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Three supergiant flares from soft γ-ray repeaters are observed, with typical released energy of ∼1044—47 erg. A conventional model (i.e. the magnetar model) for such events is catastrophic magnetism-powered instability through a magnetohydrodynamic process, in which a significant part of the short–hard γ-ray bursts could also be the result of magnetars. Based on various observational features (e.g. precession, glitches, thermal photon emission) and the underlying theory of strong interaction (quantum chromodynamics), it cannot yet be ruled out that pulsar-like stars might be actually solid quark stars. Strain energy develops during the life of a solid star, and starquakes could occur when stellar stresses reach a critical value, with a huge amount of energy released. An alternative model for supergiant flares of soft γ-ray repeaters is presented, in which the energy release during a starquake of a solid quark star is calculated. Numerical results for spherically asymmetric solid stars show that the gravitational energy released during a giant quake could be as high as 1048 erg if the tangential pressure is slightly higher than the radial one. Difficulties in magnetar models may be overcome if anomalous X-ray pulsars/soft γ-ray repeaters are accreting solid quark stars with mass ∼1—2M . [ABSTRACT FROM AUTHOR]

A unique transient bursting radio source, GCRT J1745−3009, has been discovered near the direction of the Galactic Centre. The explanation of this phenomenon is still an open question, although some efforts to understand its nature have been made. This Letter shows that most of the observed features can be reproduced by our proposed precessing pulsar model. It is found that the precession angle of the pulsar should be larger (≳15°) than that of previously known precessing pulsars, which have a precession angle ≲10°, if the beam width of the pulsar is larger than 10°. The pulsar could be a nulling (or even extremely nulling) radio pulsars to account for the transient nature of the source. This model can be confirmed if a pulsar is detected at the position of the source. The pulsar could hardly be a normal neutron star (but could probably be a solid quark star) if the spin period of the pulsar is detected to be ≳10 ms in the future. [ABSTRACT FROM AUTHOR]

The pulsar PSR B1828−11 has long-term, highly periodic and correlated variations in both pulse shape and the rate of slow-down. This phenomenon may provide evidence for the precession of the pulsar as suggested previously within the framework of free precession as well as forced. On a presumption of forced precession, we propose a quark planet model to this precession phenomenon instead, in which the pulsar is torqued by a quark planet. We construct this model by constraining the mass of the pulsar , the mass of the planet and the orbital radius of the planet . Five aspects are considered: the derived relation between and , the movement of the pulsar around the centre of mass, the ratio of and , the gravitational wave radiation time-scale of the planetary system, and the death-line criterion. We also calculate the range of the precession period derivative and the gravitational wave strength (at earth) permitted by the model. Under reasonable parameters, the observed phenomenon can be understood by a pulsar with a quark planet orbiting it. According to the calculations presented, the pulsar would be a quark star because of its low mass, which might eject a lump of quark matter (to become an orbiting planet) during its birth. [ABSTRACT FROM AUTHOR]