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I have a paper out today with @jotajotahermes and Boris Gaensicke! A fanTESStic little result about my favourite white dwarf: https://arxiv.org/abs/2006.10806 ">https://arxiv.org/abs/2006.... 1/7
GD394 is a hot white dwarf with a lot going on, that I spent much of my PhD and quite a long paper failing to explain. For the story so far, see this talk I did for @AoTATX https://www.youtube.com/watch?v=Vvpvck0x20c">https://www.youtube.com/watch...
or this thread about my first Gd394 paper 2/7 https://twitter.com/astrodave2/status/1067817979369406465">https://twitter.com/astrodave...
or this thread about my first Gd394 paper 2/7 https://twitter.com/astrodave2/status/1067817979369406465">https://twitter.com/astrodave...
So key point: GD 394 was varying a lot in extreme ultraviolet (EUV) light, but my follow up with Hubble didn& #39;t see any variation. But looking with the TESS spacecraft, we can see that it& #39;s juuuuusssst about varying in optical light, with the same period as the EUV! 3/7
The difference in amplitude is huge - ~25% variation in the EUV, 0.1 % in TESS. So is it the same thing? Hard to tell. Looking at the two light curves, the TESS light curve doesn& #39;t really look like the EUV one. But the signal to noise ratio of the TESS data is low... 4/7
...so it& #39;s hard to tell if the same spot model that fit the EUV data works well in TESS. What& #39;s going on? Optical variation was a prediction of the original metal spot model used to explain the EUV variation- but so was changing metal lines, and we ruled that out with Hubble 5/7
Other explanations include orbiting gas clouds, or (my personal favorite because Rule of Cool) a magnetic flux tube between the star and an orbiting metallic planetary core https://arxiv.org/abs/1906.08273 .">https://arxiv.org/abs/1906.... But working out which needs better data, and preferably in the EUV... 6/7
So suffice to say, I have at least one more paper to write about this star... 7/7 https://twitter.com/astrodave2/status/1243232084568748039">https://twitter.com/astrodave...
