Today I will be previewing a neat result me and Tom have been working on for the past few months. It’s going to be a bit more technical than my usual post, so please bear with me.
In September 2017, a new black hole X-ray binary called Maxi J1535-571 was discovered, and Tom started observing it with ATCA, an Australian radio telescope. At the same time, many of our collaborators also looked at the source with infrared, optical and X-ray observatories, producing lots of really interesting data to analyze. This is really useful because while X-ray and optical data gives us some information about the material falling towards the black hole, radio and infrared data tells us about the jet. By combining all this data, we can try to understand how the jet and accreting material are connected to each other.
After gathering the data, my role was to use theoretical models to understand which conditions in the plasma are leading to the emission we observed. The result is a very busy plot that looks like this:
This is pretty technical so let me walk you through it. For starters, ignore the bottom part of the plot and only look at the top panel. All the colored dots are the data we gathered. The X axis is the frequency at which we observed the source, the Y axis is how luminous the source was – so a point at the top left means low frequency emission is bright, one at the bottom right means high frequency emission is faint, and so on. The important thing here is to remember the last paragraph – the jet emits at low and intermediate frequency, on the left hand side of the plot; the accreting material at high frequency, on the right hand side.
The different colors indicate different days in which we observed, and the straight line shows the theoretical model we used to explain the data for each day. What you can note quite easy is that the right hand side remains relatively steady, with just a fairly small increase, while the left hand side changes a lot. This means that the accreting material is not changing all too much, but the jet is, especially between September 16th (black line) and 17th (blue line)!
The next step was to understand how much the jet emission was changing. This is where our theoretical model helped – with some simple math that I’ll spare you, I figured out that the time over which the jet emission is expected to change should be about 5 minutes. Doing more in-depth analysis, we found that indeed, the low frequency radio luminosity was fading over those times – the jet was disappearing without the in-falling gas really caring much!
This is interesting because it’s contrary to what I said initially – that we expect the in-falling and out-falling material to react to and interact with each other. Here, the jet goes away, and the in-falling plasma doesn’t care all that much. We’re still not sure why or how jets are related to the accreting gas, but this gives us a hint that if we are to understand that connection, we’re going to need to be very clever with your observations, as 5 minutes could make all the difference between catching a jet that’s nice and bright, and one that’s fading and going away!
