The supergiant B[e] star LHA 115-S 18 - binary and/or luminous blue variable?

Context. The mechanism by which supergiant (sg)B[e] stars support cool, dense dusty discs/tori and their physical relationship with other evolved, massive stars such as luminous blue variables is uncertain. Aims. In order to investigate both issues we have analysed the long term behaviour of the canonical sgB[e] star LHA 115-S 18. Methods. We employed the OGLE II-IV lightcurve to search for (a-)periodic variability and supplemented these data with new and historic spectroscopy. Results. In contrast to historical expectations for sgB[e] stars, S18 is both photometrically and spectroscopically highly variable. The lightcurve is characterised by rapid aperiodic ` aring' throughout the 16 years of observations. Changes in the high excitation emission line component of the spectrum imply evolution in the stellar temperature - as expected for luminous blue variables - although somewhat surprisingly, spectroscopic and photometric variability appears not to be correlated. Characterised by emission in low excitation metallic species, the cool circumstellar torus appears largely unaffected by this behaviour. Finally, in conjunction with intense, highly variable He ii emission, X-ray emission implies the presence of an unseen binary companion. Conclusions. S18 provides observational support for the putative physical association of (a subset of) sgB[e] stars and luminous blue variables. Given the nature of the circumstellar environment of S18 and that luminous blue variables have been suggested as SN progenitors, it is tempting to draw a parallel to the progenitors of SN1987A and SN2009ip. Moreover the likely binary nature of S18 strengthens the possibility that the dusty discs/tori that characterise sgB[e] stars are the result of binary-driven mass-loss; consequently such stars may provide a window on the short lived phase of mass-transfer in massive compact binaries.

Urban penalty: nuevas hipótesis y caso español (1860-1920)

El término urban penalty fue en principio utilizado para definir la sobremortalidad urbana durante la revolución industrial. Los antropómetras lo emplearon más tarde para definir un hecho simultáneo: el descenso de la estatura urbana con respecto a la rural. En la primera parte del trabajo proponemos tres nuevas hipótesis sobre ese castigo urbano: a) incorporar las aportaciones de la Teoría Económica sobre fallos de mercado al análisis de la sobremortalidad urbana; b) explicar la urban penalty mediante el modelo que Floud, Fogel, Harris y Chul Hong han elaborado recientemente para Gran Bretaña y c) sugerir respuestas a una pregunta que debe ser avalada o desmentida por investigaciones de ámbito municipal: ¿por qué los políticos españoles de la restauración tardaron décadas en acometer la reforma sanitaria de las ciudades? En la segunda parte del trabajo ofrecemos información que demuestra que España padeció sobremortalidad urbana derivada de fallos de mercado. Los datos de estatura rural y urbana evidencian por el contrario que, salvo excepciones, el país no experimentó urban penalty. El trabajo termina tratando de explicar esta particularidad y sosteniendo que el modelo de Floud, Fogel, Harris y Chul Hong puede aplicarse a esas excepciones.