GK Per (Nova Persei 1901) nova remnant is the result of a remarkable nearby nova exploded in 1901
which reached the brightness of the star Vega at its maximum. It was the first object around
which, superluminal light echoes where observed. The actual ejecta of the
outburst became visible 15 years later in 1916. Ever since, the ejecta has been
monitored in several wavelengths in narrow- and broad-band filters.
This study, conducted by astronomers from Spain and Estonia, shows that the nova ejecta is a
thick knotty shell in which knots expand with a significant range of velocities,
mostly between 600 and 1000 km/s. Being relatively close to us (400 pc),
the apparent growth of the GK Per knotty remnant is about one
arcsec per year, which is easily resolvable with ground-based telescopes even
on a timescale of a few months. For these reasons, since 2004 the expansion of the
GK Per remnant has been monitored with the Wide Field Camera (WFC) on the Isaac Newton Telescope (INT).
To get the real expansion velocities of the individual knots of the remnant and thus
the three-dimensional view of the remnant, long-slit spectroscopy using INT+IDS and NOT+ALFOSC was also obtained.
This video shows the apparent expansion of the Nova Persei 1901
optical remnant from 1953 to 2011. The animation includes the
early photographic and CCD images, astrometrically matched to the
recent ones but in an arbitrary intensity scale and with a generally
poor resolution, as well as a selection of the best INT images in the
sequence of highly homogeneous data taken from 2004 onwards, in the
same linear intensity scale. Not only the overall expansion of the outflow is
clearly revealed, but also changes in brightness of some of the knots in
timescales of a few years are detected and can be studied in detail.
Credit: Liimets et al., 2012, ApJ, 761, 34 and AAS.
[ YouTube | Liimets' web site ].
In all directions, the optical knots are expanding quasi
ballistically and have suffered only a modest deceleration since their ejection a century ago.
Therefore, previous results from radio and X-ray works, which predicted a strong deceleration
of the ejecta in specific directions due to interaction with the circumstellar medium,
are not supported by the analysis of the new data.
T. Liimets, R.L.M. Corradi, M. Santander-García, E. Villaver, P. Rodríguez-Gil, K. Verro,
and I. Kolka, 2012, "A three-dimensional view of the remnant of Nova Persei 1901 (GK Per)", ApJ, 761, 34.