SUBJECT: GRB 240918A: LIGO-Virgo-KAGRA GW targeted range

The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA
Collaboration report:

At the time of GRB 240918A (t0 = 2024-09-18 20:55:11.000), the H1, L1, and V1
interferometers were observing. The low-latency pipelines for compact binary
mergers [1-6] were operational at the time of the external event. No
gravitational-wave candidates were found in a window of (t0 - 5 s, t0 + 1 s).
We report in the following tables the targeted detectability range [7] for a
set of BNS and NSBH masses and inclination angles of the binary.

 | Masses (M_sun) | 0< iota < 45 deg | 0< iota < 90 deg |
 | -------------- | ---------------- | ---------------- |
 | 1.0 – 1.0      | 216.77 Mpc       | 92.00 Mpc        |
 | 1.4 – 1.4      | 287.14 Mpc       | 119.40 Mpc       |
 | 2.0 – 2.0      | 387.54 Mpc       | 160.33 Mpc       |

 | Masses (M_sun) | 0< iota < 45 deg | 0< iota < 90 deg |
 | -------------- | ---------------- | ---------------- |
 | 5.0 – 1.0      | 371.38 Mpc       | 154.83 Mpc       |
 | 10.0 – 1.4     | 561.86 Mpc       | 232.85 Mpc       |
 | 20.0 – 2.0     | 887.79 Mpc       | 365.74 Mpc       |

The targeted detectability range is defined as the distance where 90% of the
injected sources are recovered with a matched-filter SNR > 9. This SNR cut is
chosen to have the closest match, on average, between the targeted range
reported here and the PyGRB 90% exclusion distance.

Additional files, including the sky map of the targeted detectability range and
the BNS-NSBH detection efficiency curves, can be found here:
[10.5281/zenodo.22835797](https://doi.org/10.5281/zenodo.22835797)

An offline targeted analysis will be performed to search deeper for
gravitational-wave signals and determine exclusion limits.

 [1] Marx et al. PRD 111, 042010 (2025) doi:10.1103/PhysRevD.111.042010
 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018
 [3] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234
 [4] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a
 [5] Huang et al. (2025) arXiv 2511.04730
 [6] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023
 [7] Ronchini et al. A&A, forthcoming article (2026)
doi.org:10.1051/0004-6361/202661039