Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.naic.edu/~astro/School/Talks/handson_gbt1.pdf Дата изменения: Mon Jul 18 17:57:58 2005 Дата индексирования: Sat Dec 22 10:45:13 2007 Кодировка: Поисковые слова: http www.badastronomy.com bad tv foxapollo.html

Search for a 2nd Double Pulsar Binary
Steve Begin, Marta Burgay, Julia Deneva, James Sheckard Project Leader : Scott Ransom


Background Info
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Pulsar J1906+07, discovered in Sept. 2004 by P-ALFA P=144ms, DM=217.77 Characteristic age ~10^5 yr Porb = 3.98 hours Periastron advance ~ 7.777 deg/yr Mtot ~ 2.7 Msun

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Mpulsar < 1.7Msun Mcompanion > 0.9 Msun


Companion Type?
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Lower mass limit for companion: 0.9 Msun-high Could be a Neutron star If it is, it must be older than J1906+07 It would have had time to accrete and speed up during the giant phase of J1906+07 Very compact system. Asini ~ Rsun/2 Potential companion with P ~ tens of ms


Scientific Incentive
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Measure of relativistic effect

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Shapiro delay Periastron advance

Eclipse (probe of magnetosphere) Mass ratio!!! (free post-Keplerian parameter)


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Observation
What went wrong:

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Spigot raid disk were down The GBT dish and spectrometer ignored us Astrid was capricious Total setup time ~ 2 hrs Scott and Karen were there... We got some data!!!

What went right

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1.25 hrs in S-Band


Acceleration Search
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Dedisperse (known DM of J1906+07) Apparent period Doppler-distorted Assume constant acceleration over observation time Stretch/compress time series for list of trial acceleration parameters For trial parameter close to true acceleration--period constant in adjusted time series FFT & harmonic sum


Variant on the Theme
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Assuming orbital parameters, we can correct for binary motion completely Parameters constrained by observations of the known pulsar

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Restricted our A*sin I values between 1.0 -2.0 lightseconds This corresponds to a mass range of 1.1 to 1.6 Msun for the companion




Dynamic Power Spectrum
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No acceleration correction Divide observation in shorter segment Calculate the power spectrum for each segment Stack them on top of each other Create a 2-D array of time interval vs. frequency Binary Pulsar should show up as a curve in this plane



Brand New Ter5 found with DPS Porbital = 4.1 hours, Mcompanion ~ 20 Mjupiter


Results
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We rediscovered J1906+07 by both acceleration searches and dynamic power spectrum No indication of a companion pulsar beamed in our direction We learned quite a bit