[radioastro] Re: Pulsar signal to noise ratio in Radio JOVE, Pulsar nulling in PSR B1112+50

  • From: Victor Herrero <hubbleed@xxxxxxxxx>
  • To: Juan Fernando Tonatiuh Hernández Escobar <cecilixz@xxxxxxxxxxx>, Marco Nicolini <heygio@xxxxxxxx>, Peter Hughes <PHughes@xxxxxxxxxx>, David Fields <fieldsde@xxxxxxx>, Steve McCauley <esmac@xxxxxxxxxx>, Dave Typinski <davetyp@xxxxxxxxxx>, "Whitham D. Reeve" <whitreeve@xxxxxxxxx>, Terrence Flower <tfflower@xxxxxxxxxx>
  • Date: Tue, 17 Aug 2010 09:34:33 -0700

Hello Everybody,

David, thank you for your comments.

The signal to noise ratio with a Radio JOVE Kit is very low.
Let us estimate it:

Signal/Noise ~
FluxDensity*Area*sqrt(2*Bandwidth*IntegrationTime*DutyCycle)/(Boltzman*Tsystem)

If:
Signal/Noise > 3
Area = 150 meter^2
Bandwidth = 1E4 Hz
IntegrationTime = 3600 second
DutyCycle = 0.1
Boltzman = 1.4E-23  watt per kelvin per hertz
Tsystem = 5E4 kelvin

Then: Flux density must be > 520 Jansky (1E-26 watt per meter^2 per Hz)

Studying the ATNF pulsar catalog;
http://www.atnf.csiro.au/research/pulsar/psrcat/
and extrapolating to 100 MHz, I do not find any candidates near 520 Jansky.

Pulsar flux densities peak around 100 MHz, see Malofeev et al. 1994:
http://adsabs.harvard.edu/abs/1994A%26A...285..201M

Kuzmin and Losovsky 2001:
http://adsabs.harvard.edu/abs/2001A%26A...368..230K
report flux densities for millisecond pulsars, measured near 100 MHz.

The strongest ones reach up to 0.48 Jansky, with spectral indices near -2. I
expect their extrapolated 20 MHz fluxes will be well under 520 Jansky,
assuming no turn-over.

An impractical 100 hours of integration time will produce only a 10 fold
improvement in S/N.
Millisecond pulsars will be very difficult to observe with Sky Pipe software
and Kit hardware.

Please confirm the estimate, and continue discussing your interesting
comments about pulse nulling mechanisms.

I look forward to discovering a way to observe pulsars with RJ Kits.

I pictured the lovely moon/star sculpture in Big Sky Montana, in July 2008
during my summer vacation from Tucson Arizona.

Best regards,

Victor

------------------------------------------
Victor,
Many thanks for your email. What was the reason, do you think, that your
group's signal record did not show pulsar emission using Jim Prooyen's
software.

I was already enjoying the lectures on the astron.nl site. I wonder if
pulsar nulling might be due to tumbling, as would occur with an unstable
top. Perhaps classical mechanics (classical theoretical physics) would show
constants of motion of top tumbling, that could be tested against the
periodic pulsar nulling shown in the data on this site. This is of course
purely speculation.

Your LOFAR page on your website was also a pleasure to visit. What is the
origin of the nice little rustic moon/star sculpture at the end of the page?

Cheers,
David Fields
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