TY - JOUR

T1 - He II λ4686 in η Carinae

T2 - collapse of the wind-wind collision region during periastron passage

AU - Teodoro, M.

AU - Damineli, A.

AU - Arias, J.I.

AU - Araujo, F.X. de

AU - Barba, R.H.

AU - Corcoran, M.F.

AU - Fernandes, M. Borges

AU - Fernandez-Lajus, E.

AU - Fraga, L.

AU - Gamen, R.C.

AU - Gonzalez, J. F.

AU - Groh, J. H.

AU - Marshall, J. L.

AU - McGregor, P. J.

AU - Morrell, N.

AU - Nicholls, D. C.

AU - Parkin, E. R.

AU - Pereira, C. B.

AU - Phillips, M. M.

AU - Solivella, G. R.

AU - Steiner, J. E.

AU - Stritzinger, Maximilian David

AU - Thompson, I.

AU - Torres, C. A. O.

AU - Torres, M. A. P.

AU - Zevallos Herencia, M. I.

PY - 2012

Y1 - 2012

N2 - The periodic spectroscopic events in eta Carinae are now well established and occur near the periastron passage of two massive stars in a very eccentric orbit. Several mechanisms have been proposed to explain the variations of different spectral features, such as an eclipse by the wind-wind collision (WWC) boundary, a shell ejection from the primary star or accretion of its wind onto the secondary. All of them have problems explaining all the observed phenomena. To better understand the nature of the cyclic events, we performed a dense monitoring of eta Carinae with five Southern telescopes during the 2009 low-excitation event, resulting in a set of data of unprecedented quality and sampling. The intrinsic luminosity of the He II lambda 4686 emission line (L similar to 310 L-circle dot) just before periastron reveals the presence of a very luminous transient source of extreme UV radiation emitted in the WWC region. Clumps in the primary's wind probably explain the flare-like behavior of both the X-ray and He II lambda 4686 light curves. After a short-lived minimum, He II lambda 4686 emission rises again to a new maximum, when X-rays are still absent or very weak. We interpret this as a collapse of the WWC onto the "surface" of the secondary star, switching off the hard X-ray source and diminishing the WWC shock cone. The recovery from this state is controlled by the momentum balance between the secondary's wind and the clumps in the primary's wind.

AB - The periodic spectroscopic events in eta Carinae are now well established and occur near the periastron passage of two massive stars in a very eccentric orbit. Several mechanisms have been proposed to explain the variations of different spectral features, such as an eclipse by the wind-wind collision (WWC) boundary, a shell ejection from the primary star or accretion of its wind onto the secondary. All of them have problems explaining all the observed phenomena. To better understand the nature of the cyclic events, we performed a dense monitoring of eta Carinae with five Southern telescopes during the 2009 low-excitation event, resulting in a set of data of unprecedented quality and sampling. The intrinsic luminosity of the He II lambda 4686 emission line (L similar to 310 L-circle dot) just before periastron reveals the presence of a very luminous transient source of extreme UV radiation emitted in the WWC region. Clumps in the primary's wind probably explain the flare-like behavior of both the X-ray and He II lambda 4686 light curves. After a short-lived minimum, He II lambda 4686 emission rises again to a new maximum, when X-rays are still absent or very weak. We interpret this as a collapse of the WWC onto the "surface" of the secondary star, switching off the hard X-ray source and diminishing the WWC shock cone. The recovery from this state is controlled by the momentum balance between the secondary's wind and the clumps in the primary's wind.

U2 - 10.1088/0004-637X/746/1/73

DO - 10.1088/0004-637X/746/1/73

M3 - Journal article

VL - 746

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

M1 - 73

ER -