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Register a new userThe missing compact star of SN1987A: a solid quark star?
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To investigate the missing compact star of Supernova 1987A, we analyzed both the cooling and the heating processes of a possible compact star based on the upper limit of observational X-ray luminosity. From the cooling process we found that a solid quark-cluster star, which has a stiffer equation of state than that of conventional liquid quark star, has a heat capacity much smaller than a neutron star. It can cool down quickly, which can naturally explain the non-detection of a point source (neutron star or quark star) in X-ray band. On the other hand, we consider the heating process from magnetospheric activity and possible accretion, and obtain some constraints to the parameters of a possible pulsar. We conclude that a solid quark-cluster star can be fine with the observational limit in a large and acceptable parameter space. A pulsar with a short period and a strong magnetic field (or with a long period and a weak field) would has luminosity higher than the luminosity limit if the optical depth is not large enough to hide the compact star. The constraints of the pulsar parameters can be tested if the central compact object in 1987A is discovered by advanced facilities in the future.
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The detection of an unexpected $sim 2.5 M_{odot}$ component in the gravitational wave event GW190814 has puzzled the community of High-Energy astrophysicists, since in the absence of further information it is not clear whether this is the heaviest neutron star ever detected or either the lightest black hole known, of a kind absent in the local neighbourhood. We show in this work a few possibilities for a model of the former, in the framework of three different quark matter models with and without anisotropy in the interior pressure. As representatives of classes of exotic solutions, we show that even though the stellar sequences may reach this ballpark, it is difficult to fulfill simultaneously the constraint of the radius as measured by the NICER team for the pulsar PSR J0030+0451. Thus, and assuming both measurements stand, compact neutron stars can not be all made of self-bound quark matter, even within anisotropic solutions which boost the maximum mass well above the $sim 2.5 M_{odot}$ figure. We also point out that a very massive compact star will limit the absolute maximum matter density in the present Universe to be less than 6 times the nuclear saturation value.
There are strong indications that the process of conversion of a neutron star into a strange quark star proceeds as a strong deflagration implying that in a few milliseconds almost the whole star is converted. Starting from the three-dimensional hydrodynamic simulations of the combustion process which provide the temperature profiles inside the newly born strange star, we calculate for the first time the neutrino signal that is to be expected if such a conversion process takes place. The neutrino emission is characterized by a luminosity and a duration that is typical for the signal expected from protoneutron stars and represents therefore a powerful source of neutrinos which could be possibly directly detected in case of events occurring close to our Galaxy. We discuss moreover possible connections between the birth of strange stars and explosive phenomena such as supernovae and gamma-ray-bursts.
The recent measurement of two solar mass pulsars has initiated an intense discussion on its impact on our understanding of the high-density matter in the cores of neutron stars. A task force meeting was held from October 7-10, 2013 at the Frankfurt Institute for Advanced Studies to address the presence of quark matter in these massive stars. During this meeting, the recent oservational astrophysical data and heavy-ion data was reviewed. The possibility of pure quark stars, hybrid stars and the nature of the QCD phase transition were discussed and their observational signals delineated.
Considering the finite IR behavior of quantum chromodynamics (QCD) running coupling constant in some experiments, we intend to investigate different models presenting running coupling with finite values in the IR region. Using analytic and background perturbation theories, we obtain some equation of states (EoSs) of strange quark matter which satisfy necessary conditions of suitable EoSs. Then we evaluate the properties of strange quark stars in general relativity. Our results for maximum gravitational mass is comparable with the recent LIGO data for the compact binary merger, GW190425.
Within the realms of the possibility of solid quark matter, we fitted the 500ks Chandra LETG/HRC data for RX J1856.5-3754 with a phenomenological spectral model, and found that electric conductivity of quark matter on the stellar surface is about > 1.2 x 10^{18} s^{-1}.
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