS file.
`select_time`(time_interval)	Select and crop GTIs in time interval.
`stack`(other)	Stack with another GTI in place.
`to_table_hdu`([format])	Convert this GTI instance to a `astropy.io.fits.BinTableHDU`.
`union`([overlap_ok, merge_equal])	Union of overlapping time intervals.
`write`(filename, **kwargs)	Write to file.

Attributes Documentation

met_start#: GTI start time difference with reference time in seconds, MET as a Quantity.

met_stop#: GTI start time difference with reference time in seconds, MET as a Quantity.

time_delta#: GTI durations in seconds as a Quantity.

time_intervals#: List of time intervals.

time_ref#: Time reference as a Time object.

time_start#: GTI start times as a Time object.

time_stop#: GTI end times as a Time object.

time_sum#: Sum of GTIs in seconds as a Quantity.

Methods Documentation

copy()[source]#: Deep copy of the GIT object.

classmethod create(start, stop, reference_time=None)[source]#

Create a GTI table from start and stop times.

Parameters

startTime or Quantity: Start times, if a quantity then w.r.t. reference time.
stopTime or Quantity: Stop times, if a quantity then w.r.t. reference time.
reference_timeTime, optional: The reference time to use in GTI definition. Default is None. If None, use TIME_REF_DEFAULT.

delete_interval(time_interval)[source]#

Select and crop GTIs in time interval.

Parameters

time_interval[astropy.time.Time, astropy.time.Time]: Start and stop time for the selection.

Returns

gtiGTI: Copy of the GTI table with the bad time interval deleted.

classmethod from_stack(gtis, **kwargs)[source]#

Stack (concatenate) list of GTIs.

Calls vstack.

Parameters

gtislist of GTI: List of good time intervals to stack.
**kwargsdict, optional: Keywords passed on to vstack.

Returns

gtiGTI: Stacked good time intervals.

classmethod from_table_hdu(table_hdu, format='gadf')[source]#

Read from table HDU.

Parameters

table_hduBinTableHDU: table hdu.
format{“gadf”}: Input format, currently only “gadf” is supported. Default is “gadf”.

classmethod from_time_intervals(time_intervals, reference_time=None)[source]#

From list of time intervals.

Parameters

time_intervalslist of Time objects: Time intervals.
reference_timeTime, optional: Reference time to use in GTI definition. Default is None. If None, use TIME_REF_DEFAULT.

Returns

gtiGTI: GTI table.

group_table(time_intervals, atol='1e-6 s')[source]#

Compute the table with the info on the group to which belong each time interval.

The t_start and t_stop are stored in MJD from a scale in “utc”.

Parameters

time_intervalslist of astropy.time.Time: Start and stop time for each interval to compute the LC.
atolQuantity: Tolerance value for time comparison with different scale. Default is “1e-6 s”.

Returns

group_tableTable: Contains the grouping info.

classmethod read(filename, hdu='GTI', format='gadf', checksum=False)[source]#

Read from FITS file.

Parameters

filenamepathlib.Path or str: Filename
hdustr: hdu name. Default is “GTI”.
format: str: Input format, currently only “gadf” is supported. Default is “gadf”.
checksumbool: If True checks both DATASUM and CHECKSUM cards in the file headers. Default is False.

select_time(time_interval)[source]#

Select and crop GTIs in time interval.

Parameters

time_intervalastropy.time.Time: Start and stop time for the selection.

Returns

gtiGTI: Copy of the GTI table with selection applied.

stack(other)[source]#

Stack with another GTI in place.

This simply changes the time reference of the second GTI table and stack the two tables. No logic is applied to the intervals.

Parameters

otherGTI: GTI to stack to self.

to_table_hdu(format='gadf')[source]#

Convert this GTI instance to a astropy.io.fits.BinTableHDU.

Parameters

formatstr, optional: Output format, currently only “gadf” is supported. Default is “gadf”.

Returns

hduastropy.io.fits.BinTableHDU: GTI table converted to FITS representation.

union(overlap_ok=True, merge_equal=True)[source]#

Union of overlapping time intervals.

Returns a new GTI object.

Parameters

overlap_okbool, optional: Whether to raise an error when overlapping time bins are found. Default is True.
merge_equalbool; optional: Whether to merge touching time bins e.g. (1, 2) and (2, 3) will result in (1, 3). Default is True.

write(filename, **kwargs)[source]#

Write to file.

Parameters

filenamestr or Path: Filename.
**kwargsdict, optional: Keyword arguments passed to writeto.