Publications of the MPIfR
Optical & Infrared
Interferometry Group
Ueta, T., Murakawa, K., Meixner, M.
Proper-Motion Measurements of the Cygnus Egg
Nebula
The Astrophysical Journal, Volume 641, Issue 2, pp.
1113-1121
Abstract
We present the results of proper-motion measurements of the dust shell
structure in the Egg Nebula (AFGL 2688, CRL 2688, V1610 Cyg), based on
the archived two-epoch data at 2 μm taken with the Hubble Space
Telescope. We measured the amount of motion of local structures in the
nebula by determining their relative shifts over an interval of 5.5 yr.
The dynamical age of the nebula is found to be roughly 350 yr based on
the overall Hubble-law-esque motion of the nebula. By adopting the
deprojected velocity of 45 km s-1 at the tips of the bipolar
lobes, our proper-motion measurements indicate that the distance to the
Egg Nebula is about 420 pc and that the lobes are inclined at 7.7d with
respect to the plane of the sky. The refined distance estimate yields a
luminosity of the central star of 3.3×103
Lsolar, a total shell mass of 1.2 Msolar, and a
mass-loss rate (the upper limit) of 3.6×10-3
Msolar yr-1. Assuming a 0.6 Msolar
central post-AGB stellar mass, the initial mass of the Egg is 1.8
Msolar. Upon analysis, we also discovered that (1) the
central star of the Egg Nebula has a proper motion of its own at a rate
of 17 mas yr-1, (2) the tips of the lobes increased their
velocity due to shock acceleration, and (3) the apparent bipolar lobes
consist of multiple outflows at distinct inclination angles projected
onto each other.
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