Fast Pulsars, Strange Stars: An Opportunity in Radio Astronomy

Abstract

The world's data on radio pulsars are not expected to represent the underlying pulsar population because of a search bias against detection of short periods, especially below 1 ms. Yet pulsars in increasing numbers with periods right down to this limit have been discovered, suggesting that there may be even shorter ones. If pulsars with periods below 1/2 ms were found, the conclusion that the confined hadronic phase of nucleons and nuclei is only metastable would be almost inescapable. The plausible ground state in that event is the deconfined phase of (3-flavor) strange-quark-matter. From the QCD energy scale this is as likely a ground state as the confined phase. We show that strange matter as the ground state is not ruled out by any known fact, and most especially not by the fact that the universe is in the confined phase.

Limiting rotational period of neutron stars

“…The only general category of stars that could have smaller rotation periods than neutron stars is the category of stars that are made of hypothetical matter that is stable and self-bound in bulk at sufficiently high equilibrium energy density [22,23]. The connection of the limiting rotational period of a star composed of matter that is self-bound (p = 0) at the equilibrium energy density, fe, is trivial to establish.…”

Limiting Rotational Period of Neutron Stars

“…Several recent accounts of the subject can be found in Ref. [22,41]. Another candidate in the category of self-bound stars are so called Q-stars [42,43].…”

“…':t;'he high density required of neutron star models (see Fig. 3) if they are to withstand short rotational periods has been cited as reason enough to suspect that short period pulsars, if they exist, are not neutron stars [21,22].…”

From quark stars to hybrid stars

“…The latter consists of an approximately equal number of up, down and strange quarks having energy per baryon E/A smaller than that of iron (E F e ≈ 930 MeV), at zero temperature and pressure [10]. Stars entirely composed of matter in such ultra-stable state are self-bound [11,12] and could rotate with a period well below one millisecond [13,14].A possible problem in interpreting neutron stars as strange quark stars is the difficulty of having glitches in the latter, since the most widely accepted model for the glitches require the existence of a crystallized phase trapping magnetic …”