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

the reference time If None, use TIME_REF_DEFAULT. Default is None

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: 1687.0 s
- Start: 123890826.0 s MET
- Start: 2004-12-04T22:08:10.184 (time standard: TT)
- Stop: 123892513.0 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: 460250000.0 s MET
- Stop: 2015-08-02T23:14:24.184 (time standard: TT)

Attributes Summary

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

Methods Summary

copy()
create(start, stop[, reference_time])	Creates a GTI table from start and stop times.
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])	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 sec, MET (Quantity).

met_stop

GTI start time difference with reference time in sec, MET (Quantity).

time_delta

GTI durations in seconds (Quantity).

time_intervals

List of time intervals

time_ref

Time reference (Time).

time_start

GTI start times (Time).

time_stop

GTI end times (Time).

time_sum

Sum of GTIs in seconds (Quantity).

Methods Documentation

copy()

classmethod create(start, stop, reference_time=None)

Creates 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

the reference time to use in GTI definition. If None, use TIME_REF_DEFAULT. Default is None

classmethod from_stack(gtis, **kwargs)

Stack (concatenate) list of GTIs.

Calls vstack.

Parameters

gtislist of GTI

List of good time intervals to stack

**kwargsdict

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: str

Input format, currently only “gadf” is supported

classmethod from_time_intervals(time_intervals, reference_time=None)

From list of time intervals

Parameters

time_intervalslist of Time objects

Time intervals

reference_timeTime

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 1e-6 sec.

Returns

group_tableTable

Contains the grouping info.

classmethod read(filename, hdu='GTI', format='gadf')

Read from FITS file.

Parameters

filenamepathlib.Path, str

Filename

hdustr

hdu name. Default GTI.

format: str

Input format, currently only “gadf” is supported

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

format: str

Output format, currently only “gadf” is supported

Returns

hdu: astropy.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

Whether to raise an error when overlapping time bins are found.

merge_equalbool

Whether to merge touching time bins e.g. (1, 2) and (2, 3) will result in (1, 3).

write(filename, **kwargs)

Write to file.

Parameters

filenamestr or Path

File name to write to.