Abigail Hedden

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The advent of large format (~100 pixels) spectroscopic imaging cameras at submillimeter wavelengths would fundamentally change the way in which astronomy is performed in this important wavelength regime. While the possibility of such instruments has been discussed for more than two decades, only recently have advances in mixer technology, device(More)
We have used the Arecibo telescope to measure the H i absorption spectra of eight pulsars. We show how kinematic distance measurements depend on the values of the Galactic constants R0 and 0, and we select our preferred current values from the literature. We then derive kinematic distances for the low-latitude pulsars in our sample and electron densities(More)
A spectral-line survey of IRC+10216 in the 345 GHz band has been undertaken with the Submillimeter Array. Although not yet completed, it has already yielded a fairly large sample of narrow molecular emission lines with line-widths indicating expansion velocities of ∼4 km s, less than 3 times the well-known value of the terminal expansion velocity (14.5 km(More)
This REU summer project dealt mainly with analyzing data and determining the periods of certain types of pulsating variable stars called RR Lyraes and Cepheids. Pulsating variables periodically change in brightness over a certain amount of time for reasons having to do with the internal structure of the star itself. Dr. Horace Smith has been studying such(More)
We have searched for OH absorption against seven pulsars using the Arecibo telescope. In both OH mainlines (at 1665 and 1667 MHz), deep and narrow absorption features were detected toward PSR B1849+00. In addition, we have detected several absorption and emission features against B33.6+0.1, a nearby supernova remnant (SNR). The most interesting result of(More)
We have constructed an 810 GHz receiver system incorporating a HIFI Band-3 superconductor-insulatorsuperconductor (SIS) mixer developed for Herschel space observatory and a wide-band SiGe low noise amplifier (LNA) designed at Caltech. The instrument is currently installed at the RLT telescope (elevation 5500 m) in northern Chile. Hot/cold (280K/72K) load(More)
Fast load impedance tuning of a varactor diode matching network to maximize amplifier gain in realtime reconfigurable circuitry is demonstrated. A published tunable varactor-diode matching topology is designed for operation at 1.3 GHz to provide significant Smith Chart coverage. A steepest-ascent algorithm is applied for fast optimization, and measurement(More)
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