Constraining the Dense Matter Equation of State with Joint Analysis of NICER and LIGO/Virgo Measurements

Creators: Raaijmakers, G.; Greif, S. K.; Riley, T. E.; Hinderer, T.; Hebeler, K.; Schwenk, A.; Watts, A. L.; Nissanke, S.; Guillot, S.; Lattimer, J. M.; Ludlam, R. M.

Abstract

The Neutron Star Interior Composition Explorer collaboration recently published a joint estimate of the mass and the radius of PSR J0030+0451, derived via X-ray pulse-profile modeling. Raaijmakers et al. explored the implications of this measurement for the dense matter equation of state (EOS) using two parameterizations of the high-density EOS: a piecewise-polytropic model, and a model based on the speed of sound in neutron stars (NSs). In this work we obtain further constraints on the EOS following this approach, but we also include information about the tidal deformability of NSs from the gravitational wave signal of the compact binary merger GW170817. We compare the constraints on the EOS to those set by the recent measurement of a 2.14 M⊙ pulsar, included as a likelihood function approximated by a Gaussian, and find a small increase in information gain. To show the flexibility of our method, we also explore the possibility that GW170817 was a NS–black hole merger, which yields weaker constraints on the EOS.

Additional Information

© 2020 The American Astronomical Society. Received 2019 December 24; revised 2020 March 17; accepted 2020 March 23; published 2020 April 13. We thank the anonymous referee for comments that helped to improve this work. This work was supported in part by NASA through the NICER mission and the Astrophysics Explorers Program. G.R., T.H., and S.N. are grateful for support from the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) through the VIDI and Projectruimte grants (PI Nissanke). T.E.R. and A.L.W. acknowledge support from ERC Starting grant No. 639217 CSINEUTRONSTAR (PI Watts). This work was sponsored by NWO Exact and Natural Sciences for the use of supercomputer facilities, and was carried out on the Dutch national e-infrastructure with the support of SURF Cooperative. S.K.G., K.H., and A.S. acknowledge support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 279384907—SFB 1245. S.G. acknowledges the support of the CNES. R.M.L. acknowledges the support of NASA through Hubble Fellowship Program grant HST-HF2-51440.001. J.M.L. acknowledges support by NASA through the NICER mission with Grant 80NSSC17K0554 and by the U.S. DOE through Grant DE-FG02-87ER40317. This research has made extensive use of NASA's Astrophysics Data System Bibliographic Services (ADS) and the arXiv. We thank Jocelyn Read, Wynn Ho, and Cole Miller for comments on a draft manuscript. Software: Python/C language (Oliphant 2007), GNU Scientific Library (GSL; Gough 2009), NumPy (van der Walt et al. 2011), Cython (Behnel et al. 2011), SciPy (Jones et al. 2001), MPI (Forum 1994), MPI for Python (Dalcín et al. 2008), Matplotlib (Hunter 2007; Droettboom et al. 2018), IPython (Perez & Granger 2007), Jupyter (Kluyver et al. 2016), MultiNest (Feroz et al. 2009), PyMultiNest (Buchner et al. 2014).

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