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Full-Text Articles in Stars, Interstellar Medium and the Galaxy
Models Of Forbidden Line Emission Profiles From Axisymmetric Stellar Winds., Richard Ignace, A. Brimeyer
Models Of Forbidden Line Emission Profiles From Axisymmetric Stellar Winds., Richard Ignace, A. Brimeyer
ETSU Faculty Works
A number of strong infrared forbidden lines have been observed in several evolved Wolf–Rayet (WR) star winds, and these are important for deriving metal abundances and testing stellar evolution models. In addition, because these optically thin lines form at large radius in the wind, their resolved profiles carry an imprint of the asymptotic structure of the wind flow. This work presents model forbidden line profile shapes formed in axisymmetric winds. It is well known that an optically thin emission line formed in a spherical wind expanding at constant velocity yields a flat-topped emission profile shape. Simulated forbidden lines are produced …
Microlensing Of Circumstellar Envelopes Iii. Line Profiles From Stellar Winds In Homologous Expansion., M. Hendry, Richard Ignace, H. Bryce
Microlensing Of Circumstellar Envelopes Iii. Line Profiles From Stellar Winds In Homologous Expansion., M. Hendry, Richard Ignace, H. Bryce
ETSU Faculty Works
This paper examines line profile evolution due to the linear expansion of circumstellar material obsverved during a microlensing event. This work extends our previous papers on emission line profile evolution from radial and azimuthal flow during point mass lens events and fold caustic crossings. Both “flavours” of microlensing were shown to provide effective diagnostics of bulk motion in circumstellar envelopes. In this work a different genre of flow is studied, namely linear homologous expansion, for both point mass lenses and fold caustic crossings. Linear expansion is of particular relevance to the effects of microlensing on supernovae at cosmological distances. We …
The Polarization Signature From Microlensing Of Circumstellar Envelopes In Caustic Cossing Events, Richard Ignace, J. Bjorkman, H. Bryce
The Polarization Signature From Microlensing Of Circumstellar Envelopes In Caustic Cossing Events, Richard Ignace, J. Bjorkman, H. Bryce
ETSU Faculty Works
In recent years, it has been shown that microlensing is a powerful tool for examining the atmospheres of stars in the Galactic bulge and Magellanic Clouds. The high gradient of magnification across the source during both small impact parameter events and caustic crossings offers a unique opportunity for determining the surface brightness profile of the source. Furthermore, models indicate that these events can also provide an appreciable polarization signal: arising from differential magnification across the otherwise symmetric source. Earlier work has addressed the signal from a scattering photosphere for both point mass lenses and caustic crossings. In a previous paper, …
First Glimpse Results On The Stellar Structure Of The Galaxy., R. Benjamin, E. Churchwell, B. Babler, R. Indebetouw, M. Meade, B. Whitney, C. Watson, M. Wolfire, M. Wolff, Richard Ignace, T. Bania, S. Bracker, D. Clemens, L. Chomiuk, M. Cohen, J. Dickey, J. Jackson, H. Kobulnicky, E. Mercer, J. Mathis, S. Stolovy, B. Uzpen
First Glimpse Results On The Stellar Structure Of The Galaxy., R. Benjamin, E. Churchwell, B. Babler, R. Indebetouw, M. Meade, B. Whitney, C. Watson, M. Wolfire, M. Wolff, Richard Ignace, T. Bania, S. Bracker, D. Clemens, L. Chomiuk, M. Cohen, J. Dickey, J. Jackson, H. Kobulnicky, E. Mercer, J. Mathis, S. Stolovy, B. Uzpen
ETSU Faculty Works
The GLIMPSE (Galactic Legacy Mid-Plane Survey Extraordinaire) Point Source Catalog of ~ 30 million mid-infrared sources towards the inner Galaxy, 10 < |l| < 65 degrees and |b| < 1 degree, was used to determine the distribution of stars in Galactic longitude, latitude, and apparent magnitude. The counts versus longitude can be approximated by the modified Bessel function N=N_0*(l/l_0)*K_1(l/l_0), where l_0 is insensitive to limiting magnitude, band choice, and side of Galactic center: l_0= 17-30 degrees with a best fit value in the the 4.5 micron band of l_0=24 +/- 4 degrees. Modeling the source distribution as an exponential disk yields a radial scale length of H= 3.9 +/- 0.6 kpc. There is a pronounced north-south asymmetry in source counts for |l| < 30 degrees, with ~ 25% more stars in the north. For l=10-30 degrees, there is a strong enhancement of stars of m= 11.5-13.5 mag. A linear bar passing through the Galactic center with half-length R_bar=4.4 +/- 0.5 kpc, tilted by phi=44 +/- 10 degrees to the Sun-Galactic Center line, provides the simplest interpretation of this data. We examine the possibility that enhanced source counts at l=26-28 degrees, 31.5-34 degrees, and 306-309 degrees are related to Galactic spiral structure. Total source counts are depressed in regions where the counts of red objects (m_K-m_[8.0] >3) peak. In these areas, the counts are reduced by extinction due to molecular gas and/or high diffuse backgrounds associated with star formation.
Optically Thick Clumps – Not The Solution To The Wolf-Rayet Wind Momentum Problem?, J. Brown, J. Cassinelli, Q. Li, A. Kholtygin, Richard Ignace
Optically Thick Clumps – Not The Solution To The Wolf-Rayet Wind Momentum Problem?, J. Brown, J. Cassinelli, Q. Li, A. Kholtygin, Richard Ignace
ETSU Faculty Works
The hot star wind momentum problem eta = M-upsiloninfinity/(L/c) much greater than 1 is revisited, and it is shown that the conventional belief, that it can be solved by a combination of clumping of the wind and multiple scattering of photons, is not self-consistent for optically thick clumps. Clumping does reduce the mass loss rate. M, and hence the momentum supply, required to generate a specified radio emission measure epsilon, while multiple scattering increases the delivery of momentum from a specified stellar luminosity L. However, in the case of thick clumps, when combined the two effects act in opposition rather …