# Sub-threshold binary neutron star search in Advanced LIGO's first observing run

## TL;DR

This paper reports a sensitive search for gravitational waves from binary neutron star inspirals during LIGO's first observing run, identifying sub-threshold candidates that could include real events, and provides data for multi-messenger follow-up.

## Contribution

It presents the most sensitive survey within a specific mass range during LIGO's first run, including single-detector data, and offers a candidate list for multi-messenger astronomy.

## Key findings

- No definitive gravitational wave signals detected.
- Candidate list contains ~1 potential real event based on expected merger rates.
- Analysis includes single-detector data, increasing sensitivity.

## Abstract

We present a search for gravitational waves from double neutron star binaries inspirals in Advanced LIGO's first observing run. The search considers a narrow range of binary chirp masses motivated by the population of known double neutron star binaries in the nearby universe. This search differs from previously published results by providing the most sensitive published survey of neutron stars in Advanced LIGO's first observing run within this narrow mass range and including times when only one of the two LIGO detectors was in operation in the analysis. The search was sensitive to binary neutron star inspirals to an average distance of ~85 Mpc over 93.2 days. We do not identify any unambiguous gravitational wave signals in our sample of 103 sub-threshold candidates with false-alarm-rates of less than one per day. However, given the expected binary neutron star merger rate of R = 100 - 4000 Gpc^(-3) yr^(-1), we expect O(1) gravitational wave events within our candidate list. This suggests the possibility that one or more of these candidates is in fact a binary neutron star merger. Although the contamination fraction in our candidate list is ~99%, it might be possible to correlate these events with other messengers to identify a potential multi-messenger signal. We provide an online candidate list with the times and sky locations for all events in order to enable multi-messenger searches.