5,801 research outputs found
The Evolution of Nova Remnants
In this review I concentrate on describing the physical characteristics and
evolution of the nebular remnants of classical novae. I also refer as
appropriate to the relationship between the central binary and the ejected
nebula, particularly in terms of remnant shaping. Evidence for remnant
structure in the spectra of unresolved novae is reviewed before moving on to
discuss resolved remnants in the radio and optical domains. As cited in the
published literature, a total of 5 remnants have now been resolved in the radio
and 44 in the optical. This represents a significant increase since the time of
the last conference. We have also made great strides in understanding the
relationship of remnant shape to the evolution of the outburst and the
properties of the central binary. The results of various models are presented.
Finally, I briefly describe new results relating to the idiosyncratic remnant
of GK Per (1901) which help to explain the apparently unique nature of the
evolving ejecta before concluding with a discussion of outstanding problems and
prospects for future work.Comment: 12 pages, 8 figures. Invited review in the Proceedings of the
Conference "Classical Nova Explosions" (Sitges, May 2002), M. Hernanz and J.
Jose eds., published by the American Institute of Physic
Classical and Recurrent Nova Outbursts
Over the last 40 years, multi-frequency observations, coupled with advances
in theoretical modelling, have led to a much fuller understanding of the nova
phenomenon. Here I give a brief review of the current state of knowledge of
Classical and Recurrent Novae including their central systems; the causes and
consequences of their outbursts; sub-types, and possible relationships to Type
Ia Supernovae. Particular attention is paid to the Recurrent Nova RS Ophiuchi
as it shows a wealth of phenomena associated with its 2006 outburst. Finally,
some open questions and avenues for future work are summarised.Comment: 10 pages, 2 figures. Review paper submitted to the proceedings of the
11th Asian-Pacific Regional IAU Meeting 2011, NARIT Conference Series, Vol.
1, 2012. S. Komonjinda, Y. Kovalev, and D. Ruffolo, ed
Statistics of Quasars Multiply Imaged by Galaxy Clusters
We compute the expected number of quasars multiply imaged by cluster size
dark halos for current wide field quasar surveys by carrying out a large
ensemble of ray tracing simulations through clusters from a cosmological N-body
simulation of the LCDM cosmology. Our calculation predicts ~ 4 quasar lenses
with splittings theta > 10" in the SDSS spectroscopic quasar sample, consistent
with the recent discovery of the wide separation lens SDSSJ1004+4112 which has
theta=14.6". The SDSS faint photometric quasar survey will contain ~12 multiply
imaged quasars with splittings theta > 10". Of these, ~ 2 will be lenses with
separations theta > 30", and ~ 2 will be at high redshift (z ~ 4).Comment: 6 pages, 3 Figures, submitted to Ap
Flickering variability of T Coronae Borealis
We present electro-photometric UBV and high-speed U-band flickering
observations of the recurrent nova T CrB during a period when its U brightness
varies by more than 2 mag. The V band is dominated by the ellipsoidal
variability of the red giant, however, the variability of the hot component
also causes 0.15 mag variations in V. We define a set of parameters which
characterise the flickering. The Fourier spectra of all 27 nights are similar
to each other. The power spectral density of the variations has a power law
component (f^{-1.46} on average). We do not detect a dependence of the Fourier
spectra and autocorrelation function on the brightness of the object. Having
subtracted the contribution of the red giant, we show that the flickering
amplitude correlates with the average flux of the accreting component. A
comparison with CH Cyg and MWC 560 indicates that the flickering of T CrB is
more stable (at least during the time of our observations), than that in the
jet-ejecting symbiotic stars. The data are available in electronic form from
the authors.Comment: 8 pages, 6 figures, 2 tables, accepted for publication in MNRA
Liverpool Telescope Optical Photometry Following the 2006 Outburst of RS Ophiuchi
We present a preliminary report on the broadband optical photometry of the
2006 outburst of the recurrent nova RS Ophiuchi. These data were obtained using
the robotic 2m Liverpool Telescope and cover the outburst from day 27 through
day 548.Comment: 3 pages, 2 figures, to appear in ASP conference proceedings Volume
401 "RS Ophiuchi (2006) and the recurrent nova phenomenon
On the Evolution of the Late-time {\it Hubble Space Telescope} Imaging of the Outburst of the Recurrent Nova RS Ophiuchi (2006)
We modelled the late-time {\it Hubble Space Telescope} imaging of RS Ophiuchi
with models from Ribeiro et al. (2009), which at the time due to the unknown
availability of simultaneous ground-based spectroscopy left some open questions
as to the evolution of the expanding nebular from the early to the late time
observations. Initial emission line identifications suggest that no forbidden
lines are present in the spectra and that the emission lines arising in the
region of the WFPC2 F502N images are due to N{\sc ii} and He{\sc i} + Fe{\sc
ii}. The best model fit to the spectrum is one where the outer faster moving
material expands linearly with time while the inner over-density material
either suffered some deceleration or did not change in physical size. The
origin of this inner over-density requires further exploration.Comment: 6 pages, 3 figures, to appear in Stella Novae: Past and Future
Decades, P. A. Woudt & V. A. R. M. Ribeiro (eds), ASPCS 49
The Evolution of Nova Ejecta
In this paper I review the basic parameters of Classical Novae and then move
on to describe the evolution of their ejected envelopes. The early shaping of
the remnant, thought to be a consequence of a common envelope phase, and with
analogies to what may occur in PNe with binary star nuclei, is then described.
Finally, the curious case of Nova GK Persei (1901) and its potential to aid our
understanding of both nova and long-term PN evolution is discussed.Comment: To be submitted to the Proceedings of Asymmetrical Planetary Nebulae
III, eds. M. Meixner, J. H. Kastner, and N. Soker, ASP Conf. Series; 7 pages,
4 figures; Draft: will be revised according to comments by readers and other
papers submitted to the Proceeding
High Spatial Resolution Optical and Radio Imagery of the Circumbinary Environment
In this review, I concentrate on describing observations of spatially
resolved emission in symbiotic stars at sub-arcsecond scales. In some of the
closer objects, the highest resolutions discussed here correspond to linear
dimensions similar to the supposed binary separation. A total of 17 stars well
accepted as symbiotics are now observed to show sub-arcsecond structure, almost
twice the number at the time of the last review in 1987. Furthermore, we now
have access to HST imagery to add to radio interferometry. From such
observations we can derive fundamental parameters of the central systems,
investigate the variation of physical parameters across the resolved nebulae
and probe the physical mechanisms of mass loss and interactions between ejecta
and the circumstellar medium.
Suggestions for future work are made and the potential of new facilities in
both the radio and optical domains is described. This review complements that
by Corradi (this volume) which mainly considers the larger scale emission from
the ionized nebulae of these objects.Comment: 17 pages, 9 figures, to appear in "Symbiotic Stars Probing Stellar
Evolution", eds. R. L. M. Corradi, J. Mikolajewska, and T. J. Mahoney, ASP
Conference Serie
Spectroscopic and Photometric Development of T Pyxidis (2011) from 0.8 to 250 Days After Discovery
We investigated the optical light curve of T Pyx during its 2011 outburst
through compiling a database of SMEI and AAVSO observations. The SMEI light
curve, providing unprecedented detail with high cadence data during t=1.5-49
days post-discovery, was divided into four phases based on the idealised nova
optical light curve; the initial rise, the pre-maximum halt (or the 'plateau'),
the final rise, and the early decline. Variation in the SMEI light curve
reveals a strongly detected period of 1.44\pm0.04 days before the visual
maximum. The spectra from the LT and SMARTS telescopes were investigated during
t=0.8-80.7 and 155.1-249.9 days. The nova was observed very early in its rise
and a distinct high velocity ejection phase was evident. A marked drop and then
gradual increase in derived ejection velocities were present. Here we propose
two different stages of mass loss, a short-lived phase occurring immediately
after outburst followed by a more steadily evolving and higher mass loss phase.
The overall spectral development follows that typical of a Classical Nova and
comparison to the photometric behaviour reveals consistencies with the simple
evolving pseudo-photosphere model of the nova outburst. The optical spectra are
also compared to X-ray and radio light curves. Weak [Fe X] 6375A emission was
marginally detected before the rise in X-ray emission. The middle of the
plateau in the X-ray light curve is coincident with the appearance of high
ionization species detected in optical spectra and the peak of the high
frequency radio flux.Comment: 6 pages, 4 figure
On the M31 Nova Progenitor Population
We present a survey of M31 novae in quiescence. This is the first catalogue
of extragalactic systems in quiescence and contains 37 spectroscopically
confirmed novae from 2006 to 2013. We used Liverpool Telescope and Faulkes
Telescope North images taken during outburst to identify accurate positions for
each system. These positions were then transformed to archival Hubble Space
Telescope (HST) images and we performed photometry on any resolvable source
that was consistent with the transformed positions. As red giants in M31 will
be resolvable in the HST images, we can detect systems with red giant
secondaries. There are only a few confirmed examples of such systems in our
Galaxy (e.g. RS Oph and T CrB). However, we find a much higher portion of the
nova population in M31 may contain red giant secondaries. For some novae,
coincident HST images had been taken when the nova was still fading, allowing
us to produce light curves that go fainter than is possible to achieve for most
extragalactic systems. Finally, we compare the M31 and Galactic quiescent nova
populations.Comment: 6 pages, 3 figures, to appear in Stella Novae: Future and Past
Decades, P. A. Woudt & V. A. R. M. Ribeiro (eds), ASPC
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