A Discussion on astronomy in the ultraviolet - Preliminary results of ultraviolet interstellar extinction from TD1 satellite observations

Nandy, K.; Thompson, G. I.; Jamar, C.; Monfils, A.; Wilson, R.

doi:10.1098/rsta.1975.0067

Cited by 9 publications

(12 citation statements)

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“…For small nebulae in which the entire image falls in the entrance aperture of the IUE, we may estimate interstellar ex-1231 (24), and by Nandy et al (25). The finally adopted extinction function is that of Seaton, which agrees reasonably well with results of the other observers.…”

Section: Absiractsupporting

confidence: 80%

International Ultraviolet Explorer satellite observations of seven high-excitation planetary nebulae

Aller¹,

Keyes²

1980

Proc. Natl. Acad. Sci. U.S.A.

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Observations of seven high-excitation planetary nebulae secured with the International Ultraviolet Explorer (IUE) satellite were combined with extensive ground-based data to obtain electron densities, gas kinetic temperatures, and ionic concentrations. We then employed a network of theoretical model nebulae to estimate the factors by which observed ionic concentrations must be multiplied to obtain elemental abundances. Comparison with a large sample of nebulae for which extensive ground-based observations have been obtained shows nitrogen to be markedly enhanced in some of these objects. Possibly most, if not all, high-excitation nebulae evolve from stars that have higher masses than progenitors of nebulae of low-to-moderate excitation.

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Section: Absiractsupporting

confidence: 80%

International Ultraviolet Explorer satellite observations of seven high-excitation planetary nebulae

Aller¹,

Keyes²

1980

Proc. Natl. Acad. Sci. U.S.A.

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“…The measurements of C rad (the logarithmic extinction at Hβ determined from the radio fluxes) for a large sample of PN by Stasinska et al, on the other hand, imply R V = 2.63 (using the relations provided by Nandy et al 1975) and finally A V radio = 2.10 C rad (lower reddening for distant PN).…”

Section: Extinctionmentioning

confidence: 99%

Central stars of planetary nebulae in the Galactic bulge

Hultzsch¹,

Puls²,

Méndez

et al. 2007

A&A

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Context. Optical high-resolution spectra of five central stars of planetary nebulae (CSPN) in the Galactic bulge have been obtained with Keck/HIRES in order to derive their parameters. Since the distance of the objects is quite well known, such a method has the advantage that stellar luminosities and masses can in principle be determined without relying on theoretical relations between both quantities. Aims. By alternatively combining the results of our spectroscopic investigation with evolutionary tracks, we obtain so-called spectroscopic distances, which can be compared with the known (average) distance of the bulge-CSPN. This offers the possibility to test the validity of model atmospheres and present date post-AGB evolution. Methods. We analyze optical H/He profiles of five Galactic bulge CSPN (plus one comparison object) by means of profile fitting based on state of the art non-LTE modeling tools, to constrain their basic atmospheric parameters (T eff , log g, helium abundance and wind strength). Masses and other stellar radius dependent quantities are obtained from both the known distances and from evolutionary tracks, and the results from both approaches are compared. Results. The major result of the present investigation is that the derived spectroscopic distances depend crucially on the applied reddening law. Assuming either standard reddening or values based on radio-Hβ extinctions, we find a mean distance of 9.0 ± 1.6 kpc and 12.2 ± 2.1 kpc, respectively. An "average extinction law" leads to a distance of 10.7 ± 1.2 kpc, which is still considerably larger than the Galactic center distance of 8 kpc. In all cases, however, we find a remarkable internal agreement of the individual spectroscopic distances of our sample objects, within ±10% to ±15% for the different reddening laws. Conclusions. Due to the uncertain reddening correction, the analysis presented here cannot yet be regarded as a consistency check for our method, and a rigorous test of the CSPN evolution theory becomes only possible if this problem has been solved.

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“…This work adopts the DL-MRN interstellar grain model that was derived by fitting the observed extinction at several wavelengths with different spherical graphite particles (Mathis et al 1977;Draine & Lee 1984). Since the observed extinction shows a uniform wavelength dependence over the whole sky (Bless & Savage 1972;York et al 1973;Nandy et al 1975Nandy et al , 1976, it is reasonable to assume that the same grain population is present in the NA. Fischer et al (1994Fischer et al ( , 1996 utilize the same interstellar grain model for their simulations of protostellar envelopes.…”

Section: Density Of the Bow Shockmentioning

confidence: 99%

A peek behind the dusty curtain:K_S-band polarization photometry and bow shock models of the Galactic center source IRS 8

Rauch

Mužić

Eckart

et al. 2013

A&A

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Context. IRS 8 offers the possibility to study unique bow shock properties and polarization features in the dusty environment at the Galactic center. Aims. We aim to gain insight into the properties of the surrounding material of the bow shock source IRS 8, based on the measured polarization distribution along its extended feature. Bow shock models enable a relative positioning of its central star with respect to the northern arm and Sagittarius A*. Methods. The analysis is based on polarimetric K S -band and nonpolarimetric L -and N-band data obtained with the adaptive-optics assisted instrument NAOS/CONICA (K S -and L -band) and the mid-infrared imager/spectrograph VISIR (N-band) at the ESO Very Large Telescope. A polarization map covering an area of ∼31.9 × 8.2 at the position of IRS 8 was obtained using high-precision photometric methods, together with a polarimetric calibration specified for NACO. In addition, simulated L -band bow shock models are presented, which allow a positioning of IRS 8 with respect to the interaction medium of the northern arm.Results. This work presents interstellar dust properties for the northern arm in the vicinity of a bow shock, as well as a threedimensional positioning of IRS 8 with respect to the northern arm and Sagittarius A*. The presented polarization maps for the Galactic center source IRS 8 show a total intrinsic polarization degree of 3.3% at 13 • east of north, measured on nondeconvolved images, and 4.3% at 19 • on Lucy-Richardson deconvolved images. Analysis of the polarization distribution along the bow shock reveals a polarization pattern as it would be produced by absorption on aligned grains and shows a decreasing polarization degree towards the apex of the bow shock. Current literature provides a mean electron density for IRS 8. The comparison of this value with properties of simulated polarization maps in a circumstellar environment, which are capable of multiple scattering, leads to the conclusion that multiple scattering events reduce the degree of polarization at the apex of the bow shock. Additionally, bow shock models that allow relative positioning of IRS 8 with respect to the northern arm and Sagittarius A* are presented. The results indicate that its central star is located closer towards the observer than the northern arm.

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A Discussion on astronomy in the ultraviolet - Preliminary results of ultraviolet interstellar extinction from TD1 satellite observations

Cited by 9 publications

References 0 publications

International Ultraviolet Explorer satellite observations of seven high-excitation planetary nebulae

International Ultraviolet Explorer satellite observations of seven high-excitation planetary nebulae

Central stars of planetary nebulae in the Galactic bulge

A peek behind the dusty curtain:K_S-band polarization photometry and bow shock models of the Galactic center source IRS 8

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A Discussion on astronomy in the ultraviolet - Preliminary results of ultraviolet interstellar extinction from TD1 satellite observations

Cited by 9 publications

References 0 publications

International Ultraviolet Explorer satellite observations of seven high-excitation planetary nebulae

International Ultraviolet Explorer satellite observations of seven high-excitation planetary nebulae

Central stars of planetary nebulae in the Galactic bulge

A peek behind the dusty curtain:KS-band polarization photometry and bow shock models of the Galactic center source IRS 8

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A peek behind the dusty curtain:K_S-band polarization photometry and bow shock models of the Galactic center source IRS 8