EVOLUTIONARY TRAJECTORIES OF ULTRACOMPACT "BLACK WIDOW" PULSARS WITH VERY LOW MASS COMPANIONS

The existence of millisecond pulsars with planet-mass companions in close orbits is challenging from the stellar evolution point of view. We calculate in detail the evolution of binary systems self-consistently, including mass transfer, evaporation, and irradiation of the donor by X-ray feedback, demonstrating the existence of a new evolutionary path leading to short periods and compact donors as required by the observations of PSR J1719-1438. We also point out the alternative of an exotic nature of the companion planet-mass star.

Cochleovestibular nerve involvement in multifocal fibrosclerosis

Objectives: To report a case of multifocal fibrosclerosis with a nine-year follow up, and to discuss this disease's radiological appearance and management. The disease is a rare systemic disorder of unknown cause characterised by fibrous proliferation involving multiple anatomical sites. Case report: A 50-year-old woman presented with histological findings characterised by similar inflammatory processes involving the meninges, pituitary gland, peritoneum, retroperitoneum and orbits, prompting a search for a common pathophysiology. A diagnosis of multifocal fibrosclerosis was postulated. Symptom improvement was noted after treatment with prednisone and azathioprine. Conclusion: This is the first documented case of involvement of the cochleovestibular nerve in a patient with multifocal fibrosclerosis. The rare association between fibrotic diseases and masses showing various clinical patterns should be kept in mind by otolaryngologists, and imaging performed to investigate for multifocal fibrosclerosis. However, diagnosis can only be confirmed with tissue biopsy and histopathological examination.

Transiting exoplanets from the CoRoT space mission XX. CoRoT-20b: A very high density, high eccentricity transiting giant planet

We report the discovery by the CoRoT space mission of a new giant planet, CoRoT-20b. The planet has a mass of 4.24 +/- 0.23 M-Jup and a radius of 0.84 +/- 0.04 R-Jup. With a mean density of 8.87 +/- 1.10 g cm(-3), it is among the most compact planets known so far. Evolutionary models for the planet suggest a mass of heavy elements of the order of 800 M-circle plus if embedded in a central core, requiring a revision either of the planet formation models or both planet evolution and structure models. We note however that smaller amounts of heavy elements are expected by more realistic models in which they are mixed throughout the envelope. The planet orbits a G-type star with an orbital period of 9.24 days and an eccentricity of 0.56. The star's projected rotational velocity is v sin i = 4.5 +/- 1.0 km s(-1), corresponding to a spin period of 11.5 +/- 3.1 days if its axis of rotation is perpendicular to the orbital plane. In the framework of Darwinian theories and neglecting stellar magnetic breaking, we calculate the tidal evolution of the system and show that CoRoT-20b is presently one of the very few Darwin-stable planets that is evolving toward a triple synchronous state with equality of the orbital, planetary and stellar spin periods.

Surgical treatment of globe subluxation in the active phase of the myogenic type of Graves orbitopathy: case reports

The purpose of the present article is to present and discuss two cases of globe subluxation in the active phase of myogenic Graves' orbitopathy and to evaluate the prevalence of this phenomenon. Two patients with the myogenic variant of Graves' orbitopathy that had being treated with oral and intravenous steroid pulses developed globe subluxation. Both had to have urgent eyelid and orbital decompression. After these observations, we reviewed the medical records of a sample of 284 patients (482 orbits) who had had orbital decompression at our Institution from 1992 to 2010, with a search for cases presenting severe proptosis or globe subluxation in the active phase of myogenic Graves' orbitopathy. No patient had to have decompression for globe subluxation in the active phase of Graves' orbitopathy. The prevalence of this event as an indication for surgery in the myogenic variant of Graves' orbitopathy was therefore 0.7% (2/284) or even less. The combination of lowering the upper eyelid and orbital decompression had a dramatic therapeutic effect on these patients despite the presence of intense inflammatory signs in the orbits. In conclusion, patients affected with the myogenic variant of Graves' orbitopathy may develop globe subluxation. Urgent surgical treatments should not be postponed despite the presence of active inflammation.

Stability and dynamics of terrestrial planets in binary star systems: application on Alpha Centauri

Binary stars are frequent in the universe, with about 50% of the known main sequence stars being located at a multiple star system (Abt, 1979). Even though, they are universally thought as second rate sites for the location of exo-planets and the habitable zone, due to the difficulties of detection and high perturbation that could prevent planet formation and long term stability. In this work we show that planets in binary star systems can have regular orbits and remain on the habitable zone. We introduce a stability criterium based on the solution of the restricted three body problem and apply it to describe the short period planar and three-dimentional stability zones of S-type orbits around each star of the Alpha Centauri system. We develop as well a semi-analytical secular model to study the long term dynamics of fictional planets in the habitable zone of those stars and we verify that planets on the habitable zone would be in regular orbits with any eccentricity and with inclination to the binary orbital plane up until 35 degrees. We show as well that the short period oscillations on the semi-major axis is 100 times greater than the Earth's, but at all the time the planet would still be found inside the Habitable zone.

A Galactic ring of minimum stellar density near the solar orbit radius

We analyse the secular effects of a long-lived Galactic spiral structure on the stellar orbits with mean radii close to the corotation resonance. By test-particle simulations and different spiral potential models with parameters constrained on observations, we verified the formation of a minimum with amplitude ∼30–40 per cent of the background disc stellar density at corotation. Such a minimum is formed by the secular angular momentum transfer between stars and the spiral density wave on both sides of corotation. We demonstrate that the secular loss (gain) of angular momentum and decrease (increase) of mean orbital radius of stars just inside (outside) corotation can counterbalance the opposite trend of exchange of angular momentum shown by stars orbiting the librational points L4/5 at the corotation circle. Such secular processes actually allow steady spiral waves to promote radial migration across corotation. We propose some pieces of observational evidence for the minimum stellar density in the Galactic disc, such as its direct relation to the minimum in the observed rotation curve of the Galaxy at the radius r ∼ 9 kpc (for R0 = 7.5 kpc), as well as its association with a minimum in the distribution of Galactic radii of a sample of open clusters older than 1Gyr. The closeness of the solar orbit adius to the corotation resonance implies that the solar orbit lies inside a ring of minimum surface density (stellar + gas). This also implies a correction to larger values for the estimated total mass of the Galactic disc, and consequently, a greater contribution of the disc componente to the inner rotation curve of the Galaxy.