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Williams, Peter; Quinsee, Susannah

doi:10.1108/ap.2005.27657baa.001

Cited by 2 publications

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“…The outer, narrower parts of the comet-like features often terminate in a bright knot, suggestive of a shock interaction of the outflowing ejecta with a stationary or slower moving medium. The observational case for large amounts of circum-binary matter surrounding, and interacting with the ejecta of novae is given in Williams & Mason (2010). The morphologies we see in the outer parts of some of the GK Per comet-like features are consistent with blobs of ejecta running into a pre-existing ambient medium.…”

Section: Hst Images Of Gk Permentioning

confidence: 72%

GK Per (Nova Persei 1901):HUBBLE SPACE TELESCOPEIMAGERY AND SPECTROSCOPY OF THE EJECTA, AND FIRST SPECTRUM OF THE JET-LIKE FEATURE

Shara

Zurek

Marco

et al. 2012

The Astronomical Journal

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We have imaged the ejecta of GK Persei (Nova Persei 1901 A.D.) with the Hubble Space Telescope (HST), whose 0.1 arcsec resolution reveals hundreds of cometary-like structures with long axes aligned towards GK Per. One or both ends of the structures often show a brightness enhancement relative to the structures' middle sections, but there is no simple regularity to their morphologies (in contrast with, for example, the Helix nebula). Some of structures' morphologies suggest the presence of slow-moving or stationary material with which the ejecta is colliding, while others suggest shaping from a wind emanating from GK Per itself. The most detailed expansion map of any classical nova's ejecta was created by comparing HST images taken in successive years. Wide Field and Planetary Camera 2 narrowband images and Space Telescope Imaging Spectrograph spectra demonstrate that the physical conditions in this nova's ejecta vary strongly on spatial scales much smaller than those of the ejecta. Directly measuring accurate densities and compositions, and hence masses of this and other nova shells, will demand data at least as resolved spatially as those presented here. The filling factor the ejecta is 1 % or less, and the nova ejecta mass must be less than 10 −4 M . A modest fraction of the emission nebulosities vary in brightness by up to a factor of two on timescales of one year. Finally, we present the deepest images yet obtained of a jet-like feature outside the main body of GK Per nebulosity, and the first spectrum of that feature. Dominated by strong, narrow emission lines of [NII], [OII], [OIII], and [SII], this feature is probably a shock due to ejected material running into stationary ISM, slowly moving ejecta from a previous nova episode, or circum-binary matter present before 1901. An upper limit to the mass of the jet is of order a few times 10 −6 M . If the jet mass is close to this limit then the jet might be an important, or even dominant mass -3sink from the binary system. The jet's faintness suggests that similar features could easily have been missed in other cataclysmic binaries.

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Section: Hst Images Of Gk Permentioning

confidence: 72%

GK Per (Nova Persei 1901):HUBBLE SPACE TELESCOPEIMAGERY AND SPECTROSCOPY OF THE EJECTA, AND FIRST SPECTRUM OF THE JET-LIKE FEATURE

Shara

Zurek

Marco

et al. 2012

The Astronomical Journal

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“…Other evidence for separate Fe II and He/N emission regions may come from transient 'thea' absorbing systems that were studied in the FEROS survey (Williams et al 2008). Thea absorption has so far been observed only in Fe II-type spectra and Williams & Mason (2010) argued that the absorbing gas is present in pre-outburst shells. However, high resolution observations of thea absorption in the recent T Pyxidis outburst by Ederoclite et al (2012) detected a thea system that was not present at the time of outburst but emerged only some weeks afterward when T Pyx had entered its Fe II spectral phase, casting doubt on the Williams & Mason hypothesis.…”

Section: Test Of the Hypothesismentioning

confidence: 99%

ORIGIN OF THE “He/N” AND “Fe II” SPECTRAL CLASSES OF NOVAE

Williams

2012

The Astronomical Journal

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Abstract. The spectra of postoutburst novae display either He+N or Fe II lines as the most prominent non-Balmer lines at maximum light. Spectral diagnostics indicate physical conditions for 'He/N' spectra that are consistent with their origin in the white dwarf (WD) ejecta, whereas 'Fe II' spectra point to their formation in a large circumbinary envelope of gas whose origin is the secondary star. A determining parameter for which of the two types of spectra predominates may be the binary mass ratio M sec /M WD . The increasing fraction of novae that are observed to be 'hybrid' objects, where both classes of spectra appear sequentially, is explained by changing parameters in the two emitting regions during the postoutburst decline. We argue that most novae may be hybrids that show both types of spectra during decline. The emission line intensity ratio O I λ8446/λ7773 is suggested as a good density diagnostic for the ejecta, and a finding list of emission lines identified in recent spectroscopic surveys of novae is presented as an aid to future line identification work.

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Cited by 2 publications

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GK Per (Nova Persei 1901):HUBBLE SPACE TELESCOPEIMAGERY AND SPECTROSCOPY OF THE EJECTA, AND FIRST SPECTRUM OF THE JET-LIKE FEATURE

GK Per (Nova Persei 1901):HUBBLE SPACE TELESCOPEIMAGERY AND SPECTROSCOPY OF THE EJECTA, AND FIRST SPECTRUM OF THE JET-LIKE FEATURE

ORIGIN OF THE “He/N” AND “Fe II” SPECTRAL CLASSES OF NOVAE

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