---
title: "Einstein@Home"
chunk: 3/6
source: "https://en.wikipedia.org/wiki/Einstein@Home"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:24:16.361890+00:00"
instance: "kb-cron"
---

An Einstein@Home study on how to optimally use the limited computing power for directed searches (where prior information on the target object such as the sky position is available) was published on 31 January 2018. It describes the design of searches for continuous gravitational waves over a wide frequency range from three supernova remnants (Vela Jr, Cassiopeia A, and G347.3). The results from the directed Einstein@Home search for continuous gravitational waves from the central objects of the supernova remnants Vela Jr., Cassiopeia A, and G347.3 was published on 29 July 2019. It covered a frequency range from 20 Hertz to 1500 Hertz and used data from LIGO's first observing run O1. No signal was found and the most stringent upper limit at the time of publication were set, improving earlier results by a factor of two for all three targets. A follow-up of the Einstein@Home search for continuous gravitational waves from the central objects of the supernova remnants Vela Jr., Cassiopeia A, and G347.3 was published on 29 June 2020. It investigated the most promising 10,000 candidates from the previous search and followed them up in two stretches of data from LIGO's second observing run (O2). A single candidate associated with G347.3 remained as a possible signal after the follow-up, but was not conclusively confirmed based on gravitational-wave data. Archival X-ray data were searched for pulsations at the putative rotation frequency of the neutron star and its integer multiples. No signal was found. It is expected that data from LIGO's third observing run (O3) will suffice to shed light on the nature of this potential candidate. On 8 March 2021 results from an Einstein@Home all-sky search for continuous gravitational waves in LIGO O2 data were published. It used an eight-stage follow-up process and covered a frequency range from 20 Hertz to 585 Hertz and reached the highest sensitivity for any all-sky survey below 500 Hertz. Six candidates were found after all follow-up stages. They are consistent with and caused by validation hardware injections in the LIGO instruments. No other signal was found. The most stringent upper limit (90% confidence) was set in a 0.5 Hertz band at 163 Hertz at a gravitational-wave strain amplitude of 1.3×10−25. The results begin to probe neutron star astrophysics and population properties. They exclude neutron stars with rotation frequencies above 200 Hertz with ellipticities larger than 10−7 (which are predicted by some models of neutron star crusts) closer than 100 parsec. Results from a dedicated Einstein@Home search for continuous gravitational waves from the central object of the supernova remnant G347.3 was published on 5 August 2021. In the analysed frequency range between 20 Hertz and 400 Hertz no signal was found. The derived upper limits correspond to ellipticities of less than 10−6 for most of the frequency band. In the most sensitive frequency band at 166 Hertz the upper limit (90% confidence) on gravitational-wave strain is 7.0×10−26. In July 2023, the results of an all-sky search for continuous gravitational waves in the public LIGO O3 data were published. The search was the most sensitive at that time for gravitational waves with frequencies between 2o Hertz and 800 Hertz and with spin-downs of up to −2.6×10−9 Hz s−1. No astrophysical gravitational-wave signal was identified, and all candidate signals could be attributed to artificial signals injected into the LIGO data for validation purposes. The results exclude the existence of isolated neutron stars spinning at rotational frequencies of more than 200 Hertz with ellipticities larger than 5×10−8 closer than 100 parsec.