<p>I am extracting gamma ray spectrum from Fermi-LAT data. My spectrum is a lot higher than the ones on previous studies of the same object. What could cause a spectrum to go too high?</p>

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2019-07-19T18:43:29.033Z
There are many possibilities: Did the fit work well enough? Is the spectral model the same? Is the object variable? Is only the normalisation higher or is also the index different? Same energy range? To give a useful answer seeing the count map, mode map, residuals as well as fit results would be helpful.
samcarter_is_at_topanswers.xyz
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2019-07-19T18:50:25.590Z
Which calibration version was used? Which time range was analysed?
samcarter_is_at_topanswers.xyz
CC BY-SA 4.0
2019-07-20T01:06:57.993Z
How long were the gamma rays detected?  Longer time, more counts, higher peaks.
Natsfan
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2019-07-20T19:26:06.053Z
@jmh Usually spectra in gamma-ray astronomy are normalised for instrument response and observation time
samcarter_is_at_topanswers.xyz
CC BY-SA 4.0
2019-07-20T21:37:40.493Z
ok. he didn'd mention that so i didn't know it it was raw data or processed in some way. Thanks for pointing that out.
Natsfan
<observational-astronomy><astrophysics><gamma-rays>
Fermi-LAT gamma ray spectrum too high
Edison
# Fermi-LAT gamma ray spectrum too high

(Asked by: username_0 on 2019-07-19)

I am extracting gamma ray spectrum from Fermi-LAT data. My spectrum is a lot higher than the ones on previous studies of the same object. What could cause a spectrum to go too high?

**Tags:** observational-astronomy, astrophysics, gamma-rays

> **Comments:**
> **username_1**: There are many possibilities: Did the fit work well enough? Is the spectral model the same? Is the object variable? Is only the normalisation higher or is also the index different? Same energy range? To give a useful answer seeing the count map, mode map, residuals as well as fit results would be helpful.  
> **username_1**: Which calibration version was used? Which time range was analysed?  
> **username_2**: How long were the gamma rays detected?  Longer time, more counts, higher peaks.  
> **username_1**: @jmh Usually spectra in gamma-ray astronomy are normalised for instrument response and observation time  
> **username_2**: ok. he didn'd mention that so i didn't know it it was raw data or processed in some way. Thanks for pointing that out.  

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## 0 answers

