Other
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011phdt.........1r&link_type=abstract
PhD Thesis, Liverpool John Moores University, 2011
Other
2
Novae, Cataclysmic Variables, Line: Profiles, Binaries: Symbiotic, Circumstellar Matter, Stars: Individual: Rs Ophiuchi, Stars: Individual: V2491 Cygni, Stars: Individual: V2672 Ophiuchi, Stars: Individual: Kt Eridani
Scientific paper
Classical and recurrent nova outbursts occur on the surface of a white dwarf in a close binary system. It is widely established that the outburst is due to a thermonuclear runaway. Their study provides a real-time laboratory for the understanding of a wide range of astrophysical phenomena. These include for example, mass transfer in close binary systems, nuclear powered outbursts, dust formation, mass loss from red giants, and many others. Recurrent novae have also been suggested as the progenitors of Type Ia Supernovae.
This thesis concentrates on investigating the nebular remnants of novae by studying both resolved imaging (where available) and spectroscopic evolution and combining this with detailed modelling. Such studies have wider implications for example in our understanding of the shaping of proto-Planetary Nebulae.
Here, using a morpho-kinematical code, the true 3D geometry, from which information such as the remnant's inclination angle and expansion velocity can be derived, of the recurrent nova RS Ophiuchi and classical novae V2491 Cygni, V2672 Ophiuchi and KT Eridani are established and related to other characteristics of each system. Each of the classical novae have also been suggested as a recurrent nova candidate. Furthermore, several enhancements to the modelling code were implemented prompted by the work described in this thesis.
The RS Oph work entailed detailed modelling of Hubble Space Telescope resolved imaging combined with ground-based spectroscopic observations. Here it was shown that the bipolar morphology of RS Oph consisted of two distinct components with an outer dumbbell and an inner hour glass overdensity, which were required to reproduce both the observed images and spectra. This morphology was suggested to arise due to the interaction between the pre-existing anisotropic red-giant wind and the ejecta. The observed asymmetry in the ACS/HRC image was shown to be due to the finite width and offset from the [OIII] line's rest wavelength of the F502N filter. This in turn gave valuable information on the spatial orientation of the nebula. The inclination angle was derived to be 39+1-10 degrees, comparable with estimates of the inclination of the central binary. Furthermore, it was also suggested, when comparing two different epochs, that there was evidence for some deceleration of the inner hour glass while the outer dumbbell expanded linearly. This linear expansion is also confirmed with X-ray observations.
In the case of V2491 Cyg, V2672 Oph and KT Eri, no resolved imaging was available primarily due to their distances versus time since outburst. The modelling here concentrated on reproducing the Hα line profile at various outburst epochs to derive their true geometry.
V2491 Cyg, was explored using the first scientific results for the Liverpool Telescope prototype spectrograph. These were best-fit using a morphology with polar blobs and an equatorial ring with an inclination angle of 80+3-12 degrees and a maximum expansion velocity of the polar blobs of 3100+200-100 km s-1 and for the equatorial ring of 2700+200-100 km s-1. Multi-epoch fitting showed that the line profile at later times consisted of a combination of Hα and [NII] emission. Furthermore, the derived inclination implies that eclipses should be observed for which a search is now underway. In addition, the amplitude versus time of decline from maximum relationship, at the inclination derived, may imply a recurrent nova nature of V2491 Cyg.
V2672 Oph's derived nebular morphology was that of polar blobs and an equatorial ring with an underlying prolate structure which seemed to reduce in relative density with time compared to the other components. The inclination of the system was suggested to be 0±6 degrees and a maximum expansion velocity Vexp = 4800+900-800 km s-1. The morphology found here is incompatible with that expected for a fast nova which may again lend support for a recurrent nova nature of V2672 Oph.
In KT Eri, optical spectroscopy, using a combination of second generation spectrograph on the Liverpool Telescope and those of more established observatories, and X-ray observations were compared to determine that the emergence of the He II 4686Å line is related to the emergence of the super-soft source (SSS) phase in the X-ray. This could be a useful tool as a trigger for future X-ray observations. The SSS phase is an important phase for observations because it samples the continued extensive nuclear burning on the surface of the white dwarf following outburst. Morpho-kinematical modelling suggested that the morphology of the remnant was that of a dumbbell with a ratio between the major to minor axis of 4:1 with an inclination of 58+6-7 degrees and the maximum expansion velocity Vexp = 2800±200 km s-1.
Future enhancements to the modelling code are suggested. Furthermore, the results given here present sufficient scientific motivation to justify for example a renewed program of Hubble Space Telescope observations of nova remnants.
No associations
LandOfFree
Investigation of the Nebular Remnants of Novae does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Investigation of the Nebular Remnants of Novae, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Investigation of the Nebular Remnants of Novae will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1609435