Feb 10 2011
Steady Sources
The “Fermi Sky Blog” can be reached from the Fermi main web page [1], though I guess it doesn’t hurt to note the direct link here [2].
In the “Fermi LAT weekly report N. 138 … 2011.January.24 – 2011.January.30”, we find the following: “3C 454.3 fairly bright for all the week, with daily flux between 2.5e-6 and 6.4e-6.” This type of report has been a fairly common format in the Fermi Sky Blog, with flux levels often being very low, from sources so far away that it leaves one quite impressed with the technology and analysis methods whatever they may be.
Noteworthy is that “Fluxes are in the unit of photons/cm2/s above 100 MeV. All errors are statistical only.” Gravity is at 313 MeV and, as has been said many times before, the LAT seems designed to measure gravity as one of its main purposes. The designers would not have had to know how gravity works; they would only have had to know the typical frequency range of sources from past data and experience.
Steady sources said to be “fairly bright for all the week” are encouraging to see, because gravity at a given relative location and time period is normally a steady field. Most sources above 100 MeV are indeed steady, and let us be reminded that even the closest celestial body to the earth, the moon, is “an object with an absolutely known gamma-ray output” [3], and a stunning image [4].
[1] http://fermi.gsfc.nasa.gov/
[2] http://fermisky.blogspot.com/
[3] https://www.fruechtetheory.com/blog/2007/11/14/glast-calibration/