Friday, 28 December 2012

Almost Time

I will soon be embarking on my 3(hopefully) year journey that is my PhD.I can't say I'm not nervous but I must say I'm more excited. I've had quite a long break(almost 7 months) from doing anything really, (bar demonstrating in labs and a bit of reading) so I will have to see how easy it is to get back into the groove of work.

I start Jan 7th quite a strange time but my supervisor has been over in america so I had to wait for him to come back. At least I'm not alone in this I have a fellow PhD student starting with me.


I suppose tell you about the subject of my PhD. I'm going to be observing AGN (Active Galactic Nuclei) using x-rays - what about them has not yet been confirmed still talking to my supervisor about that one.
AGN are thought to be made up of 5-6 regions the first of which is A super massive (billions of times the mass of the sun) black holes which are accreting matter. This liberates the matter of its gravitational potential, as the viral theorem states that it must radiate half of it's energy during it's in fall. Before the matter can accrete on to the central black hole it must lose it's angular momentum. This is done in the second region an accretion disk which forms from in falling matter which is flattened into a disk by it's rotation around the central black hole. The accretion disk emits as a black body with the innermost regions being the hottest and emitting in the extreme ultra-violet. Annoyingly the energy of a photon from the extreme ultra-violet part of the EM spectrum has enough energy to ionise hydrogen, and due to the hydrogen rich nature of our galaxy is completely absorbed.
The third and fifth regions are observed in the spectra of AGN they are the two line emitting regions. The BLR (Broad Line Region) so called as the lines in the spectra are broadened (who said physics is complicated ) the reason for the broadening is thought to be due to it's closer proximity to the black hole. The NLR (Narrow Line Region) is therefore further out than the BLR but it is also less dense as it contains forbidden lines which are emission lines that are normally collisionally suppressed at higher densities (atoms are not allowed to emit there lines normal as they take too long allowing other atoms bump into them) from this knowledge we can limits to the density of the NLR. Both regions are thought to be clumpy with the matter arranged in clouds.
The awake ones of you will have noticed that I missed out the forth region it is known as the dusty torus(ring doughnut shape) which absorbs radiation from the accretion disk and BLR, which heats it causing it to emit in the IR (infra-red). It has the effect of screening the accretion disk and BLR from the observer if it falls in the line of site. This is the basis behind the unified model of AGN, that the difference in AGN types are due to orientation which the AGN is observed from as illustrated in this image.

There is also another distinction between different types of AGN radio loud and radio quite. Radio loud AGN emit much more more in the radio band than their quite counterparts hence the name. This thought to be due to the presence(/or lack of) a relativistic jet.

Hope you have enjoyed my very brief overview the structure of AGN.


P.S. This blog is going to become a place for me to keep track of my day to day work hope you guy's enjoy it, although it's really more for my benefit.

Wednesday, 17 October 2012

Copy attachments from Gmail to Google Drive

I recently made a script that I think could be very useful to people, It works by you attaching the label "Docs"  (which will be created by the script), to a message which you wish to copy the attachments of. Once messages under that label are found the script will copy the attachments over. I also added a feature that makes nested labels(inside "Docs") as folders inside your Google Drive - labels nested inside the nested labels will also be created inside the folder, and so on and so forth. The UI is pretty crude but it gets the Job done. Feel free to give it a try.


Please report and bugs you find.

Sunday, 30 September 2012

A Promise Kept

Ok, so this post is due to a drunken promise with the Rhodes bothers both which apparently read this blog. Thank guys! So anyway in the queue to a local nightclub I said to the brothers that I would summarise my PhD project for them, so here goes.

 The first option for my soon to be project and my favored choice, is to measure the outflow from AGN(Active Galactic Nuclei) and then inferring if the outflow could feed the dusty torus which is used to explain the absence of broad line emitting clouds (sources of emission which a located close to the black hole so are relativistically broadened) this would mean modifying the current unified model of AGN in some way.

The second option which is also quite cool, is to look at AGN which have very luminosity to get a good model for such AGN, to then look at AGN of the same type at higher redshifts (closer to the begining of the universe).

 I would be happy with either project however the first one by far the one which I prefer. Hope the Rhodes brothers enjoy this post. I'm going to bed now! Good night all!

Friday, 11 November 2011

Shakespeare got it!

O God, I could be bounded in a nutshell, and count myself a
king of infinite space

Friday, 7 October 2011

My Dissertation, Decisions Decisions! - X-ray Binaries

Recently I was given the suggested list of topics for my dissertation. However none of them took my fancy, so started my search for another topic. I thought about Active Galactic Nuclei(AGN) as it is the topic for which I would like to study for my Ph.D. Alas it had been done last year and they strongly recommend against something that was done in the previous couple of years.

So I was trying to think of a reasonably exciting topic and hopefully something with some sort of relation to AGN. In my lab work this week we where talking about Binary systems (I've got to update some predictions of when there gonna eclipse) this got me thinking about X-ray Binaries. So I've had a little bit of look around for some paper and books -still in the process of reading them. They're pretty interesting and accretion powered just like AGN which is a win win.

Heres a bit of background on binary star systems their when 2 stars orbit a common centre of mass(around each other) in an X-ray binary system one of the stars is a compact object(neutron star or a black hole). As the compact object has a strong gravitational field is can sometimes take some of the matter from is 'companion' star this produces X-rays hence there name.

So here's what I know so far. X-ray binaries come in two types - when companion star is high or low mass. In the high mass case the companion is massive enough to resist the compact objects gravitational pull however due to its high mass it also burns much hotter and this drives off some matter(this is known as stellar wind), which is then collected by the compact object. These systems tend to undergo pulsations in X-ray observations and there companion star tends to dominate the optical emissions.

The second type is when the low mass companion star can not resist the pull of the compact object. In this situation the matter of the companion closest to the compact object pulled towards it more than the matter on the other side. This creates a distortion and allows some of the matter to pass point at which the companion can pull it back -this is called a Lagrangian point. Once passed the Lagrangian point the matter heads straight for the compact object- This is called Roche-lobe overflow. It can't fall directly in as angular momentum must be conserved so the matter forms a disk around the compact object-this is also true for the former case.

Once in the accretion disk the material loses angular momentum as it does this it gets closer to the compact object before in the inner regions it falls into it. It is from the inner regions of the which the X-rays are emitted.

The energy gained in accretion is gravitational potential energy. Its really just a fancy way of saying the energy given to matter when its pulled on by other matter and as gravity gets stronger the closer the masses. The more massive the object pulling the matter in and the closer the matter gets to the object the more energy is released. So as the compact objects are very very massive the matter falling into them gains a huge amount of energy.

Thats no all I've learned but its getting pretty late and this post has gotten quite long so I'll leave it here for now.

Wednesday, 7 September 2011

Close to 1

In a quantum mechanics lecture last year, the subject of relative values came up. My lecturer said that a certain value was close to 1 then said in this example it was 2. To which one of the other students seemed quite confused and remarked about how he(my lecturer) had just said it was close to 1 to which my lecturer replied 2 is close to 1 it's not like it's a 1,000 or a 1,000,000. A bit of background my lecturer like pretty much all the lecturers at keele is an astronomer so he deals with very large numbers most of the time.

Now it might sound like the student was being very silly but thinking back at it there are an infinite number of values between 1 and 2 but you could say that about any value. I just thought it was interesting to think about the scales of numbers and how to say some value is close to another depends heavily on the context.

Sunday, 4 September 2011

Definition of a Planet

A Planet must...
  • Obit around a Star
  • Be sufficiently large that it's self gravity can overcome rigid body forces (it's nearly round).
  • Have cleared the area around it's orbit from debris

It is the last bullet point that means Pluto is not a planet.