The luminous eclipsing SMC OB + WN binary HD 5980 before and during the recent LBV-like outburst: An extreme case of colliding winds

The 1994 LBV-(luminous blue variable)like outburst of one of the luminous, hot components of the binary HD 5980 made it the brightest star in the Small Magellanic Cloud for an interval of 5 months. The most intriguing question to arise from this event is the following: Why did the HD 5980 spectrum c...

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Detalles Bibliográficos
Publicado: 1998
Materias:
Stars: Binaries: Eclipsing
Stars: Individual: HD 5980
Stars: Mass loss
Stars: Variables
Stars: Wolf-Ravet
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v497_n2PARTI_p896_Moffat
http://hdl.handle.net/20.500.12110/paper_0004637X_v497_n2PARTI_p896_Moffat
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_0004637X_v497_n2PARTI_p896_Moffat
record_format dspace
spelling paper:paper_0004637X_v497_n2PARTI_p896_Moffat2023-06-08T14:28:39Z The luminous eclipsing SMC OB + WN binary HD 5980 before and during the recent LBV-like outburst: An extreme case of colliding winds Stars: Binaries: Eclipsing Stars: Individual: HD 5980 Stars: Mass loss Stars: Variables Stars: Wolf-Ravet The 1994 LBV-(luminous blue variable)like outburst of one of the luminous, hot components of the binary HD 5980 made it the brightest star in the Small Magellanic Cloud for an interval of 5 months. The most intriguing question to arise from this event is the following: Why did the HD 5980 spectrum change from an H-poor WN3 with veiled OB absorption lines about 20 yr ago to an H-rich WN11 without central absorption lines during the outburst? In an attempt to answer this apparent enigma, we present and analyze new phase-dependent spectroscopic, polarimetric, and light-curve observations. Together with other published data, these new observations allow us to improve the orbital parameters considerably, except for the radial velocity amplitudes and hence the masses, which are only roughly constrained. Especially important in HD 5980 is the strong collision of the two nearly equal pre-outburst winds. The emission-line spectrum generated by the collision tends to mask the underlying line spectra of both components when the system is relatively quiescent. We argue that the pre-erupting system consists of a very luminous but moderately massive H-rich O type supergiant, possibly with emission lines, and a low-mass, H-poor, relatively faint WN companion, whose lines are mostly drowned out by wind collision emission, the spectrum of which largely imitates that of a WNE star. It was the O supergiant that erupted in a normal way as an H-rich, visually bright WN11 star. In this way, the need for peculiar evolutionary scenarios (e.g., rapid evolution from a faint, low-mass, H-poor WNE star to a luminous, H-rich WNL star) is avoided. © 1998. The American Astronomical Society. All rights reserved. 1998 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v497_n2PARTI_p896_Moffat http://hdl.handle.net/20.500.12110/paper_0004637X_v497_n2PARTI_p896_Moffat
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Stars: Binaries: Eclipsing
Stars: Individual: HD 5980
Stars: Mass loss
Stars: Variables
Stars: Wolf-Ravet
spellingShingle Stars: Binaries: Eclipsing
Stars: Individual: HD 5980
Stars: Mass loss
Stars: Variables
Stars: Wolf-Ravet
The luminous eclipsing SMC OB + WN binary HD 5980 before and during the recent LBV-like outburst: An extreme case of colliding winds
topic_facet Stars: Binaries: Eclipsing
Stars: Individual: HD 5980
Stars: Mass loss
Stars: Variables
Stars: Wolf-Ravet
description The 1994 LBV-(luminous blue variable)like outburst of one of the luminous, hot components of the binary HD 5980 made it the brightest star in the Small Magellanic Cloud for an interval of 5 months. The most intriguing question to arise from this event is the following: Why did the HD 5980 spectrum change from an H-poor WN3 with veiled OB absorption lines about 20 yr ago to an H-rich WN11 without central absorption lines during the outburst? In an attempt to answer this apparent enigma, we present and analyze new phase-dependent spectroscopic, polarimetric, and light-curve observations. Together with other published data, these new observations allow us to improve the orbital parameters considerably, except for the radial velocity amplitudes and hence the masses, which are only roughly constrained. Especially important in HD 5980 is the strong collision of the two nearly equal pre-outburst winds. The emission-line spectrum generated by the collision tends to mask the underlying line spectra of both components when the system is relatively quiescent. We argue that the pre-erupting system consists of a very luminous but moderately massive H-rich O type supergiant, possibly with emission lines, and a low-mass, H-poor, relatively faint WN companion, whose lines are mostly drowned out by wind collision emission, the spectrum of which largely imitates that of a WNE star. It was the O supergiant that erupted in a normal way as an H-rich, visually bright WN11 star. In this way, the need for peculiar evolutionary scenarios (e.g., rapid evolution from a faint, low-mass, H-poor WNE star to a luminous, H-rich WNL star) is avoided. © 1998. The American Astronomical Society. All rights reserved.
title The luminous eclipsing SMC OB + WN binary HD 5980 before and during the recent LBV-like outburst: An extreme case of colliding winds
title_short The luminous eclipsing SMC OB + WN binary HD 5980 before and during the recent LBV-like outburst: An extreme case of colliding winds
title_full The luminous eclipsing SMC OB + WN binary HD 5980 before and during the recent LBV-like outburst: An extreme case of colliding winds
title_fullStr The luminous eclipsing SMC OB + WN binary HD 5980 before and during the recent LBV-like outburst: An extreme case of colliding winds
title_full_unstemmed The luminous eclipsing SMC OB + WN binary HD 5980 before and during the recent LBV-like outburst: An extreme case of colliding winds
title_sort luminous eclipsing smc ob + wn binary hd 5980 before and during the recent lbv-like outburst: an extreme case of colliding winds
publishDate 1998
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v497_n2PARTI_p896_Moffat
http://hdl.handle.net/20.500.12110/paper_0004637X_v497_n2PARTI_p896_Moffat
_version_ 1768545534431199232

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