The Nanograv Nine-Year Data Set: Mass and Geometric Measurements of Binary Millisecond Pulsars

Abstract

We analyze 24 binary radio pulsars in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) nine-year data set. We make fourteen significant measurements of Shapiro delay, including new detections in four pulsar-binary systems (PSRs J0613−0200, J2017+0603, J2302+4442, and J2317+1439), and derive estimates of the binary-component masses and orbital inclination for these MSP-binary systems. We find a wide range of binary pulsar masses, with values as low as m p = 1.18 +0.10 −0.09 M for PSR J1918−0642 and as high as m p = 1.928 +0.017 −0.017 M for PSR J1614−2230 (both 68.3% credibility). We make an improved measurement of the Shapiro timing delay in the PSR J1918−0642 and J2043+1711 systems, measuring the pulsar mass in the latter system to be m p = 1.41 +0.21 −0.18 M (68.3% credibility) for the first time. We measure secular variations of one or more orbital elements in many systems, and use these measurements to further constrain our estimates of the pulsar and companion masses whenever possible. In particular, we used the observed Shapiro delay and periastron advance due to relativistic gravity in the PSR J1903+0327 system to derive a pulsar mass of m p = 1.65 +0.02 −0.02 M (68.3% credibility). We discuss the implications that our mass measurements have on the overall neutron-star mass distribution, and on the "mass/orbital-period" correlation due to extended mass transfer.

Simultaneous Chiral Symmetry Restoration and Deconfinement Consequences for the QCD Phase Diagram

“…In such a case, they represent a uniform background, which does not influence the phase transition. As pointed out in Klähn & Fischer (2015), this requires repulsive vector interactions as provided by vBag in order to describe a maximum neutron star mass of about 2M e , which is in agreement with the results of Antoniadis et al (2013) and Fonseca et al (2016). The inset of Figure 7 shows that vBag provides such massive neutron stars for a vector coupling constant of >´-K 2 10 v 6 MeV −2 .…”

“…Although vBag is initially motivated as a simplification of an NJL model with scalar and iso-vector condensates, it is essentially an extended bag model that explicitly accounts for the repulsive vector interaction. This property is essential for a stiffening of the EoS toward high densities and results in maximum neutron star masses in agreement with the current constraint of about 2M e from the observations of Antoniadis et al (2013) and Demorest et al (2010), the latter recently revised to 1.928±0.017M e by Fonseca et al (2016). Moreover, vBag mimics (de)confinement via a phenomenological pressure correction to the EoS in the form of a deconfinement bag constant B dc .…”

The Identification of the White Dwarf Companion to the Millisecond Pulsar J2317+1439

“…Table 1 Parameters of PSR J2317+1439 and photometric results of the companion. The timing, astrometric and orbital parameters are from Desvignes et al (2016), Matthews et al (2016) and Fonseca et al (2016). The extinction (A λ ) is estimated using models by Green et al (2015) and coefficients from Schlafly & Finkbeiner (2011).…”

Strange matter prospects within the string-flip model

“…In particular, the appearance of additional particle degrees of freedom, such as hyperons or the transition to the quark-gluon plasma, are challenged by the observations of pulsars with masses on the order of 2 M [1][2][3], as they tend to generally soften the equation of state (EOS). Despite the yet unresolved hyperon problem, it has been demonstrated recently that vector repulsion between quarks in the deconfined phase provides the necessary stiffness to yield massive neutron stars of 2 M or more [4][5][6].…”