Useful stuff 2
This is a list of stuff (the kind of stuff that gets tossed onto myriad post-it notes or scribbled on my hand and eventually lost. Context may need inferring. Using MathJax to render equations, so enable Javascript.
Conversions
- Gyroradii of relativistic prtl: 1 PeV in 1 μG is 1 pc; 1 GeV in 1 μG is 0.2 AU = 3e12 cm.
- 1 km/s = 1 pc/Myr
- \(10^4\) K gas has sound speed \( c_\mathrm{s} \sim 10\) km/s
Tools
- Galactic NH calculator - see page/links for doc. Computes \(N_{H_{\mathrm{tot}}} = N_{\mathrm{HI}} + 2 N_{\mathrm{H}_2}\) from Leiden-Argentine-Bonn HI and COBE/DIRBE & IRAS/ISSA dust maps.
- WebPIMMS to convert between mission count rates and fluxes.
- Flux converter (flux, magnitude, etc...)
- Zombeck's Handbook of Space Astronomy & Astrophysics, 2nd ed.
- ISM
Catalogs and things
- Chandra SNRs
- Dave Green's SNR catalog
- Ferrand / Safi-Harb, census of high energy SNR observations
- Rybicki/Lightman...
- N{x} for Magellanic Cloud (MC) objects indicates Henize (1956ApJS....2..315H); SIMBAD advises use of "LHA 120-N {identifier}".
- DEM {L/S}, for {L/S}MC objects, indicates Davies, Elliott, Meaburn (1976MmRAS..81...89D).
Some Galactic SNRs (excluding PWNe)
- Tycho - G120.01+1.4 (3C10, SN 1572)
- Kepler - G4.5+6.8 (3C358, SN 1604)
- Cas A - G111.7-2.1 (3C461)
- RCW 86 - G315.4-2.3 (?SN 185?)
- ? - G1.9+0.3 (youngest galactic SNR)
- SN 1006 - G327.6+14.6
- Vela Jr. - G226.2-1.2
- ? - G347.3-0.5 (RX J1713.7-3946, ?SN 393?)
Notable soft X-ray lines above 1 keV-ish
Some of my notes on soft X-ray lines relevant to SNRs, link and a nice write-up with plots of several SNe (Cas A, 0102-72.3 in SMC, Kepler, 1987A) by J. Kolena.
More thorough catalogs: Bearden catalog of X-ray lines/energies (1967, Rev. Mod. Phys.) and AtomDB. List of K and L-shell lines, for non-ionized atoms (link, link 2 [pdf]).
- 1.34 keV, Mg He \(\alpha\)
- 1.85 keV, Si He \(\alpha\)
- 2.18 keV, Si He \(\beta\)
- 2.45 keV, S He \(\alpha\)
- 2.89 keV, S He \(\beta\)
- 3.12 keV, Ar He \(\alpha\)
- 3.88 keV, Ca He \(\alpha\)
- 6.8 keV, Fe He/Ly \(\alpha\)
Synchrotron radiation, constants and stuff
Equations in CGS (see Pacholczyk, 1970 and NRAO ERA)
Diffusion (Bohm), \(C_D = c/3e = 2.083 \times 10^{19}\)
From \(\left\langle dE/dt \right\rangle = bB^2E^2\) we have \[ \tau_{\mathrm{synch}} = \frac{1}{bB^2E} . \] Here, \[ b = \frac{2}{3} \cdot \frac{2 e^4}{3 m^4 c^7} = 1.57 \times 10^{-3} . \] Left factor \(2/3\) arises from \(\sin^2\vartheta\) (average over solid angle), right factor is Pacholczyk's "\(c_2\)". See Pacholczyk (3.32), Condon/Ransom (5B9, 5B10).
Critical frequency: \[ c_1 = \frac{3e}{4\pi m^3 c^5} = 6.27 \times 10^{18} \] Used for \(y = \nu / (c_1 E^2 B)\), scaled electron emissivity freq.
Peak frequency: \(\nu_m = c_m E^2 B\), where \(c_m = 1.82 \times 10^{18}\)
\[
\mathrm{E}(\nu_m) = (22.8\;\mathrm{TeV})
\left(\frac{h\nu_m}{1\;\mathrm{keV}}\right)^{1/2}
\left(\frac{B}{100\;\mathrm{\mu G}}\right)^{-1/2}
\]
Note that \(c_m \approx 0.29 c_1\). Critical frequency for the \(\delta\)-approx. (?)
Here \(c_m\) corresponds to peak radiated power.
Gyrofrequency of an electron: \[ \nu_{\mathrm{G}} = \frac{eB}{2\pi m c} \] Critical frequency (Condon/Ransom (5C2)) \[ \nu_c = \frac{3}{2} \gamma^2 \sin\alpha \;\nu_{\mathrm{G}} = \left(\frac{3}{2} \sin\alpha \frac{e}{2\pi m^3 c^5}\right) E^2 B \]
Useful numbers
Preferably those that don't already show up on standard cheat sheets (Planck's constant and what have you).
20 cm3 sphere = 3.37 cm diameter
60 cm3 sphere = 4.86 cm diameter
Useful snippets
Perl one-liner to filter-and-print: perl -lne 'print "$1" if /^(\d{5})/;' file.txt
.
Here -l does nice newline handling (chomp input, make print act like
say). -n is similar to -p (wraps command in while(⟨⟩)
loop) but doesn't have the continue print block (-p could be more
succinct if we weren't filtering).
Finally, -e is just executes the code string...
This particular example extracts obsids (5-digit numbers) from all strings prefixed with obsids in the file.
Trim trailing whitespace in Vim: %s/\s\+$//gc
.
I.e., + must be escaped but $ is not (which I often forget).
Other vim whitespace troubleshooting:
- get ascii/unicode value of char under cursor: ':ascii'
- yank and search using default register: 'v', 'y', '/', 'Ctrl-R 0'
- search hex: '/\%x{hexcode}'
- space: 0x20
- non-breaking space: 0xa0
Add new word to Vim spellfile: 'zg'; undo with 'zug'.
Plotting unfolded spectra in XSPEC is dangerous. One workaround: set model to unity by freezing powerlaw with normalization 1 and slope 0. Then the plotted data are simply data / response. Source: slides by M. Nowak, and trick in turn by S. Vaughan.
Local pip install: pip install --user [package]
, pushed to
~/.local/[...]
. Add ~/.local/bin/
to
$PATH
if needed.
ipynb users: nbstripout. Using git filter (clean/smudge) helps with diffs. TODO: twiddle hooks to preserve outputs in your working copy?
https://github.com/trimstray/the-book-of-secret-knowledge
Vim search and replace in ALL buffers (from Vim Tips wiki): :bufdo %s/pattern/replace/gc
UNIX find command: find . -name fname
GDB cheatsheet:
- break (frame):(line #)
- run
- info locals
- whatis
- p (var)
- select-frame
- set var {-}={-}
- next
- continue
- step