Related papers: Is Her X-1 a strange star?
In spite of the almost all-encompassing variability of Be stars, surveys play a steadily increasing role in complementing the insights gained from single-star studies. The definition of classical Be stars as recently augmented by…
Binaries are not always neatly aligned. Previous observations of the DI Her system showed that the spin axes of both stars are highly inclined with respect to one another and the orbital axis. Here we report on a measurement of the…
Aims. We aim to contribute to the identification of unassociated gamma-ray sources in the galactic plane in order to enlarge the currently known population of gamma-ray binaries and related systems, such as radio emitting X-ray binaries and…
A modified version of this paper is under process and with a new title and abstract. Hence, this version of the article is completely withdrawn.
A failed main-on in the 35d cycle of Her X-1 was observed with the Rossi X-Ray Timing Explorer (RXTE) on 1999 April 26. Exceptions to the normal 35d cycle have been seen only twice before; in 1983 and again 1993. We present timing and…
A few typos in Mamajek, Meyer, & Liebert (2002, AJ, 124, 1670) have been corrected in this erratum (including two stellar misidentifications and an incorrect power in the units of a slope). The most significant is the correction of a sign…
The existence of multiple anomalous U(1)s is demonstrated explicitly in a blow-up version of a heterotic Z_3 orbifold. Another blow-up of the same orbifold supports further evidence for the type-I/heterotic duality in four dimensions. It…
To enlarge our database of Chemically Peculiar (CP) stars, we compiled published data concerning the He-weak and He-rich stars observed by high-resolution spectroscopy techniques during last decades. Twenty He-weak and 28 He-rich stars have…
Motivated by recent suggestions that strange stars can be responsible for glitches and other observational features of pulsar, we review some possible equations of state and their implications for models of neutron, hybrid and strange…
Stars can be treated as self-gravitating fluid. Krori and Barua (1975) gave an analytical solutions to that kind of fluids. In this connection, we propose a de-Sitter model for an anisotropic strange star with the Krori-Barua spacetime. We…
A very short note, explaining the error in the original paper, which renders its central result incorrect.
During the last couple of years astronomers and astrophysicists have been debating on the fact whether the so called `strange stars' - stars made up of strange quark matter, have been discovered with the candidates like SAX J1808.4-3658, 4U…
The unique eclipsing, weak-lined T Tauri star KH 15D has been detected as an X-ray source in a 95.7 ks exposure from the Chandra X-ray Observatory archives. A maximum X-ray luminosity of 1.5 x 10^{29} erg s$^{-1}$ is derived in the 0.5--8…
In this article we address the mystery of dark matter. We expound the various evidences, astrophysical and cosmological, leading to hypothesize the existence of an invisible form of matter, whose attempts at detecting it have so far all…
Recent observations of hydrogen absorption that occurred when the first stars turned on may give insights into the nature of dark matter.
Inspection of the periodograms of TESS delta Scuti stars indicates that there is little, if any, similarity between the frequencies of stars in the same region of the H-R diagram. This is difficult to understand because pulsation models…
We present the results of a ROSAT Position Sensitive Proportional Counter observation of the variable radio star \ls. The source has a power law spectrum with photon index 1.1 +/- 0.3 and a luminosity of 5.9 x 10^{33} erg/s in the 0.1 -2.4…
It is suggested in this paper that the `bare' strange star might be not bare, and there could be a magnetosphere around it. As a strange star might be an intensely magnetized rotator, the induced unipolar electric field would be large…
The Blazhko effect in RR Lyrae stars is still poorly understood theoretically. Stars with multiple Blazhko periods or in which the Blazhko effect itself varies are particularly challenging. This study investigates the Blazhko effect in the…
Estimations of magnetic fields of neutron stars, observed as radio and X-ray pulsars, are discussed. It is shown, that theoretical and observational values for different types of radiopulsars are in good correspondence. Magnetic fields of…