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Full-Text Articles in Physical Sciences and Mathematics
A Multiphase Suzaku Study Of X-Rays From Τ Sco, R. Ignace, L. M. Oskinova, M. Jardine, J. P. Cassinelli, David H. Cohen, J.-F. Donati, R. H.D. Townsend, A. Ud-Doula
A Multiphase Suzaku Study Of X-Rays From Τ Sco, R. Ignace, L. M. Oskinova, M. Jardine, J. P. Cassinelli, David H. Cohen, J.-F. Donati, R. H.D. Townsend, A. Ud-Doula
Physics & Astronomy Faculty Works
We obtained relatively high signal-to-noise X-ray spectral data of the early massive star tau Sco (B0.2V) with the Suzaku X-ray Imaging Spectrometer (XIS) instrument. This source displays several unusual features that motivated our study: (1) redshifted absorption in UV P Cygni lines to approximately +250 km s(-1) suggestive of infalling gas, (2) unusually hard X-ray emission requiring hot plasma at temperatures in excess of 10 MK whereas most massive stars show relatively soft X-rays at a few MK, and (3) a complex photospheric magnetic field of open and closed field lines. In an attempt to understand the hard component better, …
Modeling Broadband X-Ray Absorption Of Massive Star Winds, M. A. Leutenegger, David H. Cohen, J. Zsargó, Erin Marie Martell , '09, James Paton Macarthur , '11, S. P. Owocki, M. Gagné, D. J. Hillier
Modeling Broadband X-Ray Absorption Of Massive Star Winds, M. A. Leutenegger, David H. Cohen, J. Zsargó, Erin Marie Martell , '09, James Paton Macarthur , '11, S. P. Owocki, M. Gagné, D. J. Hillier
Physics & Astronomy Faculty Works
We present a method for computing the net transmission of X-rays emitted by shock-heated plasma distributed throughout a partially optically thick stellar wind from a massive star. We find the transmission by an exact integration of the formal solution, assuming that the emitting plasma and absorbing plasma are mixed at a constant mass ratio above some minimum radius, below which there is assumed to be no emission. This model is more realistic than either the slab absorption associated with a corona at the base of the wind or the exospheric approximation that assumes that all observed X-rays are emitted without …
A Mass-Loss Rate Determination For Zeta Puppis From The Quantitative Analysis Of X-Ray Emission-Line Profiles, David H. Cohen, M. A. Leutenegger, Emma Edwina Wollman , '09, J. Zsargó, D. J. Hillier, R. H.D. Townsend, S. P. Owocki
A Mass-Loss Rate Determination For Zeta Puppis From The Quantitative Analysis Of X-Ray Emission-Line Profiles, David H. Cohen, M. A. Leutenegger, Emma Edwina Wollman , '09, J. Zsargó, D. J. Hillier, R. H.D. Townsend, S. P. Owocki
Physics & Astronomy Faculty Works
We fit every emission line in the high-resolution Chandra grating spectrum of. Pup with an empirical line profile model that accounts for the effects of Doppler broadening and attenuation by the bulk wind. For each of 16 lines or line complexes that can be reliably measured, we determine a best-fitting fiducial optical depth, tau(*) equivalent to kappa(M) over dot/4 pi R(*)upsilon(infinity), and place confidence limits on this parameter. These 16 lines include seven that have not previously been reported on in the literature. The extended wavelength range of these lines allows us to infer, for the first time, a clear …
Discovery Of Rotational Braking In The Magnetic Helium-Strong Star Sigma Orionis E, R. H.D. Townsend, M. E. Oksala, David H. Cohen, S. P. Owocki, A. Ud-Doula
Discovery Of Rotational Braking In The Magnetic Helium-Strong Star Sigma Orionis E, R. H.D. Townsend, M. E. Oksala, David H. Cohen, S. P. Owocki, A. Ud-Doula
Physics & Astronomy Faculty Works
We present new U-band photometry of the magnetic helium-strong star sigma Ori E, obtained over 2004-2009 using the SMARTS 0.9 m telescope at Cerro Tololo Inter-American Observatory. When combined with historical measurements, these data constrain the evolution of the star's 1.19 day rotation period over the past three decades. We are able to rule out a constant period at the p(null) = 0.05% level, and instead find that the data are well described (p(null) = 99.3%) by a period increasing linearly at a rate of 77 ms per year. This corresponds to a characteristic spin-down time of 1.34 Myr, in …
A Test Of Pre-Main-Sequence Lithium Depletion Models, Jennifer Chun Ming Yee , '07, Eric L.N. Jensen
A Test Of Pre-Main-Sequence Lithium Depletion Models, Jennifer Chun Ming Yee , '07, Eric L.N. Jensen
Physics & Astronomy Faculty Works
Despite the extensive study of lithium depletion during pre-main-sequence (PMS) contraction, studies of individual stars show discrepancies between ages determined from the Hertzsprung-Russell (H-R) diagram and ages determined from lithium depletion, indicating open questions in the PMS evolutionary models. To further test these models, we present high-resolution spectra for members of the beta Pictoris Moving Group (BPMG), which is young and nearby. We measure equivalent widths of the 6707.8 angstrom Li I line in these stars and use them to determine lithium abundances. We combine the lithium abundance with the predictions of PMS evolutionary models in order to calculate a …