Maximum mass and universal relations of rotating relativistic hybrid hadron-quark stars

Abstract

We construct equilibrium models of uniformly and differentially rotating hybrid hadron-quark stars using equations of state (EOSs) with a first-order phase transition that gives rise to a third family of compact objects. We find that the ratio of the maximum possible mass of uniformly rotating configurationsthe supramassive limit -to the Tolman-Oppenheimer-Volkoff (TOV) limit mass is not EOS-independent, and is between 1.15 and 1.31, in contrast with the value of 1.20 previously found for hadronic EOSs. Therefore, some of the constraints placed on the EOS from the observation of the gravitational wave event GW170817 do not apply to hadron-quark EOSs. However, the supramassive limit mass for the family of EOSs we treat is consistent with limits set by GW170817, strengthening the possibility of interpreting GW170817 with a hybrid hadron-quark EOSs. We also find that along constant angular momentum sequences of uniformly rotating stars, the third family maximum and minimum mass models satisfy approximate EOS-independent relations, and the supramassive limit of the third family is approximately 16.5 % larger than the third family TOV limit. For differentially rotating spheroidal stars, we find that a lower-limit on the maximum supportable rest mass is 123 % more than the TOV limit rest mass. Finally, we verify that the recently discovered universal relations relating angular momentum, rest mass and gravitational mass for turning-point models hold for hybrid hadron-quark EOSs when uniform rotation is considered, but have a clear dependence on the degree of differential rotation. PACS. 04.40.Dg Relativistic stars: structure, and stability arXiv:1905.00028v1 [astro-ph.HE] 30 Apr 2019 4 Note that this result is in tension with what was found in [85] where different equations of state were adopted. M ↓ M TOV ↓ = 1 + 0.33 J J ↓,Kep 2 − 0.10 J J ↓,Kep 4 . (19)The spread in this equation is at most 2 %. 10 Moreover, we find that the bottom turning points can be described with the same Equations (18), but with a spread of 3 %. The universality becomes tighter if we consider top and bottom turning points separately. For the bottom turning points, the best-fitting functions are M ↓ M TOV ↓ = 1 + 0.35 J M TOV ↓ 2 2 − 0.12 J M TOV ↓ 2 4 , (20a) M 0,↓ M TOV 0,↓ = 1 + 0.58 J M TOV 0,↓ 2 2 − 0.35 J M TOV 0,↓ 2 4

Astrophysical Aspects of General Relativistic Mass Twin Stars

“…]. We confirm the finding of [Bozzola et al (2019)] that the coefficient spans a range of values for which we find 1.16 < α < 1.33, see the table 1.8. The lower limit in (1.72) comes from the new high-mass pulsar PSR J0740+6620 for which a mass 2.17 +0.11 −0.10 M has been determined by Cromartie et al (2019) by measuring the Shapiro delay, and the upper limit in our case is 2.23 M for the lowest value of α = 1.16.…”

“…The scenario of a delayed collapse to a black hole is of special importance for interpreting GW170817 and will therefore be discussed below in further detail. In this context appears the question whether between the above-introduced characteristic masses at maximal and at zero rotation frequency hold EoS-independent, so-called universal relations that have been investigated for the maximum mass of hadronic EoS [Bozzola et al (2018); Rezzolla et al (2018)] and recently also for hybrid EoS including the Maxwell construction cases of ACB4 and ACB5 [Bozzola et al (2019)]. We shall come back to this issue below.…”

“…The hypothesis that the relation (1.71) can be extended to include hybrid stars with a strong phase transition and even with third family sequences has recently been investigated in Ref. [Bozzola et al (2019) (1.72)…”

Neutron-star tidal deformability and equation-of-state constraints

“…Using a similar interpretation, a relation between the radius, the maximum neutron star mass, and the threshold mass for prompt collapse of the merger remnant [293] suggests R 1.6 10.6km [220]. The arguments leading to the above constraints rely on equations of state without strong phase transitions and the possibility of hybrid quark-hadron stars [294][295][296], however, detection of further systems can provide stronger constraints or put the above expectations to the test [297].…”

Accretion‐induced collapse to third family compact stars as trigger for eccentric orbits of millisecond pulsars in binaries

“…The four‐polytrope model which was introduced in Paschalidis et al () and denoted there as “ACB5” fulfills the present constraints from multimessenger astronomy on maximum mass and compactness of compact stars (given at the end of the Introduction) and has also been recently studied concerning its behavior under fast rotation (Blaschke et al ; Bozzola et al ). In Table , we provide the parameters of this EoS.…”