Related papers: Interior Matter Estimates of Rapidly Rotating Comp…
One of the most important questions in the study of compact objects is the nature of pulsars, including whether they are composed of $\beta$-stable nuclear matter or strange quark matter. Observations of the newly discovered millisecond…
To constrain the equation of state of super-nuclear density matter and probe the interior composition of the X-ray pulsar in SAX J1808.4-3658. In our estimation, we consider both its persistent 2.49 ms X-ray pulsations discovered by…
Definitely, an affirmative answer to this question would have implications of fundamental importance for astrophysics (a new class of compact stars), and for the physics of strong interactions (deconfined phase of quark matter, and strange…
With the possible detection of the fastest spinning nuclear-powered pulsar XTE J1739-285 of frequency 1122 Hz (0.8913 ms), it arouses us to constrain the mass and radius of its central compact object and to imply the stellar matter…
The determination of mass and radius of a single neutron star EXO 0748-676 has been reported recently. Also, the estimate of radius from the measurement of moment of inertia of pulsar A in double pulsar system PSR J0737-3039 would be…
The interior of neutron stars contains nuclear matter at very high density for numerous subatomic particles compete with each other. Therefore, confirming the components and properties there is our significant task. Here we summarize the…
We show that r-mode instabilities severely constraint the composition of a compact star rotating at a submillisecond period. In particular, the only viable astrophysical scenario for such an object, present inside the Low Mass X-ray Binary…
The recent discovery of burst oscillations at 1122 Hz in the x-ray transient XTE J1739-285, together with the measurement of the mass of the binary millisecond pulsar PSR J0751+1807 (2.1 +- 0.2 solar masses) can finally allow us to put…
SAX J1808.4-3658 has a 2.5 millisecond neutron star rotation period and exhibits X-ray pulsations due to its rotating hot spot. Here we present an analysis of the pulse shapes of SAX J1808 during its 1998 outburst. The modeling of the pulse…
The accreting millisecond pulsar SAX J1808.4-3658 may be a transition object between accreting X-ray binaries and millisecond radio pulsars. We have constrained the thermal radiation from its surface through XMM-Newton X-ray observations,…
The recent discovery of burst oscillation at 1122Hz in the X-ray transient XTE J1739-285 supports the suggestion that it contains a submillisecond pulsar. In our estimations of the enormous dissipation effect in the transition boundary…
The optical counterpart of the binary millisecond X-ray pulsar SAX J1808.4-3658 during quiescence was detected at V = 21.5 mag by Homer et al. (2001). This star shows a 6% semi-amplitude sinusoidal modulation of its flux at the orbital…
The existence of the ultracompact object XTE J1814-338, with an inferred mass and radius of $M$ = 1.21 $\pm$ 0.05 $M_\odot$ and R = 7.0 $\pm$ 0.4 km, presents a great challenge for the theory of neutron stars. Within this context, we…
We suggest that the mass of four compact stars SAX J1808.4$-$3658, KS 1731$-$260, SAX J1750.8$-$2900 and IGR J17191$-$2821 can be determined from the difference in the observed kiloHertz quasi periodic oscillations (kHz QPO-s) of these…
Fast rotation of compact stars (at submillisecond period) and, in particular, their stability, are sensitive to the equation of state (EOS) of dense matter. Recent observations of XTE J1739-285 suggest that it contains a neutron star…
Recent observations of XTE J1739-285 suggest that it contains a neutron star rotating at 1122 Hz. Such rotational frequency would be the first for which the effects of rotation are significant. We study the consequences of very fast…
In this paper we present a coherent timing analysis of the 401 Hz pulsations of the accreting millisecond X-ray pulsar SAX J1808.4-3658 during its 2019 outburst. Using observations collected with the Neutron Star Interior Composition…
Millisecond radio pulsars are neutron stars that have been spun-up by the transfer of angular momentum during the low-mass X-ray binary phase. The transition from an accretion-powered to a rotation-powered pulsar takes place on evolutionary…
Compactness of some stars is explained if they are strange stars (SS) as shown by Dey et al. (1998) (D98) and Li et al. (1999a). One of these compact star candidates is the SAX J1808.4-3658 (SAX in short) believed to be an important link in…
We present a timing analysis of the 2015 outburst of the accreting millisecond X-ray pulsar SAX J1808.4-3658, using non-simultaneous XMM-Newton and NuStar observations. We estimate the pulsar spin frequency and update the system orbital…