The swallowing of a quark star by a black hole

We describe a model within the "quark-nova" scenario to interpret the recent observations of early X-ray afterglows of long gamma-ray bursts (GRBs) with the Swift satellite. This is a three-stage model within the context of a core-collapse supernova. STAGE 1 is an accreting (proto-) neutron star leading to a possible delay between the core collapse and the GRB. STAGE 2 is accretion onto a quark star, launching an ultrarelativistic jet generating the prompt GRB. This jet also creates the afterglow as the jet interacts with the surrounding medium creating an external shock. Slower shells ejected from the quark star (during accretion), can re-energize the external shock leading to a flatter segment in the X-ray afterglow. STAGE 3, which occurs only if the quark star collapses to form a black hole, consists of an accreting black hole. The jet launched in this accretion process interacts with the preceding quark star jet, and could generate the flaring activity frequently seen in early X-ray afterglows. Alternatively, a STAGE 2b can occur in our model if the quark star does not collapse to a black hole. The quark star in this case can then spin down due to magnetic braking, and the spin down energy may lead to flattening in the X-ray afterglow as well. This model seems to account for both the energies and the timescales of GRBs, in addition to the newly discovered early X-ray afterglow features.

Download Full-text

QCD — MOTIVATED QUARK STARS IN THE LIGHT OF RECENT ASTROPHYSICAL OBSERVATIONS

International Journal of Modern Physics B ◽

10.1142/s0217979200001102 ◽

2000 ◽

Vol 14 (19n20) ◽

pp. 1939-1952

Author(s):

MIRA DEY ◽

IGNAZIO BOMBACI ◽

JISHNU DEY ◽

SUBHARTHI RAY ◽

E. P. J. VAN DEN HEUVEL ◽

...

Keyword(s):

Black Hole ◽

Gamma Ray ◽

Observational Evidence ◽

Gamma Ray Bursts ◽

Compact Objects ◽

The Other ◽

Quark Star ◽

Burst Source ◽

X Ray ◽

Quark Stars

Are there quark stars in nature? We review the question in the light of modern astrophysical observations. Quark stars have properties which are very similar to those of neutron stars. For example they are now known to have the same kind of cooling properties. Their masses may also be similar. On the other hand, gamma ray bursts (GRB), the brightest phenomenon observable at present in the sky, could possibly be conversion of normal or neutron matter on the surface of a quark star. The best observational evidence for the existence of quark stars seems to be some compact objects, the X-Ray burst source 4U 1820-30, the X-ray pulsar Her X-1, the star 4U 1728-34 and SAX J-1808.4-3658, this last one being the stablest and fastest rotating hard X-ray pulsar known to date. The mass of at least these four objects is high and their radius is low, placing them close to the black hole line, in the mass–radius (M–R) plot.

Download Full-text