Abbott, B. P.Davies, G. S.LIGO Scientific Collaboration and Virgo Collaboration2017-04-052017-04-052016-06Abbott BP, et al., (LIGO Scientific Collaboration and Virgo Collaboration). (2016) Improved analysis of GW150914 using a fully spin-precessing waveform model. Physical Reviews X, Volume 6, Issue 4, October - December 2016, Article number 041014http://dspace.lib.cranfield.ac.uk/handle/1826/11724https://doi.org/10.1103/PhysRevX.6.041014This paper presents updated estimates of source parameters for GW150914, a binary black-hole coalescence event detected by the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015 [Abbott et al. Phys. Rev. Lett. 116, 061102 (2016).]. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] presented parameter estimation of the source using a 13-dimensional, phenomenological precessing-spin model (precessing IMRPhenom) and an 11-dimensional nonprecessing effective-one-body (EOB) model calibrated to numerical-relativity simulations, which forces spin alignment (nonprecessing EOBNR). Here, we present new results that include a 15-dimensional precessing-spin waveform model (precessing EOBNR) developed within the EOB formalism. We find good agreement with the parameters estimated previously [Abbott et al. Phys. Rev. Lett. 116, 241102 (2016).], and we quote updated component masses of 35 + 5 − 3 M ⊙ and 3 0 + 3 − 4 M ⊙ (where errors correspond to 90% symmetric credible intervals). We also present slightly tighter constraints on the dimensionless spin magnitudes of the two black holes, with a primary spin estimate < 0.65 and a secondary spin estimate < 0.75 at 90% probability. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] estimated the systematic parameter-extraction errors due to waveform-model uncertainty by combining the posterior probability densities of precessing IMRPhenom and nonprecessing EOBNR. Here, we find that the two precessing-spin models are in closer agreement, suggesting that these systematic errors are smaller than previously quoted.Attribution 3.0 Internationalhttp://creativecommons.org/licenses/by/3.0/Article