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Post Info TOPIC: Nova RS Ophiuchi
Blobrana


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RS Ophiuchi
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Title: High-resolution optical spectroscopy of RS Ophiuchi during 2008 -- 2009
Author: A. Somero, P. Hakala, G.A. Wynn

RS Ophiuchi is a symbiotic variable and a recurrent nova. We have monitored it with the Nordic Optical Telescope and obtained 30 high resolution (R=46 000) optical spectra over one orbital cycle during quiescence. To our knowledge this is the best-sampled high resolution spectroscopic dataset of RS Oph over one orbital period. We do not detect any direct signatures of an accretion disc such as double peaked emission lines, but many line profiles are complex consisting of superimposed emission and absorption components. We measure the spin of the red giant and conclude that it is tidally locked to the binary orbit. We observe Na I absorption features, probably arising from the circumbinary medium, that has been shaped by previous recurrent nova outbursts. We do not detect any intrinsic polarisation in the optical wavelengths.

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Blobrana


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RE: Nova RS Ophiuchi
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On February 12, 2006 an outburst of RS Ophiuchi occurred

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RS Ophiuchi.kmz
Google Sky File



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Blobrana


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Title: Disc instability in RS Ophiuchi: a path to Type Ia supernovae?
Authors: R.D.Alexander, G.A.Wynn, A.R.King, J.E.Pringle

We study the stability of disc accretion in the recurrent nova RS Ophiuchi. We construct a one-dimensional time-dependent model of the binary-disc system, which includes viscous heating and radiative cooling and a self-consistent treatment of the binary potential. We find that the extended accretion disc in this system is always unstable to the thermal-viscous instability, and undergoes repeated disc outbursts on ~10-20yr time-scales. This is similar to the recurrence time-scale of observed outbursts in the RS Oph system, but we show that the disc's accretion luminosity during outburst is insufficient to explain the observed outbursts. We explore a range of models, and find that in most cases the accretion rate during outbursts reaches or exceeds the critical accretion rate for stable nuclear burning on the white dwarf surface. Consequently we suggest that a surface nuclear burning triggered by disc instability may be responsible for the observed outbursts. This allows the white dwarf mass to grow over time, and we suggest that disc instability in RS Oph and similar systems may represent a path to Type Ia supernovae.

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Blobrana


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Title: Connecting RS OPh to [some] Type Ia Supernovae
Authors: F. Patat, N.N. Chugai, Ph. Podsiadlowski, E. Mason, C. Melo, L. Pasquini

    Aims: Recurrent nova systems like RS Oph have been proposed as a possible channel to Type Ia Supernova explosions, based on the high mass of the accreting white dwarf. Additional support to this hypothesis has been recently provided by the detection of circumstellar material around SN2006X and SN2007le, showing a structure compatible with that expected for recurrent nova outbursts. In this paper we investigate the circumstellar environment of RS Oph and its structure, with the aim of establishing a firmer and independent link between this class of objects and Type Ia SN progenitors.
    Methods: We study the time evolution of CaII, NaI and KI absorption features in RS Oph, before, during, and after the last outburst, using multi-epoch, high-resolution spectroscopy, and applying the same method adopted for SN2006X and SN2007le.
    Results: A number of components, blue-shifted with respect to the systemic velocity of RS Oph, are detected. In particular, one feature strongly weakens in the first two weeks after the outburst, simultaneously with the disappearance of very narrow P-Cyg profiles overimposed on the much wider nova emission lines of H, He, FeII and other elements.
    Conclusions: We interpret these facts as the signature of density enhancements in the circumstellar material, suggesting that the recurrent eruptions might indeed create complex structures within the material lost by the donor star. This establishes a strong link between RS Oph and the progenitor system of the Type Ia SN2006X, for which similar features have been detected.

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Blobrana


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Posts: 131433
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Recurrent Novae
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Title: Recurrent Novae: Progenitors of SN Ia?
Authors: Rolf Walder (1), Doris Folini (1), Jean M. Favre (2), Steven N. Shore (3) ((1) Ecole Normale Superieure, Lyon, CRAL, France, (2) Swiss National Supercomputing Centre, CSCS, Switzerland, (3) Dipartimento di Fisica "Enrico Fermi", Universita di Pisa and INFN-Sezione di Pisa, Italy)

We present 3D hydrodynamical simulations of the separated binary RS Ophiuchi (RS Oph), a recurrent nova and potential progenitor of a SN Ia. RS Oph is composed of a red giant (RG) and a white dwarf (WD) whose mass is close to the Chandrasekhar limit. In an isothermal scenario, the WD accretes about 10% of a 20 km/s RG wind by a non-Keplerian accretion disk with strong spiral shocks, and about 2% of a 60 km/s RG wind by what we term a 'turbulent accretion ball'. A significantly larger impact have the thermodynamics. In an adiabatic scenario only about 0.7% of the 20 km/s RG wind is accreted. The rate of change of the system separation due to mass and angular momentum loss out of the system is negative in all three cases studied, but is ten times smaller for a fast RG wind (60 km/s) than for a slow RG wind (20 km/s). The results demonstrate that existing nova models and observed recurrence times fit well together with 3D wind accretion and that RS Oph is one of the most promising systems to become an SN Ia.

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Blobrana


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Posts: 131433
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Recurrent Nova RS Ophiuchi
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Title: The Expanding Nebular Remnant of the Recurrent Nova RS Ophiuchi (2006): II. Modelling of Combined Hubble Space Telescope Imaging and Ground-based Spectroscopy
Authors: V. A. R. M. Ribeiro (1), M. F. Bode (1), M. J. Darnley (1), D. J. Harman (1), A. M. Newsam (1), T. J. O'Brien (2), J. Bohigas (3), J. M. Echevarría (3), H. E. Bond (4), V. H. Chavushyan (5), R. Costero (3), R. Coziol (6), A. Evans (7), S. P. S. Eyres (8), J. León-Tavares (5 and 9), M. G. Richer (3), G. Tovmassian (3), S. Starrfield (10), S. V. Zharikov (3) ((1) Liverpool John Moores University, UK, (2) University of Manchester, UK, (3) Universidad Nacional Autónoma de México, México, (4) Space Telescope Science Institute, USA, (5) Instituto Nacional de Astrofísica Óptica y Electrónica, México, (6) Universidad de Guanjuato, México, (7) Keele University, UK, (8) University of Central Lancashire, UK, (9) Max-Planck-Institut für Radioastronomie, Germany, (10) Arizona State University, USA)

We report Hubble Space Telescope imaging, obtained 155 and 449 days after the 2006 outburst of the recurrent nova RS Ophiuchi, together with ground-based spectroscopic observations, obtained from the Observatorio Astronomico Nacional en San Pedro Martir, Baja California, Mexico and at the Observatorio Astrofisico Guillermo Haro, at Cananea, Sonora, Mexico. The observations at the first epoch were used as inputs to model the geometry and kinematic structure of the evolving RS Oph nebular remnant. We find that the modelled remnant comprises two distinct co-aligned bipolar components; a low-velocity, high-density innermost (hour glass) region and a more extended, high-velocity (dumbbell) structure. This overall structure is in agreement with that deduced from radio observations and optical interferometry at earlier epochs. We find that the asymmetry observed in the west lobe is an instrumental effect caused by the profile of the HST filter and hence demonstrate that this lobe is approaching the observer. We then conclude that the system has an inclination to the line of sight of 39^{+1}_{-10} degrees. This is in agreement with the inclination of the binary orbit and lends support to the proposal that this morphology is due to the interaction of the outburst ejecta with either an accretion disk around the central white dwarf and/or a pre-existing red giant wind that is significantly denser in the equatorial regions of the binary than at the poles. The second epoch HST observation was also modelled. However, as no spectra were taken at this epoch, it is more difficult to constrain any model. Nevertheless, we demonstrate that between the two HST epochs the outer dumbbell structure seems to have expanded linearly.

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Blobrana


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Posts: 131433
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RE: Nova RS Ophiuchi
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Appelées novæ, les explosions d'étoiles mettent en oeuvre des réactions nucléaires entre les atomes de l'étoile. Pour mieux comprendre ces phénomènes violents, les astrophysiciens étudient le rayonnement émis par certains types d'atomes, notamment le fluor-18 issu des réactions. Or, des chercheurs du Ganil (CEA-CNRS), en collaboration avec des équipes anglaises, belges, roumaines et françaises, viennent de déterminer que le fluor-18 serait moins abondant que prévu. Cette découverte réduit donc la chance d'observer le rayonnement émis par cet atome. Elle implique de nouvelles contraintes pour l'observation et la compréhension des novæ. Ces travaux viennent d'être publiés dans la revue Physical Review Letters.

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Blobrana


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Posts: 131433
Date:
RS Ophiuchi
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Title: Hubble Space Telescope Imaging of the Expanding Nebular Remnant of the 2006 Outburst of RS Ophiuchi
Authors: D. J. Harman (1), M. F. Bode (1), M. J. Darnley (1), T. J. O'Brien (2), H. E. Bond (3), S. Starrfield (4), A. Evans (5), S. P. S. Eyres (6), V. A. R. M. Ribeiro (1), J. M. Echevarria (7) ((1) Astrophysics Research Institute, Liverpool John Moores University, UK, (2) Jodrell Bank Observatory, University of Manchester, UK, (3) Space Telescope Science Institute, Baltimore, MD, USA, (4) Arizona State University, Tempe, AZ, USA, (5) Astronomy Group, Keele University, UK, (6) Centre for Astrophysics, University of Central Lancashire, UK, (7) Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Mexico)
(Version v2)

We report Hubble Space Telescope imaging obtained 155 days and 449 days after the 2006 outburst of RS Ophiuchi. Both epochs show evidence of extended emission, consistent with that seen in earlier radio observations, and a maximum expansion rate of 3200 ±300 km s^{-1} (in the plane of the sky). The extended structure is consistent with the remnant having a bipolar morphology with an inclination similar to that determined for the binary.

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Blobrana


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Posts: 131433
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RE: Nova RS Ophiuchi
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Using the NASA / ESA Hubble Space Telescope (HST), an international team of astronomers have taken the first optical images of a dramatic stellar outburst and discovered a peanut-shaped bubble expanding rapidly into space. Team member Valerio Ribeiro, a graduate student from Liverpool John Moores University will present their results on Wednesday 22nd April at the European Week of Astronomy and Space Science conference at the University of Hertfordshire.

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Blobrana


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Posts: 131433
Date:
RS Ophiuchi
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A thermonuclear explosion on a dead star has resulted in an expanding space bubble shaped like a peanut.
The unusual sight arose from an unstable pairing of two aged stars: a white dwarf and a red giant in the constellation of Ophiuchus, known collectively as RS Oph. Astronomers imaged the double-lobed peanut structure's material expanding outwards at between 1,000 and 3,000 kilometres per second.

"There are some astronomers who believe systems like this will ultimately explode as supernovae" - Valerio Ribeiro, an astrophysics researcher at Liverpool John Moores University in the UK.

Source 

Using the NASA / ESA Hubble Space Telescope (HST), an international team of astronomers have taken the first optical images of a dramatic stellar outburst and discovered a peanut-shaped bubble expanding rapidly into space. Team member Valerio Ribeiro, a graduate student from Liverpool John Moores University will present their results on Wednesday 22nd April at the European Week of Astronomy and Space Science conference at the University of Hertfordshire.

Source

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