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Further message from John Greaves: === I forgot to think to do this at the time... Placing it in Orion OB1 allows an estimate of type based on the mean E(B-V) of 0.3 and a distance modulus of 8.5 for that Association. Tycho2 gives this object derived B-V 0.60, minus the E(B-V) of 0.3 gives 0.30, just about right for an F0 star I believe, which indeed the Henry Draper catalogue claims it is. Using Av = 3.3 E(B-V) (some say 3.2, some say 3.3) and the distance modulus of 8.5 and guessing at a maximum visual magnitude of around 10.8 from the vsnet pages' plot, then Mv = mv - dist.mod. - Av becomes 10.8 - 8.5 - 1.0, ie an absolute magnitude of 1.3, with 1.5 being right for an F0 giant. So, it seems to fit. If it was a supergiant it would have to be a lot further than the Orion OB1 association to appear at its maximum apparent magnitude, E(B-V) creeping up accordingly, which when used to correct the measured B-V (well, Tycho2 assessed) would cause the star to be somwhat earlier than the Henry Draper assessed F0. Oh..., a quick double check on the SRd code reveals that they can be either giants or supergiants, I must have been getting muddled with SRc (which are supergiants). So placing it in Orion OB1 doesn't help distinguish between the variability type possibilities at all. So I suppose the next thing is to assess the frequency of semiregular variables in the Orion (or any) OB1 association relative to that of YSOs ;^) Cheers John
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