A THREE-DIMENSIONAL VIEW OF THE REMNANT OF NOVA PERSEI 1901 (GK Per)

Abstract

We present a kinematical study of the optical ejecta of GK Per. It is based on proper-motion measurements of 282 knots from ∼20 images spanning 25 years. Doppler shifts are also computed for 217 knots. The combination of proper motions and radial velocities allows a unique three-dimensional view of the ejecta to be obtained. The main results are as follows: (1) the outflow is a thick shell in which knots expand with a significant range of velocities, mostly between 600 and 1000 km s −1 , (2) kinematical ages indicate that knots have suffered only a modest deceleration since their ejection a century ago, (3) no evidence for anisotropy in the expansion rate is found, (4) velocity vectors are generally aligned along the radial direction, but a symmetric pattern of non-radial velocities is also observed at specific directions, and (5) the total Hα+[N ii] flux has been linearly decreasing at a rate of 2.6% per year in the past decade. The eastern nebular side is fading at a slower rate than the western side. Some of the knots were displayed a rapid change of brightness during the 2004-2011 period. Over a longer timescale, a progressive circularization and homogenization of the nebula are taking place; (6) a kinematic distance of 400 ± 30 pc is determined. These results raise some problems with the previous interpretations of the evolution of GK Per. In particular, the idea of a strong interaction of the outflow with the surrounding medium in the southwest quadrant is not supported by our data.

Radio Frequency Models of Novae in Eruption. I. The Free-Free Process in Bipolar Morphologies

“…Pseudo-three-dimensional models based on cloudy are also being developed (rainy3d; Moraes & Diaz 2009 which can also account for clumpyness. We also note that a shell thickness of 0.25 is higher than that derived from photoionization modeling (e.g., Vanlandingham et al 2005;Munari et al 2008Munari et al , 2011b)-although photoionization modeling should also be constrained with multifrequency and multi-epoch observations (e.g., Schwarz et al 2001;Schwarz 2014)-and indeed also from recent geometrical studies of the resolved ejecta of GK Per (Liimets et al 2012, although this object may be somewhat of a special case).…”

“…A number of effects that were not consider but warrant some discussion include non-uniformity of the ejecta, both in terms of the filling factor and clumpyness as well as temperature variations in the ejecta. The ejecta, particularly at optical wavelengths, have been shown to be very clumpy (e.g., HR Del, GK Per, RR Pic, T Pyx, AT Cnc; Gill & O'Brien 1998;Harman & O'Brien 2003;Liimets et al 2012;Shara et al 1997Shara et al , 2012aShara et al , 2012bSlavin et al 1995). Williams (1994) had already suggested that the ejecta shell is not homogeneous, as measured from the optical line ratios of [O i] and that neutral gas could exist in clumps.…”

Modelling the structure and kinematics of the Firework nebula: The nature of the GK Persei nova shell and its jet-like feature

“…It had been previously believed that the expanding nova remnant was decelerating at a faster rate, based on rigorous analysis of proper motions and radial velocities of individual knots (Liimets et al 2012) (hereafter L12) came to the conclusion that the system is decelerating at a rate of at least 3.8 times slower than that derived by Duerbeck (1987). An eventual circularisation of the shell was proposed in L12.…”

Angular Expansion of Nova Shells

“…′′ 3-0. ′′ 5 yr −1 , which has been kept unchanged since their ejection a century ago (Shara et al 2012b;Liimets et al 2012). This is somehow surprising, because detailed analyses of individual knots reveal the notable interaction with each other and with the ISM (Harvey et al 2016).…”