Artículo
The enigmatic binary system HD 5980
Hillier, Desmond John; Koenigsberger, Gloria; Nazé, Yaël; Morrell, Nidia Irene
; Barbá, Rodolfo; Gamen, Roberto Claudio
Fecha de publicación:
19/03/2019
Editorial:
Wiley Blackwell Publishing, Inc
Revista:
Monthly Notices of the Royal Astronomical Society
ISSN:
0035-8711
Idioma:
Inglés
Tipo de recurso:
Artículo publicado
Clasificación temática:
Resumen
The Small Magellanic Cloud multiple system HD 5980 contains a luminous blue variable (LBV) that underwent a major eruption in 1994, and whose current spectrum is that of a hydrogen-rich Wolf-Rayet (WR) star. Since the eruption, the wind mass-loss rate has been declining while wind speeds have been steadily increasing. Observations obtained in 2014 when Star A (the LBV) eclipses Star B indicate that the fitted mass-loss rate and luminosity have reached the lowest values ever determined for such spectra: dot{M} = 4.5 × 10-5M_☉ yr^{-1}, L = 1.7 × 106 L☉. In addition, the radius of the LBV´s continuum-emitting region is similar to that derived from the eclipse light curves of the late 1970s. Hence, it appears to have attained a similar `low´ state to that of the late 1970s. While a good fit to the emission spectrum is obtained using a CMFGEN model, there are discrepancies in the UV. In particular, the extent of the observed absorption profiles is ̃1000 km s-1 greater than predicted by the emission-line intensities. Further, HST UV observations obtained in 2016, when Star A is eclipsed by Star B, show unusual P Cygni profiles that are not easily explained. Surprisingly the 2016 emission-line spectrum is similar to that at the opposite eclipse obtained in 2014. The complex UV profiles are likely to arise as a consequence of the dynamics of the wind-wind collision and radiative braking, both of which will cause significant departures from spherical symmetry, and have a strong orbital phase dependence. However, other scenarios, such as intrinsically aspherical winds, cannot be ruled out.
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Articulos(IALP)
Articulos de INST.DE ASTROFISICA LA PLATA
Articulos de INST.DE ASTROFISICA LA PLATA
Citación
Hillier, Desmond John; Koenigsberger, Gloria; Nazé, Yaël; Morrell, Nidia Irene; Barbá, Rodolfo; et al.; The enigmatic binary system HD 5980; Wiley Blackwell Publishing, Inc; Monthly Notices of the Royal Astronomical Society; 486; 1; 19-3-2019; 725-742
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