Artículos de revistas
Bona-fide, strong-variable galactic Luminous Blue Variable stars are fast rotators: detection of a high rotational velocity in HR Carinae
Fecha
2009-12Registro en:
Groh, J. H.; Damineli, A.; Hillier, D. J.; Barba, Rodolfo Hector; Fernandez Lajus, Eduardo Eusebio; et al.; Bona-fide, strong-variable galactic Luminous Blue Variable stars are fast rotators: detection of a high rotational velocity in HR Carinae; IOP Publishing; Astrophysical Journal; 705; 12-2009; 25-30
0004-637X
CONICET Digital
CONICET
Autor
Groh, J. H.
Damineli, A.
Hillier, D. J.
Barba, Rodolfo Hector
Fernandez Lajus, Eduardo Eusebio
Gamen, Roberto Claudio
Moisés, A. P.
Solivella, Gladys Rebeca
Teodoro, M.
Resumen
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 IV 4088-4116 Angstroms. To match their observed line profiles from 2009 May, a high rotational velocity of vrot=150 +- 20 km/s is needed (assuming an inclination angle of 30 degrees), implying that HR Car rotates at ~0.88 +- 0.2 of its critical velocity for break-up (vcrit). 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 vcrit is reached. To the left of this strip, a forbidden zone with vrot/vcrit>1 is present, explaining why no LBVs are detected in this zone. Since dormant/ex LBVs like P Cygni and HD 168625 have low vrot, we propose that LBVs can be separated in 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 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 an additional evidence that such stars could explode during the LBV phase.