8,371 research outputs found
A Spectroscopic Method to Measure Macho Proper Motions
A Massive Compact Halo Object (Macho) that lenses a background star will
magnify different parts of the rotating stellar disk by varying amounts. The
differential magnification will cause a shift in the centroid of the star's
spectral lines during the lensing event. The shift is proportional to the ratio
of the stellar radius to the projected separation of the Macho from the star.
It therefore provides a direct measure of the Einstein ring radius, and so also
a measure of the Macho's proper motion (angular speed). This measurement can
remove some of the degeneracy between mass, distance to the lens, and
transverse velocity that exists in the interpretation of results from ongoing
microlensing experiments, and is an independent test of the lensing nature of
the event. We show that using the high precision attainable by stellar radial
velocity measurements, it is possible to measure proper motions for
of Machos that lens A-stars in the Large Magellanic Cloud (LMC), i.e.\ of the type of relatively high-magnification events that have been
reported to date. If this proper-motion measurement were combined with a
parallax measurement of the ``reduced velocity'', then the Macho mass,
distance, speed, and direction could each be separately determined. The shift
can be measured for of the A-star events generated by Machos in the
dark halo of the LMC. This in turn would provide a measurement of the fraction
of LMC vs. Galactic Macho events.Comment: 16 pages, LaTex, two PostScript figures, OSU-TA-1/9
Nonequilibrium Shock Front Rotational, Vibrational and Electronic Temperature Measurements
Spectroscopic method for taking nonequilibrium shock front rotational, vibrational, and electronic temperature measurements in relaxation zon
Analysis of a Very Massive DA White Dwarf via the Trigonometric Parallax and Spectroscopic Methods
By two different methods, we show that LHS 4033 is an extremely massive white
dwarf near its likely upper mass limit for destruction by unstable electron
captures. From the accurate trigonometric parallax reported herein, the
effective temperature (T=10,900 K) and the stellar radius (R=0.00368 R_sun) are
directly determined from the broad-band spectral energy distribution -- the
parallax method. The effective temperature and surface gravity are also
estimated independently from the simultaneous fitting of the observed Balmer
line profiles with those predicted from pure-hydrogen model atmospheres -- the
spectroscopic method (T=10,760 K, log g=9.46). The mass of LHS 4033 is then
inferred from theoretical mass-radius relations appropriate for white dwarfs.
The parallax method yields a mass estimate of 1.310--1.330 M_sun, for interior
compositions ranging from pure magnesium to pure carbon, respectively, while
the spectroscopic method yields an estimate of 1.318--1.335 M_sun for the same
core compositions. This star is the most massive white dwarf for which a robust
comparison of the two techniques has been made.Comment: 17 pages, including 4 figures, Accepted for Ap.
Precise laser spectroscopy of the antiprotonic helium atom and CPT test on antiproton mass and charge
We have measured twelve transition frequencies of the antiprotonic helium
atom (pbar-He+) with precisions of 0.1--0.2 ppm using a laser spectroscopic
method. The agreement between the experiment and theories was so good that we
can put a limit on the proton-antiproton mass (or charge) difference. The new
limit is expected to be much smaller than the already published value, 60 ppb.Comment: proceeding of the conference, "PANIC02
Quantum Lifetime of Two-Dimensional Holes
The quantum lifetime of two-dimensional holes in a GaAs/AlGaAs double quantum
well is determined via tunneling spectroscopy. At low temperatures the lifetime
is limited by impurity scattering but at higher temperatures hole-hole Coulomb
scattering dominates. Our results are consistent with Fermi liquid theory, at
least up to r_s = 11. At the highest temperatures the measured width of the
hole spectral function becomes comparable to the Fermi energy. A new,
tunneling-spectroscopic, method for determining the in-plane effective mass of
the holes is also demonstrated.Comment: 5 pages, 4 figures. Published versio
Heavy Metal Analysis of Industrial Discharges in Lagos, Nigeria
Waste water samples from three different industrial areas in Lagos state (Ikeja, Apapa and Victoria Island) spanning the dry and wet seasons, were analyzed for Pb, Cu, Cd, Mn and Fe using the atomic absorption spectroscopic method. The mean values of Fe were within the FMEnV and WHO limits used as standard while the mean values of Cd, Cu, Pb and Mn exceeded these limits indicating that these industries constitute source of pollution to the human lives and ecosystem in the areas involved. Utilization of improved method of treatment and frequent awareness to the compliance of the industries were recommended
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