Evidence for strange stars from joint observation of harmonic absorption bands and of redshift

Abstract

From recent reports on terrestrial heavy ion collision experiments it appears that one may not obtain information about the existence of asymptotic freedom (AF) and chiral symmetry restoration (CSR) for quarks of QCD at high density. This information may still be obtained from compact stars -if they are made up of strange quark matter (SQM).Very high gravitational redshift lines (GRL), seen from some compact stars, seem to suggest high ratios of mass and radius (M/R) for them. This is suggestive of strange stars (SS) and can in fact be fitted very well with SQM equation of state (EOS) deduced with built in AF and CSR. In some other stars broad absorption bands (BAB) appear at about ∼0.3 keV and multiples thereof, that may fit in very well with resonance with harmonic compressional breathing mode frequencies of these SS. Emission at these frequencies are also observed in six stars.If these two features of large GRL and BAB were observed together in a single star, it would strengthen the possibility for the existence of SS in nature and would vindicate the current dogma of AF and CSR that we believe in QCD. Recently, in 4U 1700 − 24, both features appear to be detected, which may well be interpreted as observation of SS -although the group that analyzed the data did not observe this possibility. We predict that if the shifted lines, that has been observed, are from neon with GRL shift z = 0.4 -then the compact object emitting it is a SS of mass 1.2 M and radius 7 km. In addition the fit to the spectrum leaves a residual with broad dips at 0.35 keV and multiples thereof, as in 1E 1207 − 5209 which is again suggestive of SS.

Measurement of neutron star parameters: A review of methods for low-mass X-ray binaries

“…Therefore, it is required to accurately measure at least three independent global parameters of the same neutron star in order to constrain the EoS models, and hence to understand the supranuclear core matter. This is also true for the EoS models of strange matter (made of u, d and s quarks; Witten (1984); Farhi and Jaffe (1984); Bombaci (1997); Bombaci et al (2000); Bhattacharyya et al (2001c); Bagchi et al (2006)). However, some neutron star EoS models can be ruled out only by mass measurement.…”

X-ray views of neutron star low-mass X-ray binaries

“…The dense core of a neutron star may contain pion condensates, deconfined quarks, or other exotic (and possibly unknown) forms of matter, which makes the study of this part of the star extremely interesting. Moreover according to a model, some of the neutron stars are actually "strange stars" made entirely of u, d and s quarks [8]. Unfortunately, in spite of many theoretical studies, the properties of matter in the core of a neutron star is not yet known, because such a dense degenerate matter cannot be created in the laboratory.…”

Analyzing Hadron-Quark Matter Phase Transition by Macroscopic Properties of Neutron Stars

“…The exemplaries are EXO 0748-676, 4U 1700+24, 1E1207-5209 and RX J1856.5-3574. 3,4 We are completely aware of the fact that an conclusive characterization of the chemical composition of those stars is out of reach so far, nevertheless there does exist the possibility to extract some constraints on a possible hadron-quark phase transition.…”