Analysing a GW event

For a brief overview of the analysis and results on a simulated signal, see Overview.

Here, we analyze a real GW event using the simple_pe_gracedb and simple_pe_pipe executables. For concreteness, we use events from ER15: S230518h and S230522a (we include the second example as it was observed in only on detector).

simple_pe_pipe requires command line arguments to run. Out of convenience, these command line arguments can be provided from a configuration file, and obtained by running simple_pe_gracedb.

Example: S230518h

This is a two detector event with the two LIGO Observatories, H1 and L1 operational at the time.

To set up the analysis, run simple_pe_gracedb with the following arguments

simple_pe_gracedb --sid S230518h --outdir ./outdir

This will download all required data from GraceDB and generate the following configuration file:

[pesummary]
trigger_time =
channels = {H1:GDS-CALIB_STRAIN_CLEAN,L1:GDS-CALIB_STRAIN_CLEAN}
outdir = ./outdir
f_low = 20.0
f_high = 2048.0
trigger_parameters = {}
approximant = IMRPhenomXPHM
psd = {H1:./outdir/gracedb/H1_psd.txt,L1:./outdir/gracedb/L1_psd.txt}
minimum_data_length = 256
snr_threshold =
peak_finder = grid
convert_samples = True
accounting_group =
accounting_group_user =

Note

Certain information has been removed for confidentiality

We see that the minimum data length is set to 256s. This is must be set to be long enough to handle any type of signal without truncation of the waveform. In optimizing the SNR, the code explores the parameter space and may generate BNS waveforms. If the event you are running is definitely a BBH merger, then you may find that reducing the minimum data length speeds up the analysis.

To launch this analysis, simply run:

simple_pe_pipe ./outdir/config.ini

This will produce the simple-pe results for the event.

Example: S230522a

This is a one detector event with the L1 Observatory reported as being operational at the time of the event.

To set up the analysis, run simple_pe_gracedb with the following arguments

simple_pe_gracedb --sid S230522a  --outdir ./outdir

As before, this will download all required data from GraceDB and generate the following configuration file:

[pesummary]
trigger_time =
channels = {L1:GDS-CALIB_STRAIN_CLEAN}
outdir = ./outdir
f_low = 20.0
f_high = 2048.0
trigger_parameters = {}
approximant = IMRPhenomXPHM
psd = {L1:./outdir/gracedb/L1_psd.txt}
minimum_data_length = 256
snr_threshold =
peak_finder = grid
convert_samples = True
accounting_group =
accounting_group_user =

As before, this job can be launched by running:

simple_pe_pipe ./outdir/config.ini