What I'm about...

Today is officially 'Day 2' of this particular Chandra X-ray Observatory data analysis.

Later on, I'll get around to explaining why what I'm doing is worthwhile -- or, at least, why I think it's worthwhile and how I was able to convince a panel of 5-8 people it was worth spending about 6 hours of time on a multibillion-dollar satellite.  For the moment, if you're interested in the science you can check out a previous paper of mine on a similar topic (X-RAY DUST SCATTERING AT SMALL ANGLES: THE COMPLETE HALO AROUND GX13+1).

So, the immediate goal is to extract the scattered light around two X-ray binaries, specifically GX5-1 and GX9+1.  Like most astronomical names, the origin of these come from an obscure source.  All of the 'GX' names come from observations done with an early MIT X-ray sounding rocket - the 'G' stands for 'Galactic' (all these sources are in the Milky Way Galaxy), and the X for 'X-ray'.  The two numbers following are the longitude and latitude of the source, where 0, 0 points to the center of the Milky Way, in the constellation Sagittarius. There's a supermassive black hole there, called 'Sgr A*', that has a mass more than a million times that of our Sun.  But, back to the GX sources.  The important bit about the is that they were seen by a sounding rocket, which could only observe for 5 minutes at time, and an early one at that.  Which means they're bright.  In fact, the GX sources are some of the brightest X-ray sources in the sky.  This is helpful, since it means the scattered light I'm really interested in will also be bright. Of course, there are ways in which it's not so helpful.  We'll get to that.

So far, I've downloaded the latest version of the data from the Chandra archive -- it lists as N004, so the data has been processed 4 separate times by the Chandra team already.  That's mildly unusual, but not shocking.  All it means is that the calibration done by the team has been significantly revised at least 3 times since the data were first taken.  At this point, all of the data are publicly available at the Chandra archive.  If you'd like to play along, the GX5-1 data have the Observation ID 7029, while the GX9+1 data are ObsID 7030 and 7031.  These were both done in 2006.  Normally the Principal Investigator (PI) has 1 year of private access to the data in exchange for being the one who put the initial effort into writing the proposal and suggesting there was something worth doing with it.  I'm the PI for this data, but I got swamped with other projects and didn't have a chance to get to it before the year was up.  Fortunately for me, the data analysis is rather tricky so I doubt anyone else is going to jump on it.

More as work progresses...