GTI

class gammapy.data.GTI(table, reference_time=None)

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()

Deep copy of the GIT object.

classmethod create(start, stop, reference_time=None)

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)

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)

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')

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)

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')

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)

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)

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)

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')

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)

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)

Write to file.

Parameters:

filenamestr or Path

Filename.

**kwargsdict, optional

Keyword arguments passed to writeto.