Auroral and nebular emission lines of [S II] in the optical spectra of planetary nebulae

Keenan, F. P.; Aller, L. H.; Bell, K L; Hyung, Siek; McKenna, F. C.; Ramsbottom, Catherine

doi:10.1093/mnras/281.3.1073

Cited by 87 publications

(36 citation statements)

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“…If the average N e is derived from Table 5, excluding S iii and Ar v, a value of 4500 cm −3 is found. This is in good agreement with the N e given by Hyung & Aller (1998) and Keenan et al (1996Keenan et al ( , 1997Keenan et al ( , 1998Keenan et al ( , 1999 and therefore has been adopted to derive the T e and abundances. N e derived from S iii and Ar v differs by a large amount from the rest of the ions.…”

Section: Electron Densitysupporting

confidence: 84%

An ISO and IUE study of planetary nebula NGC 2440

Salas

Pottasch²,

Feibelman

et al. 2002

A&A

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Abstract. The infrared and ultraviolet spectra of planetary nebula NGC 2440 are presented. The observations were made by the Infrared Space Observatory (ISO) and the International Ultraviolet Explorer (IUE). These data, in conjunction with published optical observations have been used to derive electron temperature and density. The electron temperature increases with increasing ionization potential, from 11 000 to 18 000 K. The electron density has a constant value of 4500 cm −3 in agreement with previous determinations. The chemical abundance has been derived for the following elements; helium, carbon, nitrogen, oxygen, neon, sulfur and argon. The ionization correction factor turns out to be very small for all species except sulfur.

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Section: Electron Densitysupporting

confidence: 84%

An ISO and IUE study of planetary nebula NGC 2440

Salas

Pottasch²,

Feibelman

et al. 2002

A&A

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“…In order to calculate the physical conditions and the ionic oxygen abundances in these 12 H ii regions, we use the tasks available in the nebular package of iraf, originally based on the calculations of De Robertis, Dufour & Hunt (1987) and Shaw & Dufour (1995). We adopted the following atomic data: the transition probabilities of Zeippen (1982) for O + , Wiese, Fuhr & Deters (1996) and Storey & Zeippen (2000) for O ++ , Wiese et al (1996) for N + and Mendoza & Zeippen (1982) for S + ; and the effective collision strengths of Pradhan et al (2006) for O + , Aggarwal & Keenan (1999) for O ++ , Lennon & Burke (1994) for N + , and Keenan et al (1996) for S + .…”

Section: The Direct Methodsmentioning

confidence: 99%

The oxygen abundance gradient in M81 and the robustness of abundance determinations in H ii regions

Arellano-Córdova

Rodríguez

Mayya

et al. 2015

Mon. Not. R. Astron. Soc.

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We study the sensitivity of the methods available for abundance determinations in H ii regions to potential observational problems. We compare the dispersions they introduce around the oxygen and nitrogen abundance gradients when applied to five different sets of spectra of H ii regions in the galaxy M81. Our sample contains 116 H ii regions with galactocentric distances of 3 to 33 kpc, including 48 regions observed by us with the OSIRIS long-slit spectrograph at the 10.4-m Gran Telescopio Canarias telescope. The direct method can be applied to 31 regions, where we can get estimates of the electron temperature. The different methods imply oxygen abundance gradients with slopes of −0.010 to −0.002 dex kpc −1 , and dispersions in the range 0.06-0.25 dex. The direct method produces the shallowest slope and the largest dispersion, illustrating the difficulty of obtaining good estimates of the electron temperature. Three of the strong-line methods, C, ONS, and N2, are remarkably robust, with dispersions of ∼ 0.06 dex, and slopes in the range −0.008 to −0.006 dex kpc −1 . The robustness of each method can be directly related to its sensitivity to the line intensity ratios that are more difficult to measure properly. Since the results of the N2 method depend strongly on the N/O abundance ratio and on the ionization parameter, we recommend the use of the C and ONS methods when no temperature estimates are available or when they have poor quality, although the behaviour of these methods when confronted with regions that have different properties and different values of N/O should be explored.

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“…We assume that Fe and S are singly ionized and use the 16-levels model presented in Nisini et al (2002Nisini et al ( , 2005 with collisional coefficients by Nussbaumer & Storey (1988) for Fe and by Keenan et al (1996) for S. For the [Ca ]/[S ] ratio, it is assumed that no neutral calcium is present, since its ionization potential is very low, 6.1 eV. For the ionization balance we consider three limiting cases:…”

Section: Dust Contentmentioning

confidence: 99%

Relating jet structure to photometric variability: the Herbig Ae star HD 163296

Ellerbroek

Podio

Dougados

et al. 2014

A&A

131

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Herbig Ae/Be stars are intermediate-mass pre-main sequence stars surrounded by circumstellar dust disks. Some are observed to produce jets, whose appearance as a sequence of shock fronts (knots) suggests a past episodic outflow variability. This "jet fossil record" can be used to reconstruct the outflow history. We present the first optical to near-infrared (NIR) spectra of the jet from the Herbig Ae star HD 163296, obtained with VLT/X-shooter. We determine the physical conditions in the knots and also their kinematic "launch epochs". Knots are formed simultaneously on either side of the disk, with a regular interval of ∼16 yr. The velocity dispersion versus jet velocity and the energy input are comparable between both lobes. However, the mass-loss rate, velocity, and shock conditions are asymmetric. We findṀ jet /Ṁ acc ∼ 0.01−0.1, which is consistent with magneto-centrifugal jet launching models. No evidence of any dust is found in the high-velocity jet, suggesting a launch region within the sublimation radius (<0.5 au). The jet inclination measured from proper motions and radial velocities confirms that it is perpendicular to the disk. A tentative relation is found between the structure of the jet and the photometric variability of the central source. Episodes of NIR brightening were previously detected and attributed to a dusty disk wind. We report for the first time significant optical fadings lasting from a few days up to a year, coinciding with the NIR brightenings. These are very likely caused by dust lifted high above the disk plane, and this supports the disk wind scenario. The disk wind is launched at a larger radius than the high-velocity atomic jet, although their outflow variability may have a common origin. No significant relation between outflow and accretion variability could be established. Our findings confirm that this source undergoes periodic ejection events, which may be coupled with dust ejections above the disk plane.

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Auroral and nebular emission lines of [S II] in the optical spectra of planetary nebulae

Cited by 87 publications

References 0 publications

An ISO and IUE study of planetary nebula NGC 2440

An ISO and IUE study of planetary nebula NGC 2440

The oxygen abundance gradient in M81 and the robustness of abundance determinations in H ii regions

Relating jet structure to photometric variability: the Herbig Ae star HD 163296

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