30 research outputs found
The Otterbein Miscellany - Spring 1985
https://digitalcommons.otterbein.edu/miscellany/1010/thumbnail.jp
The interactions of winds from massive young stellar objects: X-ray emission, dynamics, and cavity evolution
2D axis-symmetric hydrodynamical simulations are presented which explore the
interaction of stellar and disk winds with surrounding infalling cloud
material. The star, and its accompanying disk, blow winds inside a cavity
cleared out by an earlier jet. The collision of the winds with their
surroundings generates shock heated plasma which reaches temperatures up to
~10^8 K. Attenuated X-ray spectra are calculated from solving the equation of
radiative transfer along lines-of-sight. This process is repeated at various
epochs throughout the simulations to examine the evolution of the intrinsic and
attenuated flux. We find that the dynamic nature of the wind-cavity interaction
fuels intrinsic variability in the observed emission on timescales of several
hundred years. This is principally due to variations in the position of the
reverse shock which is influenced by changes in the shape of the cavity wall.
The collision of the winds with the cavity wall can cause clumps of cloud
material to be stripped away. Mixing of these clumps into the winds mass-loads
the flow and enhances the X-ray emission measure. The position and shape of the
reverse shock plays a key role in determining the strength and hardness of the
X-ray emission. In some models the reverse shock is oblique to much of the
stellar and disk outflows, whereas in others it is closely normal over a wide
range of polar angles. For reasonable stellar and disk wind parameters the
integrated count rate and spatial extent of the intensity peak for X-ray
emission agree with \textit{Chandra} observations of the deeply embedded MYSOs
S106 IRS4, Mon R2 IRS3 A, and AFGL 2591.(abridged)Comment: 19 pages, 14 figures, accepted for publication in MNRA
Large enhancement of deuteron polarization with frequency modulated microwaves
We report a large enhancement of 1.7 in deuteron polarization up to values of
0.6 due to frequency modulation of the polarizing microwaves in a two liters
polarized target using the method of dynamic nuclear polarization. This target
was used during a deep inelastic polarized muon-deuteron scattering experiment
at CERN. Measurements of the electron paramagnetic resonance absorption spectra
show that frequency modulation gives rise to additional microwave absorption in
the spectral wings. Although these results are not understood theoretically,
they may provide a useful testing ground for the deeper understanding of
dynamic nuclear polarization.Comment: 10 pages, including the figures coming in uuencoded compressed tar
files in poltar.uu, which also brings cernart.sty and crna12.sty files neede
Dense gas and the nature of the outflows
We present the results of the observations of the (J,K)=(1,1) and the
(J,K)=(2,2) inversion transitions of the NH3 molecule toward a large sample of
40 regions with molecular or optical outflows, using the 37 m radio telescope
of the Haystack Observatory. We detected NH3 emission in 27 of the observed
regions, which we mapped in 25 of them. Additionally, we searched for the
6{16}-5{23} H2O maser line toward six regions, detecting H2O maser emission in
two of them, HH265 and AFGL 5173. We estimate the physical parameters of the
regions mapped in NH3 and analyze for each particular region the distribution
of high density gas and its relationship with the presence of young stellar
objects. From the global analysis of our data we find that in general the
highest values of the line width are obtained for the regions with the highest
values of mass and kinetic temperature. We also found a correlation between the
nonthermal line width and the bolometric luminosity of the sources, and between
the mass of the core and the bolometric luminosity. We confirm with a larger
sample of regions the conclusion of Anglada et al. (1997) that the NH3 line
emission is more intense toward molecular outflow sources than toward sources
with optical outflow, suggesting a possible evolutionary scheme in which young
stellar objects associated with molecular outflows progressively lose their
neighboring high-density gas, weakening both the NH3 emission and the molecular
outflow in the process, and making optical jets more easily detectable as the
total amount of gas decreases.Comment: 27 pages, 37 figures. Accepted for publication in Astronomy and
Astrophysics. Abstract is abridge