A moderately precise dynamical age for the Homunculus of Eta Carinae based on 13 years of HST imaging

Abstract

The HST archive contains a large collection of images of eta Carinae, and this paper analyzes those most suitable for measuring its expanding Homunculus Nebula. Multiple intensity tracings through the Homunculus reveal the fractional increase in the overall size of the nebula; this avoids registration uncertainty, mitigates brightness fluctuations, and is independent of previous methods. Combining a 13-yr baseline of Wide Field Planetary Camera 2 (WFPC2) images in the F631N filter, with a 4-yr baseline of Advanced Camera for Surveys/High Resolution Channel (ACS/HRC) images in the F550M filter, yields an ejection date (assuming linear motion) of 1847.1 ($\pm$0.8 yr). This result improves the precision, but is in excellent agreement with the previous study by Morse et al.\ (2001) that used a shorter time baseline and a different analysis method. This more precise date is inconsistent with ejection during a periastron passage of the eccentric binary. Ejection occured well into the main plateau of the Great Eruption, and not during the brief peaks in 1843 and 1838. The age uncertainty is dominated by a real spread in ages of various knots, and by some irregular brightness fluctuations. Several knots appear to have been ejected decades before or after the mean date, implying a complicated history of mass-loss episodes outside the main bright phase of the eruption. The extended history of mass ejection may have been largely erased by the passage of a shock through clumpy ejecta, as most material was swept into a thin shell with nearly uniform apparent age.

11 pages, 4 figs. Please see published MNRAS version for proper formating, readable figures, and online movie

References in corpus (13)

• Tycho Brahe's 1572 supernova as a standard type Ia explosion revealed from its light echo spectrum
• Scattered-Light Echoes from the Historical Galactic Supernovae Cassiopeia A and Tycho (SN 1572)
• A Blast Wave from the 1843 Eruption of Eta Carinae
• The Bubble-like Interior of the Core-Collapse Supernova Remnant Cassiopeia A
• Possible Implications of Mass Accretion in Eta Carinae
• Ancient eruptions of Eta Carinae: A tale written in proper motions
• The Structure of the Homunculus. II. Modeling the physical conditions in Eta Car's molecular shell
• The fossil wind structures of Eta Carinae: changes across on 5.54-year cycle
• Light Echoes from Eta Carinae's Great Eruption: Spectrophotometric Evolution and the Rapid Formation of Nitrogen-rich Molecules
• HH 666: Different kinematics from Hα and [Fe II] emission provide a missing link between jets and outflows
• VLTI-AMBER velocity-resolved aperture-synthesis imaging of Eta Carinae with a spectral resolution of 12000. Studies of the primary star wind and innermost wind-wind collision
• Kinematics of powerful jets from intermediate-mass protostars in the Carina nebula
• Dissecting a SN impostor's circumstellar medium: MUSEing about the SHAPE of eta Car's outer ejecta

Cited by in corpus (6)

• Simulating the formation of $\eta$ Carinae's surrounding nebula through unstable triple evolution and stellar merger-induced eruption
• Distinguishing Circumstellar from Stellar Photometric Variability in Eta Carinae
• A disrupted molecular torus around Eta Carinae as seen in 12CO with ALMA
• Luminous Blue Variables
• A six year image-subtraction light curve of SN 2010jl
• Long-term evolution in ionization of ejecta illuminated by Eta Carinae