Tempo can't print DM vs time list

[Former user]

I wanna plot a figure of orbital vs DM(like figure 1).I use tempo2,click DM and re-fit,and my x-axis is orbital phase. And then I click 'list' and it showed like figure 2.I stiil can't get the information about phase and DM. How I use tempo2 then I can get figure 1?

Thank you so much!

[Michael Keith]

Hello - are you trying to fit DM as a function of orbital phase? You probably need to fit for DM in small windows of orbital phase or something. This is not super easy - likely the best way is to split your tim file into obital phase bins. You could get a handle on this by printing the orbital phase using e.g. the general2 plugin, e.g.

tempo2 -output general2 -f my.par my.tim -s “{sat} {binphase}\n”

And then chop up your tim file appropriately and fit for DM on each small tim file.

Alternatively if you are confident with C/C++ you could fairly easily write a plugin to do it I think.

[Diem Carpe]

Thank you so much! Another questions is tempo2 can fit DM as a function of time or date(MJD)?Is tempo2 can print a list, including one column is time(or MJD date?),one column is DM measure?

[Michael Keith]

Fitting for DM as a function of time is not a ‘trivial’ exercise and the method you want to use will depend on what kind of data you have. E.g. do you have multiple frequencies at every observation epoch or are things more irregular? How many frequency bands do you have? Does the pulsar have significant noise in addition to the DM variations?