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

Williams, Robert E.

doi:10.1088/0004-6256/144/4/98

Cited by 71 publications

(75 citation statements)

References 37 publications

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“…We use measurements of the [O III] lines to find Shore et al 2016). We also use the O I lines measured on day +45-permitted transitions at 7774 and 8446 Å, and the forbidden transition at 6300 Å-to constrain the column density (for at least some portions) of the ejecta Williams 2012; see Appendix C for detailed calculations). If we assume a temperature of T e =10,000 K, the O I ratios are consistent with density…”

Section: Spectroscopic Evolutionmentioning

confidence: 99%

“…The strong O I emission at 7774 and 8446 Åfrom the Magellan/MIKE spectrum-seen in Figure 10-suggests a high density of the emitting material, as the relative strength of the line at 7774 Åcompared to 8446 Åis a measure of the rate of collisional de-excitation (Williams 1994(Williams , 2012. As 8446 Åis a fluorescent line, it should be substantially more dominant than all other O I lines; the only way for 7774 Åto even approach the strength of 8446 Åis if there are very high electron densities, such as at a radiative shock front.…”

Section: Appendix C O I Density Constraintsmentioning

confidence: 99%

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A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray-luminous Classical Nova to Date

Finzell

Chomiuk

Metzger

et al. 2018

ApJ

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It has recently been discovered that some, if not all, classical novae emit GeV gamma-rays during outburst, but the mechanisms involved in the production ofgamma-rays are still not well understood. We present here a comprehensive multiwavelength data set-from radio to X-rays-for the most gamma-ray-luminous classical nova to date, V1324 Sco. Using this data set, we show that V1324 Sco is a canonical dusty Fe II-type nova, with a maximum ejecta velocity of 2600 km s −1 and an ejecta mass of a few´-10 5  M . There is also evidence for complex shock interactions, including a double-peaked radio light curve which shows high brightness temperatures at early times. To explore why V1324Sco was so gamma-ray luminous, we present a model of the nova ejecta featuring strong internal shocks and find that higher gamma-ray luminosities result from higher ejecta velocities and/or mass-loss rates. Comparison of V1324Sco with other gamma-ray-detected novae does not show clear signatures of either, and we conclude that a larger sample of similarly well-observed novae is needed to understand the origin and variation of gamma-rays in novae.

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Section: Spectroscopic Evolutionmentioning

confidence: 99%

Section: Appendix C O I Density Constraintsmentioning

confidence: 99%

A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray-luminous Classical Nova to Date

Finzell

Chomiuk

Metzger

et al. 2018

ApJ

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“…This is a major difference in the optical and infrared behavior and a significant finding from this work. This adds complexity to any unification scheme (Williams 2012;Shore 2013) that tries to explain Fe II, He/N and hybrid novae simultaneously.…”

Section: Spectral Classificationmentioning

confidence: 99%

“…In the paradigm proposed by Williams (2012), the the He/N spectra have their origin in the material lost from the white dwarf surface during the thermonuclear runaway. That is why the He lines, responsible jointly with N lines for the creation of the He/N tag, are only seen immediately after the outburst before the He-rich nova ejecta material intermingles with a large circumbinary envelope of gas whose origin is the secondary star.…”

Section: Spectral Classificationmentioning

confidence: 99%

Near-infrared studies of V5558 Sgr: an unusually slow nova with multiple outbursts

Das

Banerjee

Nandi

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We present near-infrared (1-2.5 µm) JHK photo-spectroscopic results of the unusually slow nova V5558 Sgr (2007). V5558 Sgr showed a slow climb to maximum that lasted for about 60 days and then underwent at least five strong secondary outbursts. We have analyzed the optical light curve to derive large t 2 and t 3 values of 281 ± 3 and 473 ± 3 days respectively. An alternate approach is adopted to derive a distance estimate of 1.55 ± 0.25 kpc as conventional MMRD relation may not be applicable for a slow nova. In the pre-maxima stage the spectra showed narrow (FWHM ∼ 400 -550 km s −1 ) and strong emission lines of Paschen and Brackett series with prominent P-Cygni components. In the later phase the spectra show significant changes with the development of strong and broad (∼ 1000 km s −1 ) emission lines of HI, HeI, OI, and NI and some uncommon Fe II emission lines. No evidence of dust formation is seen. V5558 Sgr has been shown to be a rare hybrid nova showing a transition from He/N to Fe II type from optical spectra. However the near-infrared data do not show such a transition and we discuss this anomalous behavior. A recombination analysis of the Brackett lines allows us to constrain the electron density and emission measure during the early optically thick phase and to estimate the mass of the ejecta to be (6.0 ± 1.5) × 10 −4 M ⊙ , assuming a filling factor of unity, from later observations.

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“…In addition to the photometric classification various approaches have been taken to classify the spectral evolution of novae (McLaughlin 1944;Gaposchkin 1957;Williams 2012). Post-outburst spectra are divided into two spectroscopic classes: the Fe ii type novae which show numerous narrow Fe ii emission lines with P Cygni profiles and He/N type novae which show broad He, N and H emission lines.…”

Section: Introductionmentioning

confidence: 99%

V5852 Sgr: an unusual nova possibly associated with the Sagittarius stream

Aydi

Mróz²,

Whitelock

et al. 2016

Mon. Not. R. Astron. Soc.

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We report spectroscopic and photometric follow-up of the peculiar nova V5852 Sgr (discovered as OGLE-2015-NOVA-01), which exhibits a combination of features from different nova classes. The photometry shows a flat-topped light curve with quasiperiodic oscillations, then a smooth decline followed by two fainter recoveries in brightness. Spectroscopy with the Southern African Large Telescope shows first a classical nova with an Fe ii or Fe ii b spectral type. In the later spectrum, broad emissions from helium, nitrogen and oxygen are prominent and the iron has faded which could be an indication to the start of the nebular phase. The line widths suggest ejection velocities around 1000 km s −1 . The nova is in the direction of the Galactic bulge and is heavily reddened by an uncertain amount. The V magnitude 16 days after maximum enables a distance to be estimated and this suggests that the nova may be in the extreme trailing stream of the Sagittarius dwarf spheroidal galaxy. If so it is the first nova to be detected from that, or from any dwarf spheroidal galaxy. Given the uncertainty of the method and the unusual light curve we cannot rule out the possibility that it is in the bulge or even the Galactic disk behind the bulge.

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

Cited by 71 publications

References 37 publications

A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray-luminous Classical Nova to Date

A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray-luminous Classical Nova to Date

Near-infrared studies of V5558 Sgr: an unusually slow nova with multiple outbursts

V5852 Sgr: an unusual nova possibly associated with the Sagittarius stream

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