Pulsars and the Ooty Radio Telescope

Well, there's enough content about Quasars on my blog. It's about time i talked about Pulsars - though they sound similar, they are in no way related to one another! Simply put, Pulsars are a Galactic phenomenon i.e they are found in the Milky way galaxy and Quasars are an Extra-Galactic phenomenon i.e they are found in galaxies outside out own galaxy - the Milky way galaxy! 

And, pardon the technical jargon, Pulsars are rapidly spinning neutron stars which emit radiation from their polar regions. And since their spin axis is different from their magnetic axis, the radiation is perceived/observed only when the magnetic axis is aligned to our line of sight! 

Basically, a Pulsar is like a light house. Light is only observed periodically and if you're not standing right in the place - you might not be able to observe it! In the case of the Pulsar, the cone of light is much smaller and the period of the pulses is very small - of the other of milli seconds. 

I was recently part of a Pulsar Observatory for Students program, at the Radio Astronomy Center, Ooty, NCRA-TIFR. During the program, we were taught how the pulsars work, how to observe pulsars and so on. After a couple of days of theory, we were asked to choose a Pulsar from a list of 10, which we would them observe and study! We could either blindly choose a Pulsar or be serious, look at the properties of the 10 pulsars and choose the *best* pulsar, so to speak! So, here's the list of Pulsars we were asked to choose from. 

The Pulsars are named as follows - B0031$-$07 refers to a pulsar observed at an RA of $00hr 31min$ & Dec of -07$^\circ$ and the B refers to the fact that the B1950 epoch positions are used! 

Now, if you're interested or bored, look at the properties of these pulsars and determine which of these you think is the best. To start off, here are some places where you can look for the properties of the Pulsar - ATNF Pulsar Catalogue, NED. And you should rate the Pulsar on it's period, the derivative of the period - which determines the rate at which the Pulsar is slowing down, the dispersion measure - which is a measure of the electron density in the line of sight towards the Pulsar and last but not the least, strength or Intensity of the Pulsar! 
  •  B0031$-$07  --- 00h:31m:36.37s  --- $-$07$^\circ$:38$'$:25.30$"$ 
  •  B0148$-$06  --- 01h:48m:52.61s  --- $-$06$^\circ$:49$'$:51.70$"$ 
  •  B0329$+$54 --- 03h:29m:11.02s  --- $+$54$^\circ$:24$'$:36.93$"$ 
  •  B0628$-$28  --- 06h:28m:51.83s  --- $-$28$^\circ$:32$'$:33.46$"$ 
  •  B0740$-$28  --- 07h:40m:47.81s  --- $-$28$^\circ$:15$'$:33.36$"$ 
  •  B0818$-$13  --- 08h:18m:06.03s  --- $-$13$^\circ$:41$'$:23.04$"$ 
  •  B0833$-$45  --- 08h:33m:39.27s  --- $-$45$^\circ$:00$'$:10.20$"$ 
  •  B0950$+$08 --- 09h:50m:30.54s  --- $+$08$^\circ$:09$'$:45.05$"$ 
  •  B1133$+$16 --- 11h:33m:27.43s  --- $+$16$^\circ$:07$'$:36.77$"$ 
  •  B1237$+$25 --- 12h:37m:11.92s  --- $+$25$^\circ$:10$'$:17.30$"$ 
  •  B1642$-$03  --- 16h:42m:24.69s  --- $-$03$^\circ$:12$'$:30.93$"$ 
  •  B1749$-$28  --- 17h:49m:49.27s  --- $-$28$^\circ$:06$'$:00.70$"$ 
  •  B1857$-$26  --- 18h:57m:42.26s  --- $-$26$^\circ$:04$'$:59.30$"$ 
  •  B1929$+$10 --- 19h:29m:52.04s  --- $+$10$^\circ$:53$'$:04.28$"$ 
  •  B1937$+$21 --- 19h:37m:28.74s  --- $+$21$^\circ$:28$'$:01.35$"$ 
  •  B2016$+$28 --- 20h:16m:0.18s   --- $+$28$^\circ$:30$'$:30.11$"$ 
  •  B2045$-$16  --- 20h:45m: 47.07s --- $-$16$^\circ$:27$'$:52.34$"$ 
For example, I chose the Pulsar B1749$-$28. And if you look at it's properties in ATNF Pulsar Catalogue, the NED database and the Vizier page - you can notice three interesting things.


  • The period of the pulsar is approximately 0.562s. 
  • The strength of the Pulsar is roughly 2000mJy at the ORT (Ooty Radio Telescope) observing frequency of 326.5 MHz
  • The dispersion measure is 50.88 $pc/cm^-3$ - as i mentioned, is a measure of the electron density along the line of sight!
  • The Pulsar lies towards the galactic center and hence the background of the Pulsar is extremely large! 
These are some of the reasons why i chose this Pulsar!
If you're interested and if you have the time, you should look up the properties of these pulsars as well. Tell me which you think is the *best* Pulsar and why! 

PS - I mentioned that the strength of the Pulsar B1749$-$28 that i chose is ~2000 mJy at 326.5 MHz - which is the observing frequency of the ORT. But in the links i provided, only the strengths of the Pulsar at 400, 600 and 1400 MHz are mentioned! I back calculated what the strength of the Pulsar should be at 326.5 MHz using the fact that the Strength of the pulsar is a power law i.e $$S_{\nu} = \nu^{-\alpha}$$ where $\alpha$ is in the range -1.6$\pm$0.3. Refer to arXiv:1302.2053 for more information. Also, you can go through my presentation for more information on Pulsars and my work as part of the POS program.

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