BONA FIDE, STRONG-VARIABLE GALACTIC LUMINOUS BLUE VARIABLE STARS ARE FAST ROTATORS: DETECTION OF A HIGH ROTATIONAL VELOCITY IN HR CARINAE

We report optical observations of the luminous blue variable (LBV) HR Carinae which show that the star has reached a visual minimum phase in 2009. More importantly, we detected absorptions due to Si lambda lambda 4088-4116. To match their observed line profiles from 2009 May, a high rotational velocity of nu(rot) similar or equal to 150 +/- 20 km s(-1) is needed (assuming an inclination angle of 30 degrees), implying that HR Car rotates at similar or equal to 0.88 +/- 0.2 of its critical velocity for breakup (nu(crit)). Our results suggest that fast rotation is typical in all strong-variable, bona fide galactic LBVs, which present S-Dor-type variability. Strong-variable LBVs are located in a well-defined region of the HR diagram during visual minimum (the ""LBV minimum instability strip""). We suggest this region corresponds to where nu(crit) is reached. To the left of this strip, a forbidden zone with nu(rot)/nu(crit) > 1 is present, explaining why no LBVs are detected in this zone. Since dormant/ex LBVs like P Cygni and HD 168625 have low nu(rot), we propose that LBVs can be separated into two groups: fast-rotating, strong-variable stars showing S-Dor cycles (such as AG Car and HR Car) and slow-rotating stars with much less variability (such as P Cygni and HD 168625). We speculate that supernova (SN) progenitors which had S-Dor cycles before exploding (such as in SN 2001ig, SN 2003bg, and SN 2005gj) could have been fast rotators. We suggest that the potential difficulty of fast-rotating Galactic LBVs to lose angular momentum is additional evidence that such stars could explode during the LBV phase.

Caciquisme rural i contrautopies pageses. Testimonis d'unes cobles de la Conca de Barberà i del Priorat

Aquest article presenta i estudia un conjunt de cobles de la tradició oral recollides a la Conca de Barberà i al Priorat. Les cançons, creades en el marc de la Restauració, denuncien un conjunt de greuges lligats al caciquisme i al desenvolupament de l’Estat i de les relacions capitalistes que aquest fomenta. Les cobles presenten dos grans registres expressius, que obeeixen a diferents perspectives dels greuges que denuncien. D’una banda tenim unes cobles caracteritzades per una sàtira violenta, dreturera, una sintaxi cantelluda, antítesis primàries, i un recurs viu a les deformacions de l’adversari. En aquests casos, les lletres obeeixen a factors percebuts en la immediatesa de la comunitat, d’acord amb una perspectiva tradicional. D’altra banda, tenim cobles que es caracteritzen per un relaxament còmic i jocós de la sàtira, per una major narrativitat o arromançament, i també per una catarsi benèfica. En aquests casos, les cançons responen a un nou ordre de factors —polítics/política de partit, representants de l’Estat, noves modes estètiques, etc.— que en la societat rural, especialment entre aquells sectors poc introduïts a la modernitat, són percebuts amb una amplitud panoràmica, d’acord amb una ingenuïtat perceptiva, amb un distanciament naïf cap a la realitat. Es tracta d’un ordre de percepcions que informen els trets expressius que hem apuntat quant a aquestes cobles. Unes manifestacions ben il·lustratives d’aquestes darreres composicions són unes contrautopies que recullen, amb voluntat de totalitat, el conjunt d’abusos que pateix la societat pagesa, general o local.

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He II lambda 4686 IN eta CARINAE: COLLAPSE OF THE WIND-WIND COLLISION REGION DURING PERIASTRON PASSAGE

The periodic spectroscopic events in eta Carinae are now well established and occur near the periastron passage of two massive stars in a very eccentric orbit. Several mechanisms have been proposed to explain the variations of different spectral features, such as an eclipse by the wind-wind collision (WWC) boundary, a shell ejection from the primary star or accretion of its wind onto the secondary. All of them have problems explaining all the observed phenomena. To better understand the nature of the cyclic events, we performed a dense monitoring of eta Carinae with five Southern telescopes during the 2009 low-excitation event, resulting in a set of data of unprecedented quality and sampling. The intrinsic luminosity of the He II lambda 4686 emission line (L similar to 310 L-circle dot) just before periastron reveals the presence of a very luminous transient source of extreme UV radiation emitted in the WWC region. Clumps in the primary's wind probably explain the flare-like behavior of both the X-ray and He II lambda 4686 light curves. After a short-lived minimum, He II lambda 4686 emission rises again to a new maximum, when X-rays are still absent or very weak. We interpret this as a collapse of the WWC onto the "surface" of the secondary star, switching off the hard X-ray source and diminishing the WWC shock cone. The recovery from this state is controlled by the momentum balance between the secondary's wind and the clumps in the primary's wind.