TY - JOUR

T1 - Measuring the eccentricity of GW170817 and GW190425

AU - Lenon, Amber K.

AU - Nitz, Alexander H.

AU - Brown, D. A.

N1 - Funding Information: We acknowledge the Max Planck Gesellschaft for support and the Atlas cluster computing team at the Albert-Einstein-Institut in Hannover. This research was supported in part by the National Science Foundation under grant no. PHY-1748958. Duncan Brown thanks National Science Foundation grant no. PHY-1707954 for support. Amber Lenon thanks National Science Foundation grant no. AST-1559694 for support. This research has made use of data, software, and/or web tools obtained from the Gravitational Wave Open Science Center (https://www.gw-openscience.org), a service of LIGO Laboratory, the LIGO Scientific Collaboration, and the Virgo Collaboration. LIGO is funded by the U.S. National Science Foundation. Virgo is funded by the French Centre National de Recherche Scientifique (CNRS), the Italian Istituto Nazionale della Fisica Nucleare (INFN), and the Dutch Nikhef, with contributions by Polish and Hungarian institutes.

PY - 2020/7/20

Y1 - 2020/7/20

N2 - Two binary neutron star mergers, GW170817 and GW190425, have been detected by Advanced LIGO and Virgo. These signals were detected by matched-filter searches that assume that the star's orbit has circularized by the time their gravitational-wave emission is observable. This suggests that their eccentricity is low, but full parameter estimation of their eccentricity has not yet been performed. We use gravitational-wave observations to measure the eccentricity of GW170817 and GW190425. We find that the eccentricity at a gravitational-wave frequency of 10 Hz is e = 0.024 and e = 0.048 for GW170817 and GW190425, respectively (90 per cent confidence). This is consistent with the binaries being formed in the field, as such systems are expected to have circularized to e = 10-4 by the time they reach the LIGO-Virgo band. Our constraint is a factor of 2 smaller that an estimate based on GW170817 being detected by searches that neglect eccentricity. However, we caution that we find significant prior dependence in our limits, suggesting that there is limited information in the signals. We note that other techniques used to constrain binary neutron star eccentricity without full parameter estimation may miss degeneracies in the waveform, and that for future signals, it will be important to perform full parameter estimation with accurate waveform templates.

AB - Two binary neutron star mergers, GW170817 and GW190425, have been detected by Advanced LIGO and Virgo. These signals were detected by matched-filter searches that assume that the star's orbit has circularized by the time their gravitational-wave emission is observable. This suggests that their eccentricity is low, but full parameter estimation of their eccentricity has not yet been performed. We use gravitational-wave observations to measure the eccentricity of GW170817 and GW190425. We find that the eccentricity at a gravitational-wave frequency of 10 Hz is e = 0.024 and e = 0.048 for GW170817 and GW190425, respectively (90 per cent confidence). This is consistent with the binaries being formed in the field, as such systems are expected to have circularized to e = 10-4 by the time they reach the LIGO-Virgo band. Our constraint is a factor of 2 smaller that an estimate based on GW170817 being detected by searches that neglect eccentricity. However, we caution that we find significant prior dependence in our limits, suggesting that there is limited information in the signals. We note that other techniques used to constrain binary neutron star eccentricity without full parameter estimation may miss degeneracies in the waveform, and that for future signals, it will be important to perform full parameter estimation with accurate waveform templates.

KW - Binaries: general

KW - Gravitational waves

KW - Stars: neutron

UR - http://www.scopus.com/inward/record.url?scp=85093535495&partnerID=8YFLogxK

U2 - 10.48550/arXiv.2005.14146

DO - 10.48550/arXiv.2005.14146

M3 - Article

AN - SCOPUS:85093535495

VL - 497

SP - 1966

EP - 1971

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 2

ER -