Spatially resolved spectra of V1974 Cygni (Nova Cygni 1992) with the goddard high resolution spectrograph

Steven N. Shore, Sumner Starrfield, T. B. Ake, Peter H. Hauschildt

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

We report the observation of spatially resolved low-resolution GHRS spectra of the shell of the bright Galactic ONeMg nova Cygni 1992. The spectra were obtained in 1995 September, after the X-ray turnoff of the nova. We have determined the dynamical structure of the ejecta and show the evolution of the ionization within the ejecta. Abundance limits have been found to agree with the published analyses based on earlier WE data for key species in the ejecta, especially neon. The knot spectrum, obtained with the 0" 25 aperture, shows an enhanced Ne/He ratio compared with the 2" aperture observation. These data provide a detailed picture of physical conditions and abundances of the knots and larger scale ejecta that have not previously been available from UV spectra, including those taken before the COSTAR installation and WE data. The knots were created during the initial stages of the explosion, and the differential mixing that may have resulted can be studied using the spatially resolved spectra. The 1995 spectra were compared with archival Faint Object Spectrograph data from 1994 and previous GHRS spectra from 1992 and 1993. We also obtained high signal-to-noise ratio (S/N) observations of the UV continuum of the hot central star in order to study the physical conditions in the postthermonuclear runaway envelope. These show that the white dwarf had relaxed to a very low effective temperature, about 20,000 K, and a luminosity of about 30 L, within 2 years after the X-ray turnoff. We also used reprocessed archival WE spectra to determine the decay time for the ultraviolet continuum flux for this nova, which we find to be about 1.7 years. The current temperature and luminosity do not fall on the white dwarf cooling tracks for any reasonable stellar mass.

Original languageEnglish (US)
Pages (from-to)393-400
Number of pages8
JournalAstrophysical Journal
Volume490
Issue number1 PART I
DOIs
StatePublished - 1997

Fingerprint

spectrographs
high resolution
ejecta
apertures
luminosity
continuums
faint objects
neon
stellar mass
signal-to-noise ratio
installing
explosions
explosion
ionization
signal to noise ratios
x rays
envelopes
temperature
shell
cooling

Keywords

  • Novae, cataclysmic variables
  • Stars: individual (V1974 Cygni)
  • Ultraviolet: stars

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Spatially resolved spectra of V1974 Cygni (Nova Cygni 1992) with the goddard high resolution spectrograph. / Shore, Steven N.; Starrfield, Sumner; Ake, T. B.; Hauschildt, Peter H.

In: Astrophysical Journal, Vol. 490, No. 1 PART I, 1997, p. 393-400.

Research output: Contribution to journalArticle

Shore, Steven N. ; Starrfield, Sumner ; Ake, T. B. ; Hauschildt, Peter H. / Spatially resolved spectra of V1974 Cygni (Nova Cygni 1992) with the goddard high resolution spectrograph. In: Astrophysical Journal. 1997 ; Vol. 490, No. 1 PART I. pp. 393-400.
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N2 - We report the observation of spatially resolved low-resolution GHRS spectra of the shell of the bright Galactic ONeMg nova Cygni 1992. The spectra were obtained in 1995 September, after the X-ray turnoff of the nova. We have determined the dynamical structure of the ejecta and show the evolution of the ionization within the ejecta. Abundance limits have been found to agree with the published analyses based on earlier WE data for key species in the ejecta, especially neon. The knot spectrum, obtained with the 0" 25 aperture, shows an enhanced Ne/He ratio compared with the 2" aperture observation. These data provide a detailed picture of physical conditions and abundances of the knots and larger scale ejecta that have not previously been available from UV spectra, including those taken before the COSTAR installation and WE data. The knots were created during the initial stages of the explosion, and the differential mixing that may have resulted can be studied using the spatially resolved spectra. The 1995 spectra were compared with archival Faint Object Spectrograph data from 1994 and previous GHRS spectra from 1992 and 1993. We also obtained high signal-to-noise ratio (S/N) observations of the UV continuum of the hot central star in order to study the physical conditions in the postthermonuclear runaway envelope. These show that the white dwarf had relaxed to a very low effective temperature, about 20,000 K, and a luminosity of about 30 L⊙, within 2 years after the X-ray turnoff. We also used reprocessed archival WE spectra to determine the decay time for the ultraviolet continuum flux for this nova, which we find to be about 1.7 years. The current temperature and luminosity do not fall on the white dwarf cooling tracks for any reasonable stellar mass.

AB - We report the observation of spatially resolved low-resolution GHRS spectra of the shell of the bright Galactic ONeMg nova Cygni 1992. The spectra were obtained in 1995 September, after the X-ray turnoff of the nova. We have determined the dynamical structure of the ejecta and show the evolution of the ionization within the ejecta. Abundance limits have been found to agree with the published analyses based on earlier WE data for key species in the ejecta, especially neon. The knot spectrum, obtained with the 0" 25 aperture, shows an enhanced Ne/He ratio compared with the 2" aperture observation. These data provide a detailed picture of physical conditions and abundances of the knots and larger scale ejecta that have not previously been available from UV spectra, including those taken before the COSTAR installation and WE data. The knots were created during the initial stages of the explosion, and the differential mixing that may have resulted can be studied using the spatially resolved spectra. The 1995 spectra were compared with archival Faint Object Spectrograph data from 1994 and previous GHRS spectra from 1992 and 1993. We also obtained high signal-to-noise ratio (S/N) observations of the UV continuum of the hot central star in order to study the physical conditions in the postthermonuclear runaway envelope. These show that the white dwarf had relaxed to a very low effective temperature, about 20,000 K, and a luminosity of about 30 L⊙, within 2 years after the X-ray turnoff. We also used reprocessed archival WE spectra to determine the decay time for the ultraviolet continuum flux for this nova, which we find to be about 1.7 years. The current temperature and luminosity do not fall on the white dwarf cooling tracks for any reasonable stellar mass.

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KW - Ultraviolet: stars

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