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Articles
Thesis
Talks and displays
Journal Articles
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 H. Kramer, David H. Cohen, Stanley P. Owocki
accepted by ApJ, March 2003
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 that there is not a
strong trend in wind absorption with wavelength.
X ray emission line profile modeling of hot stars
Roban H. Kramer, Stephanie K. Tonnesen, David H. Cohen, Stanley P. Owocki, Asif ud-Doula, Joseph J. MacFarlane
to appear in Review of Scientific Instruments, March 2003
Senior Thesis, Swarthmore College 2003
Modeling O-Star X-Ray Emission-Line Profiles:
Fitting a Parameterized, Spherically-Symmetric Wind Model to
Chandra Spectra
Roban H. Kramer, advisor David H. Cohen
X-ray emission from hot (O- and B-type) stars is a long-standing
astrophysical puzzle. High-resolution x-ray spectroscopy of hot stars
resolves emission line profile shapes, offering direct insight into
the dynamics and spatial distribution of the x-ray-emitting
plasma. 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. Here, for the first time, this is
demonstrated quantitatively by fitting a spherically-symmetric
phenomenological wind model to a Chandra spectrum of zeta
Puppis. The results of the fits to eight lines are presented
here. Statistically good fits to seven of the lines are achieved, with
extracted parameters providing constraints on the amount of absorption
in the wind and the minimum radius of x-ray emission. The results
indicate that a modest amount of wind attenuation is required, which
is inconsistent with previous theoretical calculations of continuum
optical depths. The implications of these results are discussed in
light of other recent observational and theoretical work.
Recent Talks and Displays
X-ray Emission Line Profile Modeling of O stars: zeta Puppis as a Wind-Shock Source
Roban H. Kramer
Display at AAS 201st meeting, Januray 9, 2003, Seattle, WA
Undergraduate Research at Liberal Arts Colleges
Roban H. Kramer
Oral presentation at special session on undergraduate research
AAS 201st meeting, Januray 6, 2003, Seattle, WA
Articles | Talks and displays
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