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Optical observations of the fast nova V1674 Herculis

Neeraj Singh Rawat, L. S. Sonith, U. S. Kamath, Yash Bhargava, G. C. Anupama, Kulinder Pal Singh

Abstract

We present the evolution of optical spectra and lightcurves of the fast nova V1674 Herculis during 150 days past its eruption. Using the post-eruption AAVSO light curve, we have calculated the orbital period of V1674 Her to be 0.153 days. There is no unambiguous white dwarf spin period in our data. The optical spectra show that the ionisation increases with time. A morpho-kinematic analysis of the H$α$ line profile indicates a bipolar morphology with polar blobs and an equatorial ring. Lyman beta fluorescence is found to be the dominant mechanism for the excitation of neutral oxygen. On day 19.87, [Ne III] & [Ne V] lines are present, indicating the presence of the ONe white dwarf. On day 147.66, the nebular lines are still present, implying that the nova had not gone into quiescence yet; this spectrum is accretion-dominated.

Optical observations of the fast nova V1674 Herculis

Abstract

We present the evolution of optical spectra and lightcurves of the fast nova V1674 Herculis during 150 days past its eruption. Using the post-eruption AAVSO light curve, we have calculated the orbital period of V1674 Her to be 0.153 days. There is no unambiguous white dwarf spin period in our data. The optical spectra show that the ionisation increases with time. A morpho-kinematic analysis of the H line profile indicates a bipolar morphology with polar blobs and an equatorial ring. Lyman beta fluorescence is found to be the dominant mechanism for the excitation of neutral oxygen. On day 19.87, [Ne III] & [Ne V] lines are present, indicating the presence of the ONe white dwarf. On day 147.66, the nebular lines are still present, implying that the nova had not gone into quiescence yet; this spectrum is accretion-dominated.
Paper Structure (20 sections, 3 equations, 25 figures, 3 tables)

This paper contains 20 sections, 3 equations, 25 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Classical Novae
  3. V1674 Her: Discovery and Peculiar Characteristics
  4. Observations
  5. Photometry
  6. GIT
  7. AAVSO
  8. Spectroscopy
  9. Orbital & Spin Periodicity
  10. Spectral Evolution
  11. Early Spectra: day 1 to 6
  12. Later Spectra: day 20 to 148
  13. Observed emission lines in V1674 Her
  14. Hydrogen Lines
  15. Helium Lines
  16. ...and 5 more sections

Figures (25)

  • Figure 1: Light curve of nova V1674 Her in the GIT g$^\prime$, r$^\prime$, i$^\prime$ and z$^\prime$ bands. Offset has been applied for individual bands except i$^\prime$ band for better representation. Insets show the high cadence observations.
  • Figure 2: AAVSO V-band light curve of V1674 Her with the epochs of our spectroscopic observations marked by arrows.
  • Figure 3: LS periodogram of V1674 Her for searching the orbital period in AAVSO V and CV bands. Both V and CV bands show a clear peak at $\sim0.153$ days, as shown by the dashed line.
  • Figure 4: Phase folded light curve of V1674 Her in AAVSO V, CV and GIT r$^\prime$ bands. The lightcurves are folded at the period seen in Figure \ref{['fig:lsp_aavso']}. The GIT lightcurves also show the orbital variation but due to a lack of sufficient sampling, the sole GIT observations are unable to constrain the orbital period.
  • Figure 5: Spectral evolution of V1674 Her across eight epochs. Each epoch is labelled on the right side of the plot. The spectra have been given an offset for clarity. On the y-axis, the logarithm of flux is displayed, while the x-axis represents the wavelength. The logarithmic scale has been used to emphasise the visibility of weaker features.
  • ...and 20 more figures