3,000 research outputs found
RFI Identification and Mitigation Using Simultaneous Dual Station Observations
RFI mitigation is a critically important issue in radio astronomy using
existing instruments as well as in the development of next-generation radio
telescopes, such as the Square Kilometer Array (SKA). Most designs for the SKA
involve multiple stations with spacings of up to a few thousands of kilometers
and thus can exploit the drastically different RFI environments at different
stations. As demonstrator observations and analysis for SKA-like instruments,
and to develop RFI mitigation schemes that will be useful in the near term, we
recently conducted simultaneous observations with Arecibo Observatory and the
Green Bank Telescope (GBT). The observations were aimed at diagnosing RFI and
using the mostly uncorrelated RFI between the two sites to excise RFI from
several generic kinds of measurements such as giant pulses from Crab-like
pulsars and weak HI emission from galaxies in bands heavily contaminated by
RFI. This paper presents observations, analysis, and RFI identification and
excision procedures that are effective for both time series and spectroscopy
applications using multi-station data.Comment: 12 pages, 9 figures (4 in ps and 5 in jpg formats), Accepted for
publication in Radio Scienc
Nature of cyclical changes in the timing residuals from the pulsar B1642-03
We report an analysis of timing data for the pulsar B1642-03 (J1645-0317)
gathered over the 40-year time span between 1969 and 2008. During this
interval, the pulsar experienced eight glitch-like events with a fractional
increase in the rotation frequency Deltanu/nu=(0.9-2.6)x10^{-9}. We have
revealed two important relations in the properties of these peculiar glitches.
The first result shows that there is a strong linear correlation between the
amplitude of the glitch and the time interval to the next glitch. The second
result shows that the amplitude of the glitches is modulated by a periodic
large-scale sawtooth-like function. As a result of this modulation, the glitch
amplitude varies discretely from glitch to glitch with a step of 1.5x10^{-9} Hz
in the range (2.4-6.9)x10^{-9} Hz. The post-glitch time interval also varies
discretely with a step of about 600 days in the range 900-2700 days. An
analysis of the data showed that three modulation schemes with modulation
periods of 43 years, 53 years and 60 years are possible. The best model is the
60-year modulation scheme including 12 glitches. We make a conclusion that the
nature of the observed cyclical changes in the timing residuals from PSR
B1642-03 is a continuous generation of peculiar glitches whose amplitudes are
modulated by a periodic large-scale sawtooth-like function. As the modulation
function is periodical, the picture of cyclical timing residuals will be
exactly repeated in each modulation period or every 60 years.Comment: 26 pages, 9 figures. Accepted for publication in the Astrophysical
Journa
An Analysis of Potential Tax Incentives to Increase Charitable Giving in Puerto Rico
Compares options for improving tax incentives for charitable giving, including lifting the ceiling on deductions as a percentage of adjusted gross income, and estimated effects on nonprofits in Puerto Rico, where average giving is high relative to AGI
Developing a data relay network for monitoring hydrologic conditions in south and central Florida
There are no author-identified significant results in this report
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