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Full-Text Articles in Physical Sciences and Mathematics
X-Ray Emission-Line Profile Modeling Of O Stars: Fitting A Spherically Symmetric Analytic Wind-Shock Model To The Chandra Spectrum Of Zeta Puppis, Roban Hultman Kramer , '03, David H. Cohen, S. P. Owocki
X-Ray Emission-Line Profile Modeling Of O Stars: Fitting A Spherically Symmetric Analytic Wind-Shock Model To The Chandra Spectrum Of Zeta Puppis, Roban Hultman Kramer , '03, David H. Cohen, S. P. Owocki
Physics & Astronomy Faculty Works
X-ray emission-line profiles provide the most direct insight into the dynamics and spatial distribution of the hot, X-ray-emitting plasma above the surfaces of OB stars. The O supergiant zeta Puppis shows broad, blueshifted, and asymmetric line profiles, generally consistent with the wind-shock picture of OB star X-ray production. We model the profiles of eight lines in the Chandra HETGS spectrum of this prototypical hot star. The fitted lines indicate that the plasma is distributed throughout the wind starting close to the photosphere, that there is significantly less attenuation of the X-rays by the overlying wind than is generally supposed, and …
High-Resolution Chandra Spectroscopy Of Tau Scorpii: A Narrow-Line X-Ray Spectrum From A Hot Star, David H. Cohen, Genevieve Escande De Messières , '04, J. J. Macfarlane, N. A. Miller, J. P. Cassinelli, S. P. Owocki, D. A. Liedahl
High-Resolution Chandra Spectroscopy Of Tau Scorpii: A Narrow-Line X-Ray Spectrum From A Hot Star, David H. Cohen, Genevieve Escande De Messières , '04, J. J. Macfarlane, N. A. Miller, J. P. Cassinelli, S. P. Owocki, D. A. Liedahl
Physics & Astronomy Faculty Works
Long known to be an unusual early-type star by virtue of its hard and strong X-ray emission, tau Scorpii poses a severe challenge to the standard picture of O-star wind-shock X-ray emission. The Chandra HETGS spectrum now provides significant direct evidence that this B0.2 star does not fit this standard wind-shock framework. The many emission lines detected with the Chandra gratings are significantly narrower than what would be expected from a star with the known wind properties of tau Sco, although they are broader than the corresponding lines seen in late-type coronal sources. While line ratios are consistent with the …
X-Ray Spectral Diagnostics Of Neon Photoionization Experiments On The Z-Machine, David H. Cohen, J. J. Macfarlane, J. E. Bailey, D. A. Liedahl
X-Ray Spectral Diagnostics Of Neon Photoionization Experiments On The Z-Machine, David H. Cohen, J. J. Macfarlane, J. E. Bailey, D. A. Liedahl
Physics & Astronomy Faculty Works
We report on an initial spectroscopic study of low-density, x-ray photoionized neon with x-ray spectroscopy. These experiments, carried out on the Z-machine at Sandia, are optimized to produce a gradient-free, collisionless plasma, and to explore issues related to the rapid x-ray photoionization of relatively cold, low-density plasmas. The initial experiments used time-integrated absorption spectroscopy, backlit by the pinch radiation, to determine the ionization balance in the gas cell. Future experiments will use time-resolved spectroscopy in both absorption and emission. The emission spectra are expected to be similar to those seen from photoionized astrophysical sources, such as x-ray binaries. Indeed, in …
X-Ray Emission Line Profile Modeling Of Hot Stars, Roban Hultman Kramer , '03, Stephanie Korinne Tonnesen , '03, David H. Cohen, S. P. Owocki, A. Ud-Doula, J. J. Macfarlane
X-Ray Emission Line Profile Modeling Of Hot Stars, Roban Hultman Kramer , '03, Stephanie Korinne Tonnesen , '03, David H. Cohen, S. P. Owocki, A. Ud-Doula, J. J. Macfarlane
Physics & Astronomy Faculty Works
The launch of high-spectral-resolution x-ray telescopes (Chandra, XMM) has provided a host of new spectralline diagnostics for the astrophysics community. In this paper we discuss Doppler-broadened emission line profiles from highly supersonic outflows of massive stars. These outflows, or winds, are driven by radiation pressure and carry a tremendous amount of kinetic energy, which can be converted to x rays by shock-heating even a small fraction of the wind plasma. The unshocked, cold wind is a source of continuum opacity to the x rays generated in the shock-heated portion of the wind. Thus the emergent line profiles are affected by …
Protoplanetary Disk Mass Distribution In Young Binaries, Eric L.N. Jensen, R. L. Akeson
Protoplanetary Disk Mass Distribution In Young Binaries, Eric L.N. Jensen, R. L. Akeson
Physics & Astronomy Faculty Works
We present millimeter-wave continuum images of four wide (separations 210-800 AU), young stellar binary systems in the Taurus-Auriga star-forming region. For all four sources, the resolution of our observations is sufficient to determine the millimeter emission from each of the components. In all four systems, the primary star's disk has stronger millimeter emission than the secondary's, and in three of the four the secondary is undetected; this is consistent with predictions of recent models of binary formation by fragmentation. The primaries circumstellar disk masses inferred from these observations are comparable to those found for young single stars, confirming that the …