# Comment on "Tests of general relativity with GW170817"

## TL;DR

This paper challenges previous claims by showing that noise filtering effects in LIGO data can bias the interpretation of gravitational wave polarization, emphasizing the importance of proper data analysis methods.

## Contribution

It demonstrates that noise filtering can significantly affect polarization analysis, and that excluding affected frequency regions alters the conclusions about tensor versus vector polarization.

## Key findings

- Noise filtering reduces the measured signal at certain frequencies.
- Including all frequency regions can lead to incorrect polarization conclusions.
- Proper data analysis is crucial for accurate gravitational wave polarization testing.

## Abstract

In a recent paper "Tests of general relativity with GW170817" (arXiv:1811.00364 [gr-qc]) the authors claimed overwhelming evidence in favor of tensor gravitational wave (GW) polarization over vector by analyzing GW signals measured by the LIGO-Virgo network. Here we show that the measured LIGO-Livingston signal is substantially reduced at certain frequency intervals which can be attributed to noise filtering. We found that if these regions are excluded from the analysis then data are consistent with vector GW polarization and not with tensor. We show that if the signal accumulation method is applied over the entire detector bandwidth, including the regions in which the signal is depleted by noise subtraction, the result underestimates the LIGO-Livingston signal amplitude. That smaller amplitude then leads to an erroneous conclusion that favors tensor polarization over vector polarization for the GW.