Issue |
A&A
Volume 435, Number 1, May III 2005
|
|
---|---|---|
Page(s) | 167 - 175 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20042371 | |
Published online | 25 April 2005 |
A multiwavelength study of the remnant of nova GK Persei
1
Indian Institute of Astrophysics, II Block Koramangala, Bangalore 560 034, India e-mail: gca@iiap.res.in
2
National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Post Bag 3, Ganeshkhind, Pune 411 007, India e-mail: ngk@ncra.tifr.res.in
Received:
16
November
2004
Accepted:
20
January
2005
We present new observations of the nebular remnant of the old
nova GK Persei 1901 in the optical using the Himalayan Chandra Telescope (HCT)
and at low radio frequencies using the Giant Metrewave Radio Telescope (GMRT).
The dimensions of the shell in the optical emission lines of [NII], [OIII]
and [OII] are arcsec2,
arcsec2 and
arcsec2, respectively. The evolution of the nova remnant
indicates shock interaction with the ambient medium, especially in the
southwest quadrant. Application of a simple model for the shock
and its evolution to determine the time dependence of the radius of the shell
in the southwest quadrant indicates that the shell is now expanding into
an ambient medium that has a density of 0.12 cm-3, compared to the density
of the ambient medium of 0.8 cm-3 ahead of the shock in 1987.
There are indications of a recent interaction of the nova remnant with the
ambient medium in the northeast quadrant. There is a distinct flattening
of the shell, as well as an increase in the number and brightness of
the knots in the region. The brightest optical knots in this region are also
detected in the radio images.
The nova remnant of GK Per is detected at all the observed radio frequencies
and is of a similar extent to the optical remnant.
Putting together our radio observations with VLA archival data on GK Per from 1997, we
obtain three interesting results: 1. the spectrum
above 1.4 GHz follows a power law with an index -0.7 (
)
and below 1.4 GHz follows a power law with an index ∼-0.85. This could be due to
the presence of at least two populations of electrons dominating the global
emission at different frequencies;
2. we record an annual secular decrease of 2.1% in the flux density of the nova
remnant at 1.4 and 4.9 GHz between 1984 and 1997 which has left the spectral
index unchanged at -0.7. No such decrease is observed in the flux densities
below 1 GHz;
3. we record an increase in the flux density at 0.33 GHz compared to the
previous estimate in 1987. We conclude that the remnant of nova GK Per is
similar to supernova remnants and in particular to the young supernova remnant Cas A.
Key words: novae, cataclysmic variables / ISM: general
© ESO, 2005
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