A three-dimensional view of the remnant of Nova Persei 1901 (GK Per)

The Astrophysical Journal 761.1 (2012): 34 reproduced by permission of the AASWe 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.The work of R.L.M.C. and M.S.G. has been supported by the Spanish Ministry of Science and Innovation (MICINN) under the grantAYA2007-66804. P.R.G. is supported by a Ramón y Cajal fellowship (RYC–2010–05762). E.V. acknowledges the support provided by the Spanish MICINN under grant AYA2010-20630 and to the Marie Curie FP7-People-RG268111. This work was partially supported by the Spanish MICINN under the CONSOLIDER–INGENIO 2010 Program, through the grants “Molecular Astrophysics: The Herschel andALMAEraASTROMOL” (CSD2009–00038) and “First Science with the GTC” (CSD2006–00070). T.L., K.V., and I.K. acknowledge the support of the Estonian Ministry for Education and Science