Calculating SNR from GWTC reported values and PSD

Data Analysis
1

Dear colleague,

I attempted to calculate SNRs using the reported values in GWTC for primary masses, secondary masses, redshifts and using PSDs obtained from GWTC-3: Compact Binary Coalescences Observed by LIGO and Virgo During the Second Part of the Third Observing Run — Parameter estimation data release to then compare them to the reported SNRs in GWTC. I calculate the SNR using equation 19 from https://arxiv.org/pdf/2409.00179

I focus on events with SNR larger than 8 and primary mass larger than 4.

The attached figure shows the ratio between the reported SNR value the SNR value I calculate for each event with SNR larger than 8 and primary mass larger than 4, the figure shows a tendency to underestimate the value of the SNR. I suspect there might be a problem with my use of the PSDs (I use the ‘C01:IMRPhenomXPHM’ PSD with default frequency cutoff values). I might be missing some technical aspect to the SNR calculation. Do you see anything wrong with my approach. Your help would be much appreciated.

Please let me know if further clarification is needed.

Best regards,

Mehdi El Bouhaddouti

ratio_real_over_sim_snr_m1_v2
ratio_real_over_sim_snr_m1_v23300×1952 106 KB

2

Thank you for your question!

I’m not sure where the issue is, but I can provide some suggestions:

  • I’m noticing that the expression in equation 19 does not involve the antenna factor for the instrument. Any detected signal has its SNR projected onto the detector via an antenna factor. That might be a source of scatter in your plot.

  • If you’d like to test your expression, you might compare some values with the SNR as calcuated by gwpy or pycbc. You could calculate some optimal SNRs or add a simulated waveform to noise for a controlled experiment. This would be a way to side-step the antenna factor issue and check for a systematic in your expression.

Good luck!

3

Thank you for your answer!