The total‐to‐selective extinction ratio determined from near IR photometry of OB stars

Wegner, W.

doi:10.1002/asna.200310081

Cited by 57 publications

(56 citation statements)

References 26 publications

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“…(1) Valencic et al (2004); (2) Gordon et al (2009); (3) Jenniskens & Greenberg (1993); (4) Lewis et al (2005); (5) Wegner et al (2003); (6) Sofia et al (2004); (7) Gnacinski & Sikorski (1999); (8) Cardelli et al (1989); (9) Rachford et al (2008).…”

Section: Resultsunclassified

Interstellar Silicon Depletion and the Ultraviolet Extinction

Mishra

2017

ApJ

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Spinning small silicate grains were recently invoked to account for the Galactic foreground anomalous microwave emission. These grains, if present, will absorb starlight in the far ultraviolet (UV). There is also renewed interest in attributing the enigmatic 2175Å interstellar extinction bump to small silicates. To probe the role of silicon in the UV extinction, we explore the relations between the amount of silicon required to be locked up in silicates [Si/H] dust and the 2175Å bump or the far-UV extinction rise, based on an analysis of the extinction curves along 46 Galactic sightlines for which the gas-phase silicon abundance [Si/H]

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Section: Resultsunclassified

Interstellar Silicon Depletion and the Ultraviolet Extinction

Mishra

2017

ApJ

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“…+20 −1 (H i opacity)] × 10 20 cm −2 mag −1 . Assuming a standard total-to-selective extinction ratio R V = A V /E(B − V) = 3.10 (Wegner 2003), the dust-to-gas ratio just estimated appears to be ∼50% higher than the average value in the diffuse ISM, N(H)/E(B − V) = 58 × 10 20 cm −2 mag −1 (Bohlin et al 1978), and a factor of three higher than what is inferred for the dark phase in local clouds from γ-ray measurements, N(H)/E(B − V) 30 × 10 20 cm −2 mag −1 (Grenier et al 2005;Abdo et al 2010f). The discrepancy is confirmed by the extinction data.…”

Section: Dark Neutral Gasmentioning

confidence: 99%

The cosmic-ray and gas content of the Cygnus region as measured inγ-rays by theFermiLarge Area Telescope

Ackermann¹,

Ajello²,

Allafort³

et al. 2012

A&A

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Context. The Cygnus region hosts a giant molecular-cloud complex that actively forms massive stars. Interactions of cosmic rays with interstellar gas and radiation fields make it shine at γ-ray energies. Several γ-ray pulsars and other energetic sources are seen in this direction. Aims. In this paper we analyze the γ-ray emission measured by the Fermi Large Area Telescope (LAT) in the energy range from 100 MeV to 100 GeV in order to probe the gas and cosmic-ray content on the scale of the whole Cygnus complex. The γ-ray emission on the scale of the central massive stellar clusters and from individual sources is addressed elsewhere. Methods. The signal from bright pulsars is greatly reduced by selecting photons in their off-pulse phase intervals. We compare the diffuse γ-ray emission with interstellar gas maps derived from radio/mm-wave lines and visual extinction data. A general model of the region, including other pulsars and γ-ray sources, is sought. Results. The integral H i emissivity above 100 MeV averaged over the whole Cygnus complex amounts to [2.06 ± 0.11 (stat.), where the systematic error is dominated by the uncertainty on the H i opacity to calculate its column densities. The integral emissivity and its spectral energy distribution are both consistent within the systematics with LAT measurements in the interstellar space near the solar system. The average X CO = N(H 2 )/W CO ratio is found to be [1.68 ± 0.05 (stat.) (K km s −1 ) −1 , consistent with other LAT measurements in the Local Arm. We detect significant γ-ray emission from dark neutral gas for a mass corresponding to ∼40% of what is traced by CO. The total interstellar mass in the Cygnus complex inferred from its γ-ray emission amounts to 8 +5 −1 × 10 6 M at a distance of 1.4 kpc. Conclusions. Despite the conspicuous star formation activity and high masses of the interstellar clouds, the cosmic-ray population in the Cygnus complex averaged over a few hundred parsecs is similar to that of the local interstellar space.

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“…The observed far-UV fluxes were corrected using the extinction curve k λ of Cardelli et al (1989) and the ratio of total to selective extinction R = 3.1 (e.g. Wegner 2003). In addition to the attenuation effects included in Eq.…”

Section: The Hot Star Continuummentioning

confidence: 99%

The origin of the supersoft X-ray-optical/UV flux anticorrelation in the symbiotic binary AG Draconis

Skopal¹,

Sekeráš²,

González‐Riestra

et al. 2009

A&A

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Context. AG Draconis produces a strong supersoft X-ray emission. The X-ray and optical/UV fluxes are in strict anticorrelation throughout the active and quiescent phases. Aims. We identify the source of the X-ray emission and reveal the nature of the observed flux anticorrelation. Methods. We used X-ray and UV observations with XMM-Newton, far-UV spectroscopy from FUSE, low-and high-resolution IUE spectra, and optical/near-IR spectroscopic and/or photometric observations. We modeled the spectral energy distribution and broad wings of the O vi λ1032, λ1038 and He ii λ1640 lines by the electron-scattering during the maximum of the 2003 burst, and the subsequent transition and quiescent phase. Results. The X-ray-near-IR energy distribution at different levels of the star's brightness confirmed the observed flux anticorrelation quantitatively and showed that the optical bursts are associated to an increase in the nebular component of radiation. The profile-fitting analysis revealed a significant increase in the mean particle density around the hot star from ∼2.6 × 10 10 cm −3 during quiescent phase to ∼1.1 × 10 12 cm −3 during the burst. Conclusions. The supersoft X-ray emission is produced by the white dwarf photosphere. The X-ray and far-UV fluxes make it possible to determine its temperature unambiguously. The supersoft X-ray-optical/UV flux anticorrelation is caused by the variable wind from the hot star. The enhanced hot star wind gives rise to the optical bursts by reprocessing high-energy photons from the Lyman continuum to the optical/UV.

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The total‐to‐selective extinction ratio determined from near IR photometry of OB stars

Cited by 57 publications

References 26 publications

Interstellar Silicon Depletion and the Ultraviolet Extinction

Interstellar Silicon Depletion and the Ultraviolet Extinction

The cosmic-ray and gas content of the Cygnus region as measured inγ-rays by theFermiLarge Area Telescope

The origin of the supersoft X-ray-optical/UV flux anticorrelation in the symbiotic binary AG Draconis

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