Neutral Oxygen in Stellar Atmospheres.

Keenan, Philip C.; Hynek, J. A.

doi:10.1086/145231

Cited by 28 publications

(18 citation statements)

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“…It can display absorption components because its lower level leads to the ground state through an intercombination transition. In contrast, RMT triplet (4) (centered around λ8446), is mainly produced by optically thick H Lyβ transition that pumps the upper level of the OI λ1025 and, by cascade, populates the upper level of the λ8446 triplet (Keenan and Hynek 1950) in combination with an optically thick O I λ1302 (which is responsible of the overpopulation of the lower level 3 S of the triplet and explains the occasionally strong ab-sorption component). Neutral oxygen has nearly the same ionization potential energy as H (∼13 eV) and the ∼ λ7774 triplet has a similar profile to the Balmer lines (see Fig.8 where the triplet is plotted together with the Hδ transitions, top panel).…”

Section: The High Resolution Uves Spectramentioning

confidence: 99%

The ambiguous transient ASASSN-17hx

Mason

Shore

Kuin

et al. 2020

A&A

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Section: The High Resolution Uves Spectramentioning

confidence: 99%

The ambiguous transient ASASSN-17hx

Mason

Shore

Kuin

et al. 2020

A&A

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“…The likely cause of this difference is resonant excitation of the O i 3 D level from the ground state by Lyβ photons (the excitation wavelength is 1025.77 Å compared to 1025.72 Å for Lyβ). This excitation is followed by downward transitions that populate the 3 P states, which subsequently produce the O i λ8446 triplet (Keenan & Hynek 1950). This process does not populate the 5 P state that is responsible for the O i λ7774 lines.…”

Section: Additional Absorption and Emission Linesmentioning

confidence: 99%

An Intermediate Luminosity Transient in NGC 300: The Eruption of a Dust-Enshrouded Massive Star

Berger

Söderberg

Chevalier

et al. 2009

ApJ

139

246

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We present multi-epoch high-resolution optical spectroscopy, UV/radio/X-ray imaging, and archival Hubble and Spitzer observations of an intermediate luminosity optical transient recently discovered in the nearby galaxy NGC 300. We find that the transient (NGC 300 OT2008-1) has a peak absolute magnitude of M bol ≈ −11.8 mag, intermediate between novae and supernovae, and similar to the recent events M85 OT2006-1 and SN 2008S. Our high-resolution spectra, the first for this event, are dominated by intermediate velocity (∼200-1000 km s −1 ) hydrogen Balmer lines and Ca ii emission and absorption lines that point to a complex circumstellar environment, reminiscent of the yellow hypergiant IRC+10420. In particular, we detect asymmetric Ca ii H&K absorption with a broad red wing extending to ∼10 3 km s −1 , indicative of gas inflow at high velocity (possibly the wind of a massive binary companion). The low luminosity, intermediate velocities, and overall similarity to a known eruptive star indicate that the event did not result in a complete disruption of the progenitor. We identify the progenitor in archival Spitzer observations, with deep upper limits from Hubble data. The spectral energy distribution points to a dustenshrouded star with a luminosity of about 6 × 10 4 L , indicative of a ∼10-20 M progenitor (or binary system). This conclusion is in good agreement with our interpretation of the outburst and circumstellar properties. The lack of significant extinction in the transient spectrum indicates that the dust surrounding the progenitor was cleared by the outburst. We thus predict that the progenitor should be eventually visible with Hubble if the transient event marks an evolutionary transition to a dust-free state, or with Spitzer if the event marks a cyclical process of dust formation.

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“…The oxygen O i 7771–4 Å triplet has been known as a luminosity indicator in supergiants for a long time (see Merrill 1925; Keenan & Hynek 1950). Using the photoelectric technique on the sample of 10 F0–F8 supergiants with known luminosities (which in eight cases were obtained from the distances to the parent clusters), Osmer (1972) and Baker (1974) derived the first quantitative relations between the strength of the triplet and the absolute magnitude ( M v ).…”

Section: Introductionmentioning

confidence: 99%

Accurate luminosities from the oxygen λ7771-4 Å triplet and the fundamental parameters of F-G supergiants

Kovtyukh¹,

Gorlova²,

Belik³

2012

Monthly Notices of the Royal Astronomical Society

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The oxygen λ7771–4 Å triplet is a good indicator of luminosity in A–G supergiants. However, its strength also depends on other atmospheric parameters. In this study, we present the luminosity calibrations where, for the first time, the effects of the effective temperature, microturbulent velocity, surface gravity and the abundance have been disentangled. The calibrations are derived on the basis of a data set of high‐dispersion spectra of 60 yellow supergiants with highly reliable luminosities and accurate atmospheric parameters. This allowed us to bring the uncertainty of the triplet‐based absolute magnitudes down to 0.26 mag. The calibrations are suitable for spectral types F0–K0 and luminosity classes I–II, covering absolute magnitudes Mv from −1.0 to −10 mag.

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Neutral Oxygen in Stellar Atmospheres.

Cited by 28 publications

References 0 publications

The ambiguous transient ASASSN-17hx

The ambiguous transient ASASSN-17hx

An Intermediate Luminosity Transient in NGC 300: The Eruption of a Dust-Enshrouded Massive Star

Accurate luminosities from the oxygen λ7771-4 Å triplet and the fundamental parameters of F-G supergiants

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