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--- main:grb_observing [2014/11/06 01:22]
bruce created
+++ main:grb_observing [2021/01/12 00:50] (current)
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 ====== Observing GRBs ======
+----
+====== Space Backgrounds & Environment======
+----
+===== Particle & CR Environment and Issues =====
+^Document Name+Link^Date^Type^Author^Comment^Keywords^
+|"World Maps of Constant B, L, and Flux Contours", E. G. Stassinopoulos, NASA SP-3054, Goddard Space Flight Center, 1970 {{:main:stassinopoulos_earth_mag_field_particles.pdf|stassinopoulos.pdf}} |1970|NASA Report|Stassinopoulos|Reference on Space Particle Environment|Particle background, latitude, SAA, electron population, particle contours, high background region, map of radiation belts, van allen belts, cutoff of rigidity,COR|
+===== Diffuse X-ray Background =====
+===== Diffuse UV background =====
+ is given in [[Media:1987AJ_____94__876O.pdf]]
+===== Diffuse Optical-IR background =====
+My favorite plot of space (zodiacal) background opt-NIR is the one by Michael Lampton (though I think aldering's analysis below is better:
+{{ :main:lampton_space_bgnd.png?direct&300 |lampton_space_bgnd.png}}
+I believe you can take as definitive Greg Aldering's analysis of space background for SNAP {{:main:aldering01_space_zodi.pdf|aldering01_space_zodi.pdf}} DO NOT USE without attribution!!! (called the "white paper" elsewhere, probably a section of, or a study for the white paper; the original file was just called zodi.ps).
+It is important to understand that the zodi varies depending on angle between sun and pointing.  I *think* in the optical it doesn't vary so much, but don't quote me on that.
+</ul>
+</ul>
 ====== X-ray Observations ======
+----
-[[main:space_backgrounds|Space Backgrounds]] - includes X-ray background
-[[main:xr_band_selection|X-ray Band Selection]] - (how far to integrate up or down).
+===== Spectral Slopes =====
+GRBs You should look at GRB General Observing>Slopes explanation of GRB spectral slopes; I use here BAT-like instrument results. Sakamoto+11 says BAT sees
+low-E PL w/Photon index -1.6 for LGRB.    For SGRB, sakamoto says low-E Photon index -1.2 for SGRB, very different results from Nava
+The DXRB diffuse X-ray Background is complicated and modern papers point out all sorts of curvatures, etc. Me, I'm a lazy bum and use very very old parameterization Zombeck p. 197 , http://ads.harvard.edu/cgi-bin/bbrowse?book=hsaa&page=197, weirdo units are KeV cm^-2/s/Sr/keV
+NA ~ 0.1 keV <E<5 keV (To remind you again: Zombeck parameterization does not cover the soft bump.)
+.5*E^(-.4)      5 keV<E<25 keV
+.*E^(-1.38)  5 keV <E< ~ MeV
+(Better parameterizations have a low-E exponential cutoff and all kinds of curvatures, e.g. I(E) = 7.9 E-0.29 exp[-E/41.1 keV] keV cm-2 s-1 sr-1 keV-1 from ~ 5-30 keV. http://www.slac.stanford.edu/econf/C0307282/lec_notes/kahn/kahn1.pdf)
+===== X-ray Energy Band Selection =====
+Here are my plots and discussions of how this plays out for choosing energy bands for observations. (It is from my script singu!~/projects/ubat/xethresh.pro).
+File:grb_vs_dxrb_spectra.png
+{{ :main:observing_xbands:grb_vs_dxrb_spectra.png?direct&600 |}}
+So, the DXRB is almost as hard as SGRB up to ~ 25 keV, then it is very steep.
+Now let's see that in Counts space, which helps visualize results below.
+File:grbvdxrb_counts.png
+{{ :main:observing_xbands:grbvdxrb_counts.png?direct&600 |}}
+How far should I integrate up or down?
+==== How Far to Integrate Down in Energy ====
+==== How far to integrate up in energy  ====
+X-rays-Observing>Energy Band Selection
+The DXRB has a "thermal-ish" bump that dominates from tenths of keV to ~ 3-5 keV. For this reason, you don't want to go below 5 keV, so 5 keV is the obvious lower bound of energy. What do you gain by going to high energy?
+If you integrate spectra in count rate space, you see that LGRB rise briskly to ~ 25 keV, then gradually flatten. File:intgd_spectra.png
+{{ :main:observing_xbands:intgd_spectra.png?direct&600 |}}
+However, if you make a VERY SIMPLE assumption that the background is dominated by the DXRB (it isn't!! There are particles!!!!) you could make a simple argument that you should integrate to high energies because S/N keeps improving:  File:simplified_snr_vs_Emax.png
+{{ :main:observing_xbands:simplified_snr_vs_emax.png?direct&600 |}}
+So, I suspect the particle background spectrum is very hard, and truth is not so optimistic (without active veto). Still, it seems that it should be OK to go all the way up to 100 keV (but recall Chris' caution about being saturated by particle and other events just over your maximum energy threshold; take care with finite resolution and dynamic range).
+Note that the SGRB are still rising at the highest energy while the LGRB is flattening.
+----
+===== What about integrating down? =====
+How far down should one go in energy before this is not favorable increase in S/N?
+{{ :main:observing_xbands:grb_intgd_down.png?direct&600 |}}  this from singu!~/projects/xethreshhi2lo.pro
+{{ :main:observing_xbands:grb_snr_intgd_down.png?direct&600 |}}
+So, its quite clear that you still get photons for BOTH spectra in this idealized picture.  I think even HETE got like one SGRB (don't quote me).
 ====== Optical Observations ======
+----
+===== Lya Forest Spectroscopy =====
+Of interest because high-z grb may provide very bright light sources for very high-z Lyman Alpha Forests.
+Some papers to check out some day:
+http://arxiv.org/abs/1309.1477v1      Observational Requirements for Lyman-alpha Forest Tomographic Mapping of Large-Scale Structure at z ~ 2

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