Literature Review #2: Is RR Tau a binary?

On the Nature of Cyclic Light Variations in UX Ori Stars
Grinin et al., Astronomy Letters

Vladimir Grinin is a name that often pops up when looking into UXors. He has been studying them for decades which is quite an advantage in variable star research. He had his his co-authors conducted decades long photometric monitoring on many UXor type stars that produced a series of papers. This paper is the first in the series and includes the results for RR Tau.

They observed RR Tau for 673 nights spanning 30 years. They found evidence of possible periodicity on timescales of ~8.6 and ~3.4 years. As far as I know this is the first discussion of long photometric variability in UXors and something I haven’t really seen discussed until the Maria Mitchell paper. It is interesting to me that our timescales are so different. The long term variability that we discussed in our paper was on the order of 100 days but Grinin et al. are talking about many years. I doubt that this has anything to do with the mechanism of variability that I want to look into for my thesis but it is fascinating to add another layer of complexity to this stellar system.

The change in continuum light over time.

The above figure is from a small review paper they wrote summarizing all their results.

The authors attribute the variation to binarity mostly because it is periodic and because the percentage of binary stars among Herbig Ae/Be is high. From what I can tell from their paper that they don’t directly attribute the periodicity to the companion star passing infront but rather the companion star is disrupting the the column density of the circumstellar disk. They go onto assert that the a binary system accounts for the short term activity that characterizes UXors also because of disruptions. This possibility could be relevant to my investigation on the medium term timescale.

I don’t understand the differing timescales they report, I don’t see that in the light curve. I’m going to read the other papers in the sereis and see if they shed so light on it.

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