Excitement, despair, and how to tell the difference

EDIT: This post was mostly written a week ago on the train down to London. I’ll try to catch up with everything in the meantime as soon as I can.

FYI: This is likely to the be the first in a number of posts as I try to catch you up with my hectic life over the last few weeks.
Since my last post about the meeting in Oxford, there’s been a huge amount of activity and emotion (chiefly excitement and despair, in approximately equal measure). You may recall my post a few weeks ago about the mysterious fast transient we serendipitously discovered with the pt5m. I’d decided it wasn’t moving, and that the intrinsic colour of the flash was quite blue, so our favourite theory back then was that it was a very bright stellar flare from a dim M-dwarf star. The problem was, we couldn’t identify a quiescent counterpart in any available catalogue (see image below), meaning that if this was an M-dwarf flare, the star itself must be very faint, and the amplitude of the flare must have been enormous. We could set a minimum flare amplitude of 6-7 magnitudes, which means an increase in brightness of 1000 times the normal level, at least. This is a rather rare occurrence, and so would be very interesting in itself.

This screenshot shows the position of our transient source (purple cross) with a wide gap around it. There are no sources in *any* astronomical catalogue at any wavelength at this position

This screenshot shows the position of our transient source (purple cross) with a wide gap around it. There are no sources in any astronomical catalogue in any wavelength at this position.

The big news on the day after the Oxford meeting was that whilst looking over the images of the same field from the weekend, I spotted another fast transient event! Even more incredible though, was that this one was clearly a diffuse source, showing a kind of dumbbell shape, like two sources, just touching, fading in unison (later we noticed a third little blob right next to the others, also fading at the same rate, thus presumably of the same origin). This new event was not quite as bright as the previous one, and some 13 days later, but was very nearly in the same place in the sky (about 15 arcseconds away). This was wonderfully exciting, and had both my supervisors grinning and celebrating with a trip out to get “posh coffee”. I use this situation to define ‘excitement’.
These two events could of course have been completely coincidental and unrelated, but after ruling out all the “dull” explanations (reflective glints from satellites, comets and ghosts in the telescope optics) we came up with a plausible (though unlikely) explanation. We proposed that the original flash was indeed a very bright stellar flare from an incredibly faint dwarf or young star, perhaps shrouded in clouds of gas and dust some 300 light years away. The second, diffuse flare could then be a reflection of the original flash by a surrounding gas cloud, at a distance of 13 light days (about 10 times the size of Pluto’s orbit). This was a very interesting idea, and one that could hopefully be proved by the discovery of the faint quiescent source.
Both Vik and Stu set about contacting their buddies at big telescopes (Stu had a friend working at the UK Infra-Red Telescope in Hawaii – infra-red observations are useful for probing through thick gas or dust clouds, and Vik had a number of contacts at the Gran Telescopio Canarias on La Palma – the biggest telescope in the world!), and both managed to persuade the top dogs of each telescope to take some deep images to try to find a background source. By lunchtime on Monday, just 6 months into my PhD, I had my hands on data from the world’s biggest telescope. This was amazing, but does highlight the still prominent issues with modern astronomy; if you’re close to the right people, you have a much better chance at finding a back-door route to otherwise very competitive telescope time. Anyway, that’s an entire discussion in itself, which I won’t go in to now.

After spending almost an entire day fighting with IRAF (astronomy’s most widely used yet still very user-unfriendly software), I was able to combine the GTC images (which gave a limiting g-band magnitude of 28 – astro geeks will appreciate that this is outrageously deep) to find… well, nothing. Apparently the UKIRT images showed nothing either. At this point my hourly use of the word “mystery” began an exponential increase, and my supervisors and I were thoroughly stumped.

When I came into the office the following day, I had a strange urge to re-check the original data for movement, just in case I’d missed something. It turns out I had, and that day soon developed without question into the worst day of the PhD so far. I hadn’t watched closely enough when I was checking if the original transient was moving with respect to the other stars in the field. It was a very subtle, minor movement, but it was definitely present when studied very closely. This was a terrible mistake to have made. Something moving, even as slowly as this was, could not be at a cosmological or even galactic distance. It must be relatively nearby (within half a light year, I later calculated), and thus probably much, much less interesting. With this single mistake, I’d managed to waste well over a week of both my supervisors’ time, my own time, and about 3 hours of observations on the biggest telescope in the world (this costs around 10,000€ a night, so let’s say I wasted over 2,000€). To say I was annoyed at myself would be the understatement of the year. I was devastated, angry at myself, and felt like the biggest idiot ever to be invited to undertake a PhD in science. The look of disappointment on my supervisor’s face when I told him crippled any sense of purpose I had left, and I went home mentally drafting a letter of resignation. I use this situation to define ‘despair’.

After pep talks from my lovely housemates, I did come back in to the office for the rest of the week, and tried to focus on other projects as best I could. Despite trying hard to avoid my supervisors, we still ended up discussing what this event could actually be. The leading theory for a couple of days, proposed by Vik, was that the flash was simply the glint of a slowly rotating satellite, perhaps in a geosynchronous orbit (where it stays above the same spot on the surface of the Earth at all times). After sitting and thinking about it for long enough, I had a revelation: this object couldn’t be a satellite. In fact, it couldn’t be anything orbiting Earth. Though it was moving too quickly to be anything further away than the nearest star, it was moving too slowly to be in an orbit around the Earth (it would have a distance of 5 million km – that’s 13 times the distance to the moon!). Sadly, this epiphany occurred late on Thursday evening, when most people had left the office, and both my supervisors had gone home to pack for the upcoming trip to Thailand, so I had no-one to celebrate/ponder with. This couldn’t be a satellite (nor could it be an asteroid, as the fading brightness was too fast) and must be something at least mildly interesting, or some bizarre technical glitch (and therefore still something useful for other people to know about). This was enough to lift my spirits, and felt like a relief. Partly because what we’d discovered was still of interest and could perhaps form a chapter in my thesis, but mostly because I’d managed to disprove my supervisor’s satellite theory (with a little help from office-mate Chris). I felt less of an idiot, though no less confused about what to do. On a related note, an interesting article was recently published discussing ‘Imposter Syndrome‘, which is relevant here I think. The mystery remains unsolved, but the experience will hopefully prove useful to others working in transient astronomy, so there’s a chance it will still be publishable. More on this later, I imagine.

After a roller-coaster month of October, it was time to head out to Thailand for 6 weeks to commission ULTRASPEC and support the local astronomers in its use. I hope the next post will be shorter and sooner, but right now we’re heading to bed – it’s 4am and the weather has been terrible all night. Goodnight!


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