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Re: flares in Mira stars The following information is from John Greaves: Date: Tue, 3 Jun 2003 19:41:49 +0000 Subject: Flaring Miras' Literature I have read, albeit not to a very great depth, the following three referred to (in the Hipparcos Venice Symposium poster) papers on this matter: 1) Schaeffer ApJ 366, L39 (1991) - 14 stars are mentioned. Most are from photographic plates, taken a few days apart, with one plate out of these being claimed to show a rapid variation, often as not a _dimming_ is mentioned, not a flaring! These plates are old Harvard Patrol Archive plates or proper motion survey plates from the sixties (one in the forties) and were never intended as part of any photometric campaign. Independent checks on these plates are not going to readily be made. I know from experience that you do not have to only check the star in question on one image against the other, but also that the other stars on one image against the other. I'm not entirely happy with the low amplitudes of flaring being quoted from these non-photometric photographic plates either, mostly <1 magnitude. A _handful_ of visual observations are noted, apparently belonging to Albert Jones, a long term and reliable observer even for the dates quoted (fifties and sixties). But the flarings were not reported by Albert Jones, but apparently by others using his data. Just 3 instances for 3 stars, 1 instance per star. There is talk of some photoelectric photometry in which it was possible to double check against the check star to see if the variation was local to the star or instrumental/environmental etc. Interestingly again there are only a handful of observations noted, all of single events, twixt mid 1966 and mid 1967. Also they are attributed to only one observer, which in itself is not necessarily a problem, but independent confirmation always helps. It is also noted in the paper that various and wide evidence exists for flaring in CH Cyg, but that is no great surprise, considering it is a Symbiotic variable as well as a Mira. (In that context, I wonder why R Aqr isn't mentioned). Actually, I find the Schaeffer paper a "nothing" paper, though admittedly it is techinically only a "letter", as it has nothing very concrete in it, and is almost at a 'hearsay' level. Unless, of course, I've missed the main Schaeffer reference and this is another. R Trianguli, one of the photoelectric photometry candidates from Schaeffers' list has one sole hint of flaring in AFOEV lightcurves, but this could just as easily be a discrepant point, occuring as it does just prior to a gap in observations. On the other side of the matter, it does have a late M spectral type. It might well be worth adding to a Northern Hemisphere shortlist, along with R Aur and X Dra. 2) Maffei and Tosti AJ 109, 2652 (1995) This paper is not strictly applicable. The variations in question are "rapid" relative to the full cycles of the Miras noted, as the authors note, but are in the range of two to thirty days. Not exactly a flaring event in my book! Anyway, they are in highly seasonal near ecliptic Milky Way fields, and therefore probably aren't generally amenable to constant surveillance. There probably isn't much lightcurve data available for them anyway. The data in the paper is from near infrared _photographic_ survey work. Dimmings are mentioned as much as flarings yet again. 3) de Laverney et al A&AS 122, 415 (1997) de Laverney is also the prime author of the Hipparcos Venice Symposium paper, which is also of 1997 vintage. In fact only two stars out of the twelve Mira mentioned are said to flare. However, it is not clear which two from the wording of the paper. One may be R Oct, I am unsure. I have passed the data on to someone else better to judge (the data is available via ftp from the CDS). The data is however relatively sparse in terms of total amount, time between each observation run and nature of each observation run. CONCLUSION The professional published information on Mira flaring (and I've always interpreted flaring to be a word implying rapidity) is either anecdotal or not strictly relevant. Equally, it isn't always based on data that could be considered of the most rigorous photometric quality, let alone concerns with respect to the adequacies of the observing regimes' temporal baselines. There is no direct hard evidence out there of short term flarings of around 0.5 to 1+ , <2 mag in the visual. There is some anecdotal evidence, and some circumstantial evidence. The few light curves I have looked at are not clear enough to be sure of anything. In fact, lightcurves often look _too_ clean, so any discrepancies, real or unreal, are no doubt lost. There's an opportunity out there if observers are interested, although disproof being just as likely as proof I suppose not that many will be so, as ending up showing something unexpected isn't happening ain't as 'sexy' as showing that it is! Cheers John John Greaves
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