The Ultraviolet Spectrum of AG Draconis

Altamore, A.; Baratta, G. B.; Cassatella, A.; Giangrande, A.; Ponz, D.; Ricciardi, O.; Viotti, R.

doi:10.1007/978-94-009-7834-8_32

Cited by 5 publications

(7 citation statements)

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“…The total visual extinction, A v , is assumed to be the same in each case and, for convenience, is set to zero. Altamore et al (1979) argue that the strength of the À2200 diffuse feature is the best indicator of color excess from which they derive a value of E(B -V) = 0.25 for HD 200775. The remaining 0.31 magnitude they ascribe to an intrinsic reddening caused by emission from an extensive shell.…”

Section: Discussionmentioning

confidence: 99%

The extinction of HD 200775 by dust in NGC 7023

Walker

Yang

Witt

et al. 1980

PASP

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HD 200775 is obscured by the dust of the bright reflection nebula NGC 7023. In ground-based Reticon spectra between ÀÀ5500 and 6800 the diffuse interstellar features are extremely weak and curvature, or very broad-band structure, in the extinction curve is significantly less than for other stars.The UV extinction curve has been generated from IUE spectra between ÀA1250 and 3200. The À2175 absorption is weak and the À1540 feature found by Nandy et al. (1976) is absent, which resembles the case of 6 1 Ori, but the marked rise in extinction for À -1 > 6jU, _1 is typical of the 'average' extinction curve. Differences between the extinction curve for HD 200775 and the 'average' curve and that for 0 1 Ori give profiles of the À2175 + À1540 features, and the rapid increase in UV extinction, respectively. It is suggested that a three-component dust model is necessary to explain these observations: fine grains for the UV extinction, large grains for the optical region, and a third component, possibly a volatile mantle which is responsible for the diffuse absorption features and the very broad-band structure.

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Section: Discussionmentioning

confidence: 99%

The extinction of HD 200775 by dust in NGC 7023

Walker

Yang

Witt

et al. 1980

PASP

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“…Previous work on line identifications in ultraviolet spectra of objects with both a cool and a hot component include work on the Aurigae binary system 31 Cyg ( Bauer & Stencel 1989), the M1-2 Iab + B system KQ Pup (Altamore et al 1982;Redfors & Johansson 2000), and the symbiotic star RR Tel (Penston et al 1983;Hartman & Johansson 2000). Hartman & Johansson (2000) show that the majority of the Fe ii lines in the spectrum of RR Tel come from only certain particular levels and can be explained by fluorescence processes (photoionization by accidental resonance, or PAR).…”

Section: Line Identification Proceduresmentioning

confidence: 98%

An Ultraviolet Spectral Atlas of VV Cephei during Total Eclipse

Bauer

Bennett

Brown

2007

ASTROPHYS J SUPPL S

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The first observations of the ultraviolet spectrum of the binary system VV Cep (M2 Iab + B?) during total eclipse have been made with the HST. A rich emission-line spectrum is seen, with over two thousand emission features present. Shortward of 1600 8, a weak continuum presumably due to Rayleigh scattering of the hot component is present, strengthening markedly shortward of 1500 8. The continuum of the M supergiant becomes apparent longward of 2650 8. Numerous circumstellar and interstellar absorption features are also seen. We present an atlas of the spectrum from 1300Y3160 8 as observed near midtotality and at two epochs closer to egress, when gas surrounding the hot component has begun to emerge from eclipse and the flux on the short-wavelength edges of many emission lines has increased. This atlas has been annotated with line identifications. The majority of the emission lines arise from singly ionized elements in the iron group with upper levels up to 14 eV, and generally correspond to absorption features seen out of eclipse. Circumstellar and interstellar absorption features seen out of eclipse remain in absorption during totality and are also annotated on the atlas. Well over 90% of the emission features have plausible identifications, but there are many blends. Only a few hundred features appear to be free enough from blending for useful measurement of the peak flux in the line. We present a list of these unblended features.

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“…The driving source of NGC 7023 is the massive binary system HD 200775 of B3Ve-B5 spectral type, which has been extensively studied (e.g. Racine 1968;Altamore et al 1980;Finkenzeller 1985;Pogodin et al 2004;Witt et al 2006;Alecian et al 2008) with a recently detected protoplanetary disc (Okamoto et al 2009;?). The Hipparcos parallax distance to HD 200775 is estimated to be 520 +180 −110 pc (van Leeuwen 2007).…”

Section: Introductionmentioning

confidence: 99%

Physical structure of the photodissociation regions in NGC 7023

Koehler

Habart

Arab

et al. 2014

A&A

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Context. The determination of the physical conditions in molecular clouds is a key step towards our understanding of their formation and evolution of associated star formation. We investigate the density, temperature, and column density of both dust and gas in the photodissociation regions (PDRs) located at the interface between the atomic and cold molecular gas of the NGC 7023 reflection nebula. We study how young stars affect the gas and dust in their environment. Aims. Several Herschel Space Telescope programs provide a wealth of spatial and spectral information of dust and gas in the heart of PDRs. We focus our study on Spectral and Photometric Image Receiver (SPIRE) Fourier-Transform Spectrometer (FTS) fully sampled maps that allow us for the first time to study the bulk of cool/warm dust and warm molecular gas (CO) together. In particular, we investigate if these populations spatially coincide, if and how the medium is structured, and if strong density and temperature gradients occur, within the limits of the spatial resolution obtained with Herschel. Methods. The SPIRE FTS fully sampled maps at different wavelengths are analysed towards the northwest (NW) and the east (E) PDRs in NGC 7023. We study the spatial and spectral energy distribution of a wealth of intermediate rotational 12 CO 4 ≤ J u ≤ 13 and 13 CO 5 ≤ J u ≤ 10 lines. A radiative transfer code is used to assess the gas kinetic temperature, density, and column density at different positions in the cloud. The dust continuum emission including Spitzer, the Photoconductor Array Camera and Spectrometer (PACS), and SPIRE photometric and the Institute for Radio Astronomy in the Millimeter Range (IRAM) telescope data is also analysed. Using a single modified black body and a radiative transfer model, we derive the dust temperature, density, and column density. Results. The cloud is highly inhomogeneous, containing several irradiated dense structures. Excited 12 CO and 13 CO lines and warm dust grains localised at the edge of the dense structures reveal high column densities of warm/cool dense matter. Both tracers give a good agreement in the local density, column density, and physical extent, leading to the conclusion that they trace the same regions. The derived density profiles show a steep gradient at the cloud edge reaching a maximum gas density of 10 5 −10 6 cm −3 in the PDR NGC 7023 NW and 10 4 −10 5 cm −3 in the PDR NGC 7023 E and a subsequent decrease inside the cloud. Close to the PDR edges, the dust temperature (30 K and 20 K for the NW and E PDRs, respectively) is lower than the gas temperature derived from CO lines (65−130 K and 45−55 K, respectively). Further inside the cloud, the dust and gas temperatures are similar. The derived thermal pressure is about 10 times higher in NGC 7023 NW than in NGC 7023 E. Comparing the physical conditions to the positions of known young stellar object candidates in NGC 7023 NW, we find that protostars seem to be spatially correlated with the dense structures. Conclusions. Our approach combining bo...

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The Ultraviolet Spectrum of AG Draconis

Cited by 5 publications

References 0 publications

The extinction of HD 200775 by dust in NGC 7023

The extinction of HD 200775 by dust in NGC 7023

An Ultraviolet Spectral Atlas of VV Cephei during Total Eclipse

Physical structure of the photodissociation regions in NGC 7023

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