IALP   13078
INSTITUTO DE ASTROFISICA LA PLATA
Unidad Ejecutora - UE
artículos
Título:
The Onfp Class in the Magellanic Clouds
Autor/es:
WALBORN, NOLAN R.; HOWARTH, IAN D.; EVANS, CHRISTOPHER J; CROWTHER, PAUL A.; MOFFAT, ANTHONY F. J.; ST-LOUIS, NICOLE; FARIÑA, CECILIA; BOSCH, GUILLERMO L.; MORRELL, NIDIA I.; BARBÁ, RODOLFO H.; VAN LOON, JACCO TH
Revista:
ASTRONOMICAL JOURNAL
Editorial:
IOP PUBLISHING LTD
Referencias:
Año: 2010 vol. 139 p. 1283 - 1294
ISSN:
0004-6256
Resumen:
The Onfp class of rotationally broadened, hot spectra was defined some
time ago in the Galaxy, where its membership to date numbers only eight.
The principal defining characteristic is a broad, centrally reversed He
II λ 4686 emission profile; other emission and absorption lines
are also rotationally broadened. Recent surveys in the Magellanic Clouds
(MCs) have brought the class membership there, including some related
spectra, to 28. We present a survey of the spectral morphology and
rotational velocities, as a first step toward elucidating the nature of
this class. Evolved, rapidly rotating hot stars are not expected
theoretically, because the stellar winds should brake the rotation.
Luminosity classification of these spectra is not possible, because the
principal criterion (He II λ4686) is peculiar; however, the MCs
provide reliable absolute magnitudes, which show that they span the
entire range from dwarfs to supergiants. The Onfp line-broadening
distribution is distinct and shifted toward larger values from those of
normal O dwarfs and supergiants with >99.99% confidence. All cases
with multiple observations show line-profile variations, which even
remove some objects from the class temporarily. Some of them are
spectroscopic binaries; it is possible that the peculiar profiles may
have multiple causes among different objects. The origin and future of
these stars are intriguing; for instance, they could be stellar mergers
and/or gamma-ray-burst progenitors.