TY - JOUR
T1 - Kinematics and ultraviolet to infrared morphology of the inner Homunculus of η Carinae
AU - Smith, Nathan
AU - Morse, Jon A.
AU - Gull, Theodore R.
AU - Hillier, D. John
AU - Gehrz, Robert D
AU - Walborn, Nolan R.
AU - Bautista, Manuel
AU - Collins, Nicholas R.
AU - Corcoran, Michael F.
AU - Damineli, Augusto
AU - Hamann, Fred
AU - Hartman, Henrik
AU - Johansson, Sveneric
AU - Stahl, Otmar
AU - Weis, Kerstin
PY - 2004/4/10
Y1 - 2004/4/10
N2 - We present the first ultraviolet and optical images of η Car and its circumstellar Homunculus nebula, obtained with the Advanced Camera for Surveys/High Resolution Camera (ACS/HRC) on board the Hubble Space Telescope (HST). Compared to those at visual wavelengths, UV images reveal excess emission 0″.1-0.″6 from the central source along the minor axis that may emanate from the outer parts of η Car's nonspherical stellar wind, which dominates the UV flux from η Car. The UV emission fills the cavity inside a dust torus measured from infrared (IR) data; within 0″.2 of the star the UV emission projects a morphology reminiscent of the IR torus, but it is a factor of 10 smaller. This "little torus" seen in the UV may be related to the "Little Homunculus" discovered recently, signifying recurrent mass ejections with the same geometry. Finally, we reexamine the kinematics of nebular condensations near the star (Weigelt objects C and D) in HST images and spectra obtained over the past decade. We measure heliocentric velocities slower than previous estimates, and from proper motions we derive an ejection date of 1908 ± 12 yr, assuming linear motion. However, because of radiative acceleration, these objects may have been ejected earlier - perhaps during the 1890 outburst of η Car.
AB - We present the first ultraviolet and optical images of η Car and its circumstellar Homunculus nebula, obtained with the Advanced Camera for Surveys/High Resolution Camera (ACS/HRC) on board the Hubble Space Telescope (HST). Compared to those at visual wavelengths, UV images reveal excess emission 0″.1-0.″6 from the central source along the minor axis that may emanate from the outer parts of η Car's nonspherical stellar wind, which dominates the UV flux from η Car. The UV emission fills the cavity inside a dust torus measured from infrared (IR) data; within 0″.2 of the star the UV emission projects a morphology reminiscent of the IR torus, but it is a factor of 10 smaller. This "little torus" seen in the UV may be related to the "Little Homunculus" discovered recently, signifying recurrent mass ejections with the same geometry. Finally, we reexamine the kinematics of nebular condensations near the star (Weigelt objects C and D) in HST images and spectra obtained over the past decade. We measure heliocentric velocities slower than previous estimates, and from proper motions we derive an ejection date of 1908 ± 12 yr, assuming linear motion. However, because of radiative acceleration, these objects may have been ejected earlier - perhaps during the 1890 outburst of η Car.
KW - Circumstellar matter
KW - Stars: individual (η Carinae)
KW - Ultraviolet: stars
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U2 - 10.1086/382185
DO - 10.1086/382185
M3 - Article
AN - SCOPUS:2542510876
SN - 0004-637X
VL - 605
SP - 405
EP - 424
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1 I
ER -