Related papers: PSR B1257+12: a quark star with planets?
The core accretion theory of planetary formation does not predict that super-Jupiters will form beyond the snow line of a low mass stars. We present a discovery of 3.9 +- 1.2 M_Jup mass planet orbiting the 0.59 +- 0.17 M_Sun star using the…
The recent observation of the pulsar PSR J1614-2230 with a mass of 1.97 +/- 0.04 M_sun gives a strong constraint on the quark and nuclear matter equations of state (EoS). We explore the parameter ranges for a parameterized EoS for quark…
Extended very-high-energy $\gamma$-ray emission from middle-aged pulsars as revealed recently by several groundbased $\gamma$-ray experiments has strong implication on the transport of high-energy particles in the interstellar medium…
The nature of the 5-12 s "anomalous" X-ray pulsars remains a mystery. Among the models that have been proposed to explain the properties of AXPs, the most likely ones are: (1) isolated accreting neutron stars evolved from the…
PSR J1829+2456 is a radio pulsar in a relativistic binary system with another neutron star. It has a rotational period of 41 ms and a mildly eccentric ($e = 0.14$) 28-hr orbit. We have continued its observations with the Arecibo radio…
We have obtained images of the eclipsing pulsar binary PSR~B1957+20 using the Planetary Camera of the Hubble Space Telescope. The high spatial resolution of this instrument has allowed us to separate the pulsar system from a nearby…
Using the Color-Dielectric model to describe quark confinement, including strange quarks and accounting for beta--equilibrium, we get masses for a static neutron star in the range $1.3\leq M/M_{\odot}\leq 1.54 $ for a radius $R\approx 9$…
We present new parallax measurements from the CFHT Infrared Parallax Program and the Pan-STARRS 3$\pi$ Steradian Survey for the young ($\approx150-300$ Myr) triple system VHS J125601.92$-$125723.9. This system is composed of a nearly…
Recent timing observations of the double pulsar J0737-3039A/B have shown that its transverse velocity is extremely low, only 10 km/s, and nearly in the Plane of the Galaxy. With this new information, we rigorously re-examine the history and…
We detected a nearby (d=360 pc), old (5 Myr) pulsar B1133+16 with Chandra. The observed pulsar's flux is $(0.8\pm 0.2)\times 10^{-14}$ ergs cm$^{-2}$ s$^{-1}$ in the 0.5-8 keV band. Because of the small number of counts detected, the…
RR Lyrae pulsating stars have been extensively used as tracers of old stellar populations for the purpose of determining the ages of galaxies, and as tools to measure distances to nearby galaxies. There was accordingly considerable interest…
I introduce the two classes of pulsar, white-dwarf binaries, and describe for each what we have learned from a specific system, PSR J1012+5307 and PSR B0655+64, respectively, summarising what has been done, presenting new results, and…
A transiting planetary system was discovered independently by two groups, under the names WASP-86 (Faedi et al. 2016) and KELT-12 (Stevens et al. 2017). The properties of the system determined in these works were very different, most…
Based on observational facts and a variety of theoretical arguments we discuss in this work the possibility that pulsars in Low-Mass Binary Pulsar systems could be strange stars rather than neutron stars. It is shown that, although subject…
The possible existence of two families of compact stars, neutron stars and quark stars, naturally leads to a scenario in which a conversion process between the two stellar objects occurs with a consequent release of energy of the order of…
We develop a general method for analyzing the light curves of microlensed quasars and apply it to the OGLE light curves of the four-image lens Q2237+0305. We simultaneously estimate the effective source velocity, the average stellar mass,…
(abridged) Gamma-ray binaries are massive stars with compact object companions that are observed to emit most of their energy in the gamma-ray range. One of these binaries is known to contain a radio pulsar, PSR B1259-63. Synchrotron and…
Models of M-type Miras with masses of 1 $M_\odot$ and 1.2 $M_\odot$, i.e. with envelope masses of about 0.4 $M_\odot$ and 0.6 $M_\odot$, have been constructed, and a comparison has been made of their observable properties. Geometric…
The structure of a spherically symmetric stable dark 'star' is discussed, at zero temperature, containing 1) a core of quarks in the deconfined phase and antileptons 2) a shell of hadrons in particular $n$, $p$, $\Lambda$ and $\Sigma^-$ and…
Recent measurement of a high millisecond pulsar mass (PSR J1614-2230, 1.97+-0.04 Msun) compared with the low mass of PSR J0751+1807 (1.26+-0.14 Msun) indicates a large span of masses of recycled pulsars and suggests a broad range of neutron…