V723 Cas (Nova Cassiopeiae 1995): MERLIN observations from 1996 to 2001

Heywood, Ian; O’Brien, T. J.; Eyres, S. P. S.; Bode, M. F.; Davis, R. J.

doi:10.1111/j.1365-2966.2005.09328.x

Cited by 23 publications

(23 citation statements)

References 14 publications

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“…(1979) and Heywood et al (2005). To demonstrate that the models developed in this paper are equivalent to those previously published in the first row in Table 2, we show the fit of one such model to a spherical model from this paper.…”

Section: Spherical Modelsmentioning

confidence: 81%

Radio Frequency Models of Novae in Eruption. I. The Free-Free Process in Bipolar Morphologies

Ribeiro

Chomiuk

Munari

et al. 2014

ApJ

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Observations of novae at radio frequencies provide us with a measure of the total ejected mass, density profile, and kinetic energy of a nova eruption. The radio emission is typically well characterized by the free-free emission process. Most models to date have assumed spherical symmetry for the eruption, although for as long as there have been radio observations of these systems, it has been known that spherical eruptions are too simplistic a geometry. In this paper, we build bipolar models of the nova eruption, assuming the free-free process, and show the effects of varying different parameters on the radio light curves. The parameters considered include the ratio of the minorto major-axis, the inclination angle, and shell thickness. We also show the uncertainty introduced when fitting spherical-model synthetic light curves to bipolar-model synthetic light curves. We find that the optically thick phase rises with the same power law (S ν ∝ t 2 ) for both the spherical and bipolar models. In the bipolar case, there is a "plateau" phase-depending on the thickness of the shell as well as the ratio of the minor-to major-axis-before the final decline, which follows the same power law (S ν ∝ t −3 ) as in the spherical case. Finally, fitting spherical models to the bipolar-model synthetic light curves requires, in the worst-case scenario, doubling the ejected mass, more than halving the electron temperature, and reducing the shell thickness by nearly a factor of 10. This implies that in some systems we have been over-predicting the ejected masses and under-predicting the electron temperature of the ejecta.

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Section: Spherical Modelsmentioning

confidence: 81%

Radio Frequency Models of Novae in Eruption. I. The Free-Free Process in Bipolar Morphologies

Ribeiro

Chomiuk

Munari

et al. 2014

ApJ

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“…This model has worked very well for a number of novae, including some that have been imaged with MERLIN and the VLA (e.g., V1500 Cyg, QU Vul, and V723 Cas; Hjellming et al 1979;Taylor et al 1988;Heywood et al 2005). Note that the overall shape of light curves determined by the Hubble-flow model is fixed by a small set of parameters: the distance d, ejected mass M ej , ejecta temperature T ej , outer ejecta velocity v ej , and ratio of inner to outer velocity (which is not relevant until late in the light curve evolution).…”

Section: Discussionmentioning

confidence: 99%

Expanded Very Large Array Nova Project Observations of the Classical Nova V1723 Aquilae

Krauss

Chomiuk

Rupen

et al. 2011

ApJ

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We present radio light curves and spectra of the classical nova V1723 Aql obtained with the Expanded Very Large Array (EVLA). This is the first paper to showcase results from the EVLA Nova Project, which comprises a team of observers and theorists utilizing the greatly enhanced sensitivity and frequency coverage of EVLA radio observations, along with observations at other wavelengths, to reach a deeper understanding of the energetics, morphology, and temporal characteristics of nova explosions. Our observations of V1723 Aql span 1-37 GHz in frequency, and we report on data from 14 to 175 days following the time of the nova explosion. The broad frequency coverage and frequent monitoring show that the radio behavior of V1723 Aql does not follow the classic Hubble-flow model of homologous spherically expanding thermal ejecta. The spectra are always at least partially optically thin, and the flux rises on faster timescales than can be reproduced with linear expansion. Therefore, any description of the underlying physical processes must go beyond this simple picture. The unusual spectral properties and light curve evolution might be explained by multiple emitting regions or shocked material. Indeed, X-ray observations from Swift reveal that shocks are likely present.

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“…A 1/r 2 density profile, as we inferred from α trans , corresponds to the mass being distributed uniformly over the velocities. Such a model has been applied to many historical novae, including V1974 Cyg (Hjellming 1996), V1500 Cyg (Seaquist et al 1980), QU Vul (Taylor et al 1988), and V723 Cas (Heywood et al 2005). Given the brightness temperature after day 200 of near 10 4 K, and the evolution of the radio spectrum from initially rising with frequency (as expected for an optically thick shell) to falling slightly with frequency (as expected for an optically thin shell) via the appearance of two distinct spectral breaks, we conclude that it is reasonable to use a Hubble-flow model to parametrize the ejecta that produced the late-time radio emission from V1723 Aql.…”

Section: The Hubble Flow Modelmentioning

confidence: 99%

Non-thermal radio emission from colliding flows in classical nova V1723 Aql

Weston

Sokoloski

Metzger

et al. 2016

Mon. Not. R. Astron. Soc.

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The importance of shocks in nova explosions has been highlighted by Fermi's discovery of γ-ray producing novae. Over three years of multi-band VLA radio observations of the 2010 nova V1723 Aql show that shocks between fast and slow flows within the ejecta led to the acceleration of particles and the production of synchrotron radiation. Soon after the start of the eruption, shocks in the ejecta produced an unexpected radio flare, resulting in a multi-peaked radio light curve. The emission eventually became consistent with an expanding thermal remnant with mass 2 × 10 −4 M ⊙ and temperature 10 4 K. However, during the first two months, the ∼ >10 6 K brightness temperature at low frequencies was too high to be due to thermal emission from the small amount of X-ray producing shock-heated gas. Radio imaging showed structures with velocities of 400 km s −1 (d/6 kpc) in the plane of the sky, perpendicular to a more elongated 1500 km s −1 (d/6 kpc) flow. The morpho-kinematic structure of the ejecta from V1723 Aql appears similar to nova V959 Mon, where collisions between a slow torus and a faster flow collimated the fast flow and gave rise to γ-ray producing shocks. Optical spectroscopy and X-ray observations of V1723 Aql during the radio flare are consistent with this picture. Our observations support the idea that shocks in novae occur when a fast flow collides with a slow collimating torus. Such shocks could be responsible for hard X-ray emission, γ-ray production, and double-peaked radio light curves from some classical novae.

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V723 Cas (Nova Cassiopeiae 1995): MERLIN observations from 1996 to 2001

Cited by 23 publications

References 14 publications

Radio Frequency Models of Novae in Eruption. I. The Free-Free Process in Bipolar Morphologies

Radio Frequency Models of Novae in Eruption. I. The Free-Free Process in Bipolar Morphologies

Expanded Very Large Array Nova Project Observations of the Classical Nova V1723 Aquilae

Non-thermal radio emission from colliding flows in classical nova V1723 Aql

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