ABSTRACT
The planetary nebula stage is the ultimate fate of stars with masses one to eight times that of the Sun (M(â)). The origin of their complex morphologies is poorly understood, although several mechanisms involving binary interaction have been proposed. In close binary systems, the orbital separation is short enough for the primary star to overfill its Roche lobe as the star expands during the asymptotic giant branch phase. The excess gas eventually forms a common envelope surrounding both stars. Drag forces then result in the envelope being ejected into a bipolar planetary nebula whose equator is coincident with the orbital plane of the system. Systems in which both stars have ejected their envelopes and are evolving towards the white dwarf stage are said to be double degenerate. Here we report that Henize 2-428 has a double-degenerate core with a combined mass of â¼1.76M(â), which is above the Chandrasekhar limit (the maximum mass of a stable white dwarf) of 1.4M(â). This, together with its short orbital period (4.2 hours), suggests that the system should merge in 700 million years, triggering a type Ia supernova event. This supports the hypothesis of the double-degenerate, super-Chandrasekhar evolutionary pathway for the formation of type Ia supernovae.
ABSTRACT
El linfoma tiroideo es una enfermedad rara, que supone menos del 2% de las neoplasias de tiroides. Presentamos el caso de una paciente diagnosticada tras la aparición de una masa tiroidea de crecimiento rápido, en quien existía una historia previa de una tiroiditis crónica autoinmunitaria. El tratamiento suele ser quirúrgico, asociado a quimioterapia y/o radioterapia, y su pronóstico y su evolución dependen del grado de extensión del tumor al diagnóstico
Thyroid lymphoma is a rare disease, representing less than 2% of all malignant tumors of the thyroid. We report the case of a patient with a past history of chronic autoimmune thyroiditis who was diagnosed after developing a rapidly growing thyroid mass. Treatment is usually surgical, associated with chemotherapy and/or radiotherapy. The prognosis and follow-up depend on the stage of the tumor at presentation
