Editing Einstein@Home (section)

== Gravitational-wave data analysis and results ==
[[File:Einstein@Home.png|alt=responsive graphics|thumb|Einstein@Home screensaver]]
Einstein@Home has carried out many analysis runs using data from the LIGO instruments. Since its first search run in 2005, the sensitivity of the LIGO detectors has been improved in a series of steps and upgrades. This is continuing with the current Advanced LIGO detectors. At the same time, Einstein@Home search algorithms have also improved. Together these have increased the search sensitivity by several orders of magnitude.

Einstein@Home's first analysis<ref name="EaHS3">{{cite web | url = http://albert.phys.uwm.edu/PartialS3Results/ | title = First report on the S3 analysis | access-date = September 11, 2005 | archive-date = December 21, 2011 | archive-url = https://web.archive.org/web/20111221063125/http://albert.phys.uwm.edu/PartialS3Results/ | url-status = live }}</ref> used data from the "third science run" (S3) of LIGO. Processing of the S3 data set was conducted between 22 February 2005 and 2 August 2005. This analysis employed 60 segments from the LIGO Hanford 4-km detector, totaling ten hours of data each. Each 10-hour segment was analyzed for CW signals by the volunteers' computers using a [[Matched filter|matched-filtering]] technique. When all matched-filtering results were returned, the results from different segments were then combined in a "post-processing step" on Einstein@Home servers via a coincidence scheme to further enhance search sensitivity. Results were published on the Einstein@Home webpages.<ref name="EaHS3Final">{{cite web |url=http://albert.phys.uwm.edu/FinalS3Results/ |title=Final report on the S3 analysis |access-date=March 28, 2007 |archive-date=November 21, 2011 |archive-url=https://web.archive.org/web/20111121030146/http://albert.phys.uwm.edu/FinalS3Results/ |url-status=live }}</ref>

Work on the S4 data set (LIGO's fourth science run) was started via interlacing with the S3 calculations and finished in July 2006. This analysis used 10 segments of 30 hours each from the LIGO Hanford 4-km detector and 7 segments of 30 hours each from the LIGO Livingston 4-km detector. Besides the S4 data being more sensitive, a more sensitive coincidence combination scheme was also applied in the post-processing. The results of this search have led to the first scientific publication of Einstein@Home in ''[[Physical Review D]]''.<ref name="EaHS4">{{cite journal | journal = [[Physical Review D]] | volume = 79 | issue = 2 | page = 022001 |doi=10.1103/PhysRevD.79.022001 | title = Einstein@Home search for periodic gravitational waves in LIGO S4 data|bibcode = 2009PhRvD..79b2001A |arxiv = 0804.1747 | year = 2009 | last1 = Abbott | first1 = B. | s2cid = 16542573 | display-authors = etal}}</ref>

Einstein@Home gained considerable attention in the international volunteer computing community when an optimized application for the S4 data set analysis was developed and released in March 2006 by project volunteer Akos Fekete, a Hungarian programmer.<ref name="User profile">{{cite web | url = https://einsteinathome.org/account/141782 | title = Profile: Akos Fekete | access-date = 2016-11-16 | archive-date = 2016-11-17 | archive-url = https://web.archive.org/web/20161117001823/https://einsteinathome.org/account/141782 | url-status = live }}</ref> Fekete improved the official S4 application and introduced [[Streaming SIMD Extensions|SSE]], [[3DNow!]] and [[SSE3]] optimizations into the code improving performance by up to 800%.<ref name="akosf optimization">{{cite web |url=https://einsteinathome.org/content/new-optimised-executables-links-read-only-thread#28668 |title=New Optimised Executables Links |access-date=2016-11-16 |archive-date=2016-11-17 |archive-url=https://web.archive.org/web/20161117001724/https://einsteinathome.org/content/new-optimised-executables-links-read-only-thread#28668 |url-status=live }}</ref> Fekete was recognized for his efforts and was afterward officially involved with the Einstein@Home team in the development of the new S5 application.<ref name="NewScientist">{{cite web | url = https://www.newscientist.com/article/dn9180-programmer-speeds-search-for-gravitational-waves.html | title = Programmer speeds search for gravitational waves | publisher = [[New Scientist]] | access-date = 2009-07-01 | date = 2006-05-17 | archive-date = 2015-05-11 | archive-url = https://web.archive.org/web/20150511211322/http://www.newscientist.com/article/dn9180-programmer-speeds-search-for-gravitational-waves.html | url-status = live }}</ref> As of late July 2006, this new official application had become widely distributed among Einstein@Home users. The app created a large surge in the project's total performance and productivity, as measured by floating point speed (or [[FLOPS]]), which over time has increased by approximately 50% compared to non-optimized S4 applications.<ref name="Graphical display of progress on S5">{{cite web | url = http://homepage.hispeed.ch/einstein | title = Einstein@home Server Status | access-date = 2006-08-22 | url-status = dead | archive-url = https://web.archive.org/web/20060820122101/http://homepage.hispeed.ch/einstein/ | archive-date = 2006-08-20}}</ref>

The first Einstein@Home analysis of the early LIGO S5 data set, where the instruments initially reached their design sensitivity, began on 15 June 2006. This search used 22 segments of 30 hours each from the LIGO Hanford 4-km detector and six segments of 30 hours from the LIGO Livingston 4-km detector. This analysis run (code name "S5R1"), employing the search methodology as Einstein@Home, was very similar to the previous S4 analysis. However, the search results were more sensitive due to the use of more data of better quality compared to S4. Over large parts of the search parameter space, these results, which also appeared in [[Physical Review|Physical Review D]], are the most exhaustive published to date.<ref name="EaHS5R1">{{cite journal | journal = [[Physical Review D]] | volume = 80 | issue = 4 | page = 042003 |doi=10.1103/PhysRevD.80.042003 | title = Einstein@Home search for periodic gravitational waves in early S5 LIGO data|bibcode = 2009PhRvD..80d2003A |arxiv = 0905.1705 | year = 2009 | last1 = Abbott | first1 = B. P. | s2cid = 13364107 | display-authors = etal}}</ref>

The second Einstein@Home search of LIGO S5 data (code name "S5R3") constituted a further major improvement regarding search sensitivity.<ref>{{cite web | author=Reinhard Prix | url=https://einsteinathome.org/content/s5r3-search-strategy#75618 | title=S5R3 search strategy | access-date=2016-11-16 | archive-date=2016-11-17 | archive-url=https://web.archive.org/web/20161117064506/https://einsteinathome.org/content/s5r3-search-strategy#75618 | url-status=live }}</ref> As opposed to previous searches, the ensuing results were already combined ''on the volunteers' computers'' via a [[Hough transform]] technique. This method matched-filtered results from 84 data segments of 25 hours each, parameters from which came from both 4-km LIGO Hanford and Livingston instruments.

On 7 May 2010, a new Einstein@Home search (code name "S5GC1"), which uses a significantly improved search method, launched. This program analyzed 205 data segments of 25 hours each, using data from both 4-km LIGO Hanford and Livingston instruments. It employed a technique which exploited global parameter-space correlations to efficiently combine the matched-filtering results from the different segments.<ref name="CWsearch" /><ref name="GCT">{{cite journal | journal = [[Physical Review Letters]] |volume = 103 |issue = 18 |page=181102 |doi=10.1103/PhysRevLett.103.181102 |title = Exploiting Large-Scale Correlations to Detect Continuous Gravitational Waves |author=Holger J. Pletsch |author2=Bruce Allen |bibcode= 2009PhRvL.103r1102P |arxiv = 0906.0023 |pmid=19905796 |year = 2009|s2cid = 40560957 }}</ref>

Results from an Einstein@Home all-sky search for continuous gravitational waves in LIGO S5 data were published on 13 February 2013.<ref>{{Cite journal|last1=The LIGO Scientific Collaboration and the Virgo Collaboration|last2=Aasi|first2=J.|last3=Abadie|first3=J.|last4=Abbott|first4=B. P.|last5=Abbott|first5=R.|last6=Abbott|first6=T. D.|last7=Abernathy|first7=M.|last8=Accadia|first8=T.|last9=Acernese|first9=F.|last10=Adams|first10=C.|last11=Adams|first11=T.|date=2013-02-13|title=Einstein@Home all-sky search for periodic gravitational waves in LIGO S5 data|url=https://link.aps.org/doi/10.1103/PhysRevD.87.042001|journal=Physical Review D|volume=87|issue=4|pages=042001|doi=10.1103/PhysRevD.87.042001|arxiv=1207.7176|bibcode=2013PhRvD..87d2001A|s2cid=119095704|access-date=2021-06-22|archive-date=2022-09-05|archive-url=https://web.archive.org/web/20220905052056/https://journals.aps.org/prd/abstract/10.1103/PhysRevD.87.042001|url-status=live}}</ref> In the most sensitive frequency band of the search (a half-Hertz band at 152.5 Hertz), the presence of periodic gravitational waves with strain amplitude larger than 7.6×10<sup>−25</sup> could be excluded at 90% [[Confidence interval|confidence]]. Overall, the search was 3 times as sensitive as previous Einstein@Home searches in LIGO S5 data. Details of the two-stage follow-up procedure for signal candidates used in this study were published on 25 June 2014.<ref>{{Cite journal|last1=Shaltev|first1=M.|last2=Leaci|first2=P.|last3=Papa|first3=M. A.|author3-link=M. Alessandra Papa|last4=Prix|first4=R.|date=2014-06-25|title=Fully coherent follow-up of continuous gravitational-wave candidates: An application to Einstein@Home results|url=https://link.aps.org/doi/10.1103/PhysRevD.89.124030|journal=Physical Review D|volume=89|issue=12|pages=124030|doi=10.1103/PhysRevD.89.124030|arxiv=1405.1922|bibcode=2014PhRvD..89l4030S|s2cid=119204543}}</ref>

A search for high-frequency (1249 Hertz to 1499 Hertz) continuous gravitational waves in LIGO S5 data by Einstein@Home, published on 26 September 2016, was the only such search in LIGO data. No signal candidates were identified. The search excluded neutron stars with spin frequencies between 625 Hertz and 770 Hertz and with ellipticities greater than 2.8×10<sup>−7</sup> closer than 100 parsec to Earth.

Data from LIGO 6th science run (S6) were analyzed by Einstein@Home and the results were published on 18 November 2016.<ref>{{Cite journal|last1=LIGO Scientific Collaboration and Virgo Collaboration|last2=Abbott|first2=B. P.|last3=Abbott|first3=R.|last4=Abbott|first4=T. D.|last5=Abernathy|first5=M. R.|last6=Acernese|first6=F.|last7=Ackley|first7=K.|last8=Adams|first8=C.|last9=Adams|first9=T.|last10=Addesso|first10=P.|last11=Adhikari|first11=R. X.|date=2016-11-18|title=Results of the deepest all-sky survey for continuous gravitational waves on LIGO S6 data running on the Einstein@Home volunteer distributed computing project|url=https://link.aps.org/doi/10.1103/PhysRevD.94.102002|journal=Physical Review D|volume=94|issue=10|pages=102002|doi=10.1103/PhysRevD.94.102002|arxiv=1606.09619|bibcode=2016PhRvD..94j2002A|hdl=1721.1/106227|s2cid=118385297|hdl-access=free|access-date=2021-06-22|archive-date=2022-09-05|archive-url=https://web.archive.org/web/20220905052056/https://journals.aps.org/prd/abstract/10.1103/PhysRevD.94.102002|url-status=live}}</ref> No signal was found and the search set the most stringent upper limits for an all-sky search for continuous gravitational waves at the time of publication. In the most sensitive frequency band between 170.5 Hertz and 171 Hertz there were (with 90% confidence) no continuous gravitational waves with a strain amplitude of more than 5.5×10<sup>−25</sup> detected. At frequencies of 230 Hertz, the search results exclude neutron stars with ellipticities greater than 10<sup>−6</sup> within 100 parsecs of Earth.

Einstein@Home conducted a directed search for continuous gravitational waves from the central object in the supernova remnant [[Cassiopeia A]].<ref>{{Cite journal|last1=Zhu|first1=Sylvia J.|last2=Papa|first2=Maria Alessandra|author2-link=M. Alessandra Papa|last3=Eggenstein|first3=Heinz-Bernd|last4=Prix|first4=Reinhard|last5=Wette|first5=Karl|last6=Allen|first6=Bruce|last7=Bock|first7=Oliver|last8=Keitel|first8=David|last9=Krishnan|first9=Badri|last10=Machenschalk|first10=Bernd|last11=Shaltev|first11=Miroslav|date=2016-10-28|title=Einstein@Home search for continuous gravitational waves from Cassiopeia A|url=https://link.aps.org/doi/10.1103/PhysRevD.94.082008|journal=Physical Review D|volume=94|issue=8|pages=082008|doi=10.1103/PhysRevD.94.082008|arxiv=1608.07589|bibcode=2016PhRvD..94h2008Z|s2cid=118479596|access-date=2021-06-22|archive-date=2022-09-05|archive-url=https://web.archive.org/web/20220905052054/https://journals.aps.org/prd/abstract/10.1103/PhysRevD.94.082008|url-status=live}}</ref> It used data from the LIGO S6 run and searched over a range of frequencies from 50 Hertz to 1000 Hertz, because the spin frequency of the central object is unknown. No signal was found. The upper limits on gravitational-wave emission from Cassiopeia A were the most stringent at the time of publication, about a factor two lower than previous upper limits.

On 28 December 2016 results from a follow-up of the all-sky search for continuous gravitational waves in LIGO S6 data were published.<ref>{{Cite journal|last1=Papa|first1=Maria Alessandra|author1-link=M. Alessandra Papa|last2=Eggenstein|first2=Heinz-Bernd|last3=Walsh|first3=Sinéad|last4=Di Palma|first4=Irene|last5=Allen|first5=Bruce|last6=Astone|first6=Pia|last7=Bock|first7=Oliver|last8=Creighton|first8=Teviet D.|last9=Keitel|first9=David|last10=Machenschalk|first10=Bernd|last11=Prix|first11=Reinhard|date=2016-12-28|title=Hierarchical follow-up of subthreshold candidates of an all-sky Einstein@Home search for continuous gravitational waves on LIGO sixth science run data|url=https://link.aps.org/doi/10.1103/PhysRevD.94.122006|journal=Physical Review D|volume=94|issue=12|pages=122006|doi=10.1103/PhysRevD.94.122006|arxiv=1608.08928|bibcode=2016PhRvD..94l2006P|s2cid=4595158|access-date=2021-06-22|archive-date=2022-09-05|archive-url=https://web.archive.org/web/20220905052056/https://journals.aps.org/prd/abstract/10.1103/PhysRevD.94.122006|url-status=live}}</ref> Out of a total of 3.8 × 10<sup>10</sup> signal candidates from the earlier search, the 16 million most promising were analyzed using a four-stage hierarchical process. No candidate was found to be consistent with an astrophysical source of continuous gravitational waves. In the frequency band between 170.5 Hertz and 171 Hertz the upper limit (90% confidence) on the strain amplitude was 4.3×10<sup>−25</sup>, a factor 1.3 lower than in the previous search.

Searches for continuous gravitational waves are limited by the available computing power. Within the project, research on improving the sensitivity of the searches with new methods is conducted. In late 2017 two publications were published, describing improved methods of candidate clustering in the hierarchical searches and new "veto" methods that distinguish between astrophysical continuous gravitational waves and detector artifacts mimicking them.<ref>{{Cite journal|last1=Zhu|first1=Sylvia J.|last2=Papa|first2=Maria Alessandra|author2-link=M. Alessandra Papa|last3=Walsh|first3=Sinéad|date=2017-12-08|title=New veto for continuous gravitational wave searches|url=https://link.aps.org/doi/10.1103/PhysRevD.96.124007|journal=Physical Review D|volume=96|issue=12|pages=124007|doi=10.1103/PhysRevD.96.124007|arxiv=1707.05268|bibcode=2017PhRvD..96l4007Z|s2cid=118918979|access-date=2021-06-22|archive-date=2022-09-05|archive-url=https://web.archive.org/web/20220905052055/https://journals.aps.org/prd/abstract/10.1103/PhysRevD.96.124007|url-status=live}}</ref><ref>{{Cite journal|last1=Singh|first1=Avneet|last2=Papa|first2=Maria Alessandra|author2-link=M. Alessandra Papa|last3=Eggenstein|first3=Heinz-Bernd|last4=Walsh|first4=Sinéad|date=2017-10-16|title=Adaptive clustering procedure for continuous gravitational wave searches|url=https://link.aps.org/doi/10.1103/PhysRevD.96.082003|journal=Physical Review D|volume=96|issue=8|pages=082003|doi=10.1103/PhysRevD.96.082003|arxiv=1707.02676|bibcode=2017PhRvD..96h2003S|s2cid=119694728|access-date=2021-06-22|archive-date=2022-09-05|archive-url=https://web.archive.org/web/20220905052055/https://journals.aps.org/prd/abstract/10.1103/PhysRevD.96.082003|url-status=live}}</ref>

Both these new methods were employed in the first Einstein@Home all-sky search for continuous gravitational waves in Advanced LIGO data from the first observing run (O1), the results of which were published on 8 December 2017.<ref>{{Cite journal|last1=LIGO Scientific Collaboration and Virgo Collaboration|last2=Abbott|first2=B. P.|last3=Abbott|first3=R.|last4=Abbott|first4=T. D.|last5=Acernese|first5=F.|last6=Ackley|first6=K.|last7=Adams|first7=C.|last8=Adams|first8=T.|last9=Addesso|first9=P.|last10=Adhikari|first10=R. X.|last11=Adya|first11=V. B.|date=2017-12-08|title=First low-frequency Einstein@Home all-sky search for continuous gravitational waves in Advanced LIGO data|url=https://link.aps.org/doi/10.1103/PhysRevD.96.122004|journal=Physical Review D|volume=96|issue=12|pages=122004|doi=10.1103/PhysRevD.96.122004|arxiv=1707.02669|bibcode=2017PhRvD..96l2004A|hdl=1721.1/112761|s2cid=3217050|hdl-access=free|access-date=2021-06-22|archive-date=2022-09-05|archive-url=https://web.archive.org/web/20220905052056/https://journals.aps.org/prd/abstract/10.1103/PhysRevD.96.122004|url-status=live}}</ref> The first part of the search investigated the lower end of the LIGO frequency band between 20 Hertz and 100 Hertz. No signals were found. The most stringent upper limit (90% confidence) on the gravitational-wave strain amplitude set by the search was 1.8×10<sup>−25</sup> at a frequency of 100 Hertz.

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.<ref>{{Cite journal|last1=Ming|first1=Jing|last2=Papa|first2=Maria Alessandra|author2-link=M. Alessandra Papa|last3=Krishnan|first3=Badri|last4=Prix|first4=Reinhard|last5=Beer|first5=Christian|last6=Zhu|first6=Sylvia J.|last7=Eggenstein|first7=Heinz-Bernd|last8=Bock|first8=Oliver|last9=Machenschalk|first9=Bernd|date=2018-01-31|title=Optimally setting up directed searches for continuous gravitational waves in Advanced LIGO O1 data|url=https://link.aps.org/doi/10.1103/PhysRevD.97.024051|journal=Physical Review D|volume=97|issue=2|pages=024051|doi=10.1103/PhysRevD.97.024051|arxiv=1708.02173|bibcode=2018PhRvD..97b4051M|s2cid=119223919|access-date=2021-06-22|archive-date=2022-09-05|archive-url=https://web.archive.org/web/20220905052056/https://journals.aps.org/prd/abstract/10.1103/PhysRevD.97.024051|url-status=live}}</ref> It describes the design of searches for continuous gravitational waves over a wide frequency range from three supernova remnants ([[RX J0852.0−4622|Vela Jr]], [[Cassiopeia A]], and [[SN 393|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.<ref>{{Cite journal|last1=Ming|first1=J.|last2=Papa|first2=M. A.|author2-link=M. Alessandra Papa|last3=Singh|first3=A.|last4=Eggenstein|first4=H.-B.|last5=Zhu|first5=S. J.|last6=Dergachev|first6=V.|last7=Hu|first7=Y.|last8=Prix|first8=R.|last9=Machenschalk|first9=B.|last10=Beer|first10=C.|last11=Behnke|first11=O.|date=2019-07-29|title=Results from an Einstein@Home search for continuous gravitational waves from Cassiopeia A, Vela Jr., and G347.3|url=https://link.aps.org/doi/10.1103/PhysRevD.100.024063|journal=Physical Review D|volume=100|issue=2|pages=024063|doi=10.1103/PhysRevD.100.024063|arxiv=1903.09119|bibcode=2019PhRvD.100b4063M|s2cid=84842778|access-date=2021-06-22|archive-date=2022-09-05|archive-url=https://web.archive.org/web/20220905052056/https://journals.aps.org/prd/abstract/10.1103/PhysRevD.100.024063|url-status=live}}</ref> 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.<ref>{{Cite journal|last1=Papa|first1=M. A.|author1-link=M. Alessandra Papa|last2=Ming|first2=J.|last3=Gotthelf|first3=E. V.|last4=Allen|first4=B.|last5=Prix|first5=R.|last6=Dergachev|first6=V.|last7=Eggenstein|first7=H.-B.|last8=Singh|first8=A.|last9=Zhu|first9=S. J.|date=2020-06-29|title=Search for Continuous Gravitational Waves from the Central Compact Objects in Supernova Remnants Cassiopeia A, Vela Jr., and G347.3–0.5|journal=The Astrophysical Journal|language=en|volume=897|issue=1|pages=22|doi=10.3847/1538-4357/ab92a6|issn=1538-4357|arxiv=2005.06544|bibcode=2020ApJ...897...22P|s2cid=218630012|doi-access=free }}</ref> 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.<ref>{{Cite journal|last1=Steltner|first1=B.|last2=Papa|first2=M. A.|author2-link=M. Alessandra Papa|last3=Eggenstein|first3=H.-B.|last4=Allen|first4=B.|last5=Dergachev|first5=V.|last6=Prix|first6=R.|last7=Machenschalk|first7=B.|last8=Walsh|first8=S.|last9=Zhu|first9=S. J.|last10=Behnke|first10=O.|last11=Kwang|first11=S.|date=2021-03-01|title=Einstein@Home All-sky Search for Continuous Gravitational Waves in LIGO O2 Public Data|journal=The Astrophysical Journal|language=en|volume=909|issue=1|pages=79|doi=10.3847/1538-4357/abc7c9|issn=0004-637X|arxiv=2009.12260|bibcode=2021ApJ...909...79S|s2cid=221949218|doi-access=free }}</ref> 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<sup>−25</sup>. 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<sup>−7</sup> (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.<ref>{{cite journal|last1=Ming|first1=Jing|last2=Papa|first2=Maria Alessandra|author2-link=M. Alessandra Papa|last3=Eggenstein|first3=Heinz-Bernd|last4=Machenschalk|first4=Bernd|last5=Steltner|first5=Benjamin|last6=Prix|first6=Reinhard|last7=Allen|first7=Bruce|last8=Behnke|first8=Oliver|title=Results from an Einstein@Home Search for Continuous Gravitational Waves from G347.3 at Low Frequencies in LIGO O2 Data|journal=The Astrophysical Journal |year=2022 |volume=925 |issue=1 |page=8 |doi=10.3847/1538-4357/ac35cb |arxiv=2108.02808|bibcode=2022ApJ...925....8M |s2cid=236950673 |doi-access=free }}</ref> 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<sup>−6</sup> 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<sup>−26</sup>.

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&nbsp;Hertz and 800&nbsp;Hertz and with spin-downs of up to −2.6×10<sup>−9</sup>&nbsp;Hz&nbsp;s<sup>−1</sup>.<ref>{{Cite journal |last1=Steltner |first1=B. |last2=Papa |first2=M. A. |last3=Eggenstein |first3=H.-B. |last4=Prix |first4=R. |last5=Bensch |first5=M. |last6=Allen |first6=B. |last7=Machenschalk |first7=B. |date=2023-07-01 |title=Deep Einstein@Home All-sky Search for Continuous Gravitational Waves in LIGO O3 Public Data |journal=The Astrophysical Journal |volume=952 |issue=1 |pages=55 |doi=10.3847/1538-4357/acdad4 |arxiv=2303.04109 |bibcode=2023ApJ...952...55S |issn=0004-637X |doi-access=free }}</ref> 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&nbsp;Hertz with ellipticities larger than 5×10<sup>−8</sup> closer than 100&nbsp;parsec.