BONA FIDE, STRONG-VARIABLE GALACTIC LUMINOUS BLUE VARIABLE STARS ARE FAST ROTATORS: DETECTION OF A HIGH ROTATIONAL VELOCITY IN HR CARINAE
| Autor: | Roberto Claudio Gamen, D. J. Hillier, G. R. Solivella, E. Fernández-Lajús, Rodolfo H. Barbá, M. Teodoro, Augusto Damineli, A. P. Moisés, Jose H. Groh |
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| Rok vydání: | 2009 |
| Předmět: |
Stars: mass loss
Atmospheres Ciencias Astronómicas Stars: individual (HR Carinae) HR Carinae Rotation Variable stars Hertzsprung–Russell diagram Ciencias Físicas FOS: Physical sciences Astrophysics 01 natural sciences purl.org/becyt/ford/1 [https] symbols.namesake 0103 physical sciences atmospheres [Stars] Supergiant stars 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) Line (formation) Physics 010308 nuclear & particles physics Stars: rotation Astronomy and Astrophysics purl.org/becyt/ford/1.3 [https] Astrophysics - Astrophysics of Galaxies Stars variables: other [Stars] Astronomía rotation [Stars] Supernova Astrophysics - Solar and Stellar Astrophysics Stars: variables: other Supergiants Luminous blue variable 13. Climate action Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) symbols Stars: atmospheres Supergiant Variable star Mass loss mass loss [Stars] Instability strip CIENCIAS NATURALES Y EXACTAS individual (HR Carinae) [Stars] |
| Zdroj: | SEDICI (UNLP) Universidad Nacional de La Plata instacron:UNLP CONICET Digital (CONICET) Consejo Nacional de Investigaciones Científicas y Técnicas instacron:CONICET |
| ISSN: | 1538-4357 0004-637X |
| Popis: | 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 SiIV λλ4088-4116. To match their observed line profiles from 2009 May, a high rotational velocity of v rot ≃ 150 ∼ 20 km s-1 is needed (assuming an inclination angle of 30°), implying that HR Car rotates at ≃0.88 ∼ 0.2 of its critical velocity for breakup (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 v crit 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 v 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. Instituto de Astrofísica de La Plata Facultad de Ciencias Astronómicas y Geofísicas |
| Databáze: | OpenAIRE |
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