A Chandra low energy transmission grating spectrometer observation of V4743 Sagittarii

A supersoft X-ray source and a violently variable light curve

J. U. Ness, Sumner Starrfield, V. Burwitz, R. Wichmann, P. Hauschildt, J. J. Drake, R. M. Wagner, H. E. Bond, J. Krautter, M. Orio, M. Hernanz, R. D. Gehrz, C. E. Woodward, Y. Butt, K. Mukai, S. Balman, J. W. Truran

Research output: Contribution to journalArticle

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Abstract

V4743 Sagittarii (Nova Sgr 2002 No. 3) was discovered on 2002 September 20. We obtained a 5 ks ACISS spectrum in 2002 November and found that the nova was faint in X-rays. We then obtained a 25 ks Chandra Low Energy Transmission Grating Spectrometer (LETGS) observation on 2003 March 19. By this time, it had evolved into the supersoft X-ray phase exhibiting a continuous spectrum with deep absorption features. The light curve from the observation showed large-amplitude oscillations with a period of 1325 s (22 minutes) followed by a decline in the total count rate after ∼13 ks of observations. The count rate dropped from ∼40 counts s-1 to practically zero within ∼6 ks and stayed low for the rest of the observation (∼6 ks). The spectral hardness ratio changed from maxima to minima in correlation with the oscillations and then became significantly softer during the decay. Strong H-like and He-like lines of oxygen, nitrogen, and carbon were found in absorption during the bright phase, indicating temperatures between 1 and 2 MK, but they were shifted in wavelength corresponding to a Doppler velocity of -2400 km s-1. The spectrum obtained after the decline in count rate showed emission lines of C VI, N VI, and N VII, suggesting that we were seeing expanding gas ejected during the outburst, probably originating from CNO-cycled material. An XMM-Newton Target of Opportunity observation, obtained on 2002 April 4 and a later LETGS observation from 2003 July 18 also showed oscillations, but with smaller amplitudes.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume594
Issue number2 II
DOIs
StatePublished - Sep 10 2003

Fingerprint

light curve
spectrometer
oscillation
gratings
spectrometers
energy
x rays
outburst
oscillations
hardness
wavelength
oxygen
nitrogen
continuous spectra
carbon
XMM-Newton telescope
gas
newton
rate
temperature

Keywords

  • Novae, cataclysmic variables
  • Stars: individual (V4743 Sagittarii)
  • Stars: oscillations
  • White dwarfs
  • X-rays: binaries

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

A Chandra low energy transmission grating spectrometer observation of V4743 Sagittarii : A supersoft X-ray source and a violently variable light curve. / Ness, J. U.; Starrfield, Sumner; Burwitz, V.; Wichmann, R.; Hauschildt, P.; Drake, J. J.; Wagner, R. M.; Bond, H. E.; Krautter, J.; Orio, M.; Hernanz, M.; Gehrz, R. D.; Woodward, C. E.; Butt, Y.; Mukai, K.; Balman, S.; Truran, J. W.

In: Astrophysical Journal, Vol. 594, No. 2 II, 10.09.2003.

Research output: Contribution to journalArticle

Ness, JU, Starrfield, S, Burwitz, V, Wichmann, R, Hauschildt, P, Drake, JJ, Wagner, RM, Bond, HE, Krautter, J, Orio, M, Hernanz, M, Gehrz, RD, Woodward, CE, Butt, Y, Mukai, K, Balman, S & Truran, JW 2003, 'A Chandra low energy transmission grating spectrometer observation of V4743 Sagittarii: A supersoft X-ray source and a violently variable light curve', Astrophysical Journal, vol. 594, no. 2 II. https://doi.org/10.1086/378664
Ness, J. U. ; Starrfield, Sumner ; Burwitz, V. ; Wichmann, R. ; Hauschildt, P. ; Drake, J. J. ; Wagner, R. M. ; Bond, H. E. ; Krautter, J. ; Orio, M. ; Hernanz, M. ; Gehrz, R. D. ; Woodward, C. E. ; Butt, Y. ; Mukai, K. ; Balman, S. ; Truran, J. W. / A Chandra low energy transmission grating spectrometer observation of V4743 Sagittarii : A supersoft X-ray source and a violently variable light curve. In: Astrophysical Journal. 2003 ; Vol. 594, No. 2 II.
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abstract = "V4743 Sagittarii (Nova Sgr 2002 No. 3) was discovered on 2002 September 20. We obtained a 5 ks ACISS spectrum in 2002 November and found that the nova was faint in X-rays. We then obtained a 25 ks Chandra Low Energy Transmission Grating Spectrometer (LETGS) observation on 2003 March 19. By this time, it had evolved into the supersoft X-ray phase exhibiting a continuous spectrum with deep absorption features. The light curve from the observation showed large-amplitude oscillations with a period of 1325 s (22 minutes) followed by a decline in the total count rate after ∼13 ks of observations. The count rate dropped from ∼40 counts s-1 to practically zero within ∼6 ks and stayed low for the rest of the observation (∼6 ks). The spectral hardness ratio changed from maxima to minima in correlation with the oscillations and then became significantly softer during the decay. Strong H-like and He-like lines of oxygen, nitrogen, and carbon were found in absorption during the bright phase, indicating temperatures between 1 and 2 MK, but they were shifted in wavelength corresponding to a Doppler velocity of -2400 km s-1. The spectrum obtained after the decline in count rate showed emission lines of C VI, N VI, and N VII, suggesting that we were seeing expanding gas ejected during the outburst, probably originating from CNO-cycled material. An XMM-Newton Target of Opportunity observation, obtained on 2002 April 4 and a later LETGS observation from 2003 July 18 also showed oscillations, but with smaller amplitudes.",
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T2 - A supersoft X-ray source and a violently variable light curve

AU - Ness, J. U.

AU - Starrfield, Sumner

AU - Burwitz, V.

AU - Wichmann, R.

AU - Hauschildt, P.

AU - Drake, J. J.

AU - Wagner, R. M.

AU - Bond, H. E.

AU - Krautter, J.

AU - Orio, M.

AU - Hernanz, M.

AU - Gehrz, R. D.

AU - Woodward, C. E.

AU - Butt, Y.

AU - Mukai, K.

AU - Balman, S.

AU - Truran, J. W.

PY - 2003/9/10

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N2 - V4743 Sagittarii (Nova Sgr 2002 No. 3) was discovered on 2002 September 20. We obtained a 5 ks ACISS spectrum in 2002 November and found that the nova was faint in X-rays. We then obtained a 25 ks Chandra Low Energy Transmission Grating Spectrometer (LETGS) observation on 2003 March 19. By this time, it had evolved into the supersoft X-ray phase exhibiting a continuous spectrum with deep absorption features. The light curve from the observation showed large-amplitude oscillations with a period of 1325 s (22 minutes) followed by a decline in the total count rate after ∼13 ks of observations. The count rate dropped from ∼40 counts s-1 to practically zero within ∼6 ks and stayed low for the rest of the observation (∼6 ks). The spectral hardness ratio changed from maxima to minima in correlation with the oscillations and then became significantly softer during the decay. Strong H-like and He-like lines of oxygen, nitrogen, and carbon were found in absorption during the bright phase, indicating temperatures between 1 and 2 MK, but they were shifted in wavelength corresponding to a Doppler velocity of -2400 km s-1. The spectrum obtained after the decline in count rate showed emission lines of C VI, N VI, and N VII, suggesting that we were seeing expanding gas ejected during the outburst, probably originating from CNO-cycled material. An XMM-Newton Target of Opportunity observation, obtained on 2002 April 4 and a later LETGS observation from 2003 July 18 also showed oscillations, but with smaller amplitudes.

AB - V4743 Sagittarii (Nova Sgr 2002 No. 3) was discovered on 2002 September 20. We obtained a 5 ks ACISS spectrum in 2002 November and found that the nova was faint in X-rays. We then obtained a 25 ks Chandra Low Energy Transmission Grating Spectrometer (LETGS) observation on 2003 March 19. By this time, it had evolved into the supersoft X-ray phase exhibiting a continuous spectrum with deep absorption features. The light curve from the observation showed large-amplitude oscillations with a period of 1325 s (22 minutes) followed by a decline in the total count rate after ∼13 ks of observations. The count rate dropped from ∼40 counts s-1 to practically zero within ∼6 ks and stayed low for the rest of the observation (∼6 ks). The spectral hardness ratio changed from maxima to minima in correlation with the oscillations and then became significantly softer during the decay. Strong H-like and He-like lines of oxygen, nitrogen, and carbon were found in absorption during the bright phase, indicating temperatures between 1 and 2 MK, but they were shifted in wavelength corresponding to a Doppler velocity of -2400 km s-1. The spectrum obtained after the decline in count rate showed emission lines of C VI, N VI, and N VII, suggesting that we were seeing expanding gas ejected during the outburst, probably originating from CNO-cycled material. An XMM-Newton Target of Opportunity observation, obtained on 2002 April 4 and a later LETGS observation from 2003 July 18 also showed oscillations, but with smaller amplitudes.

KW - Novae, cataclysmic variables

KW - Stars: individual (V4743 Sagittarii)

KW - Stars: oscillations

KW - White dwarfs

KW - X-rays: binaries

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