Date: Tue, 14 Mar 2006 16:24:36 +0100 From: Hubert Hautecler the oddball cases, especially those with close companions. So >as you might have expected, I have looked at this close pair. > >I have a BV image set from 2001 December 19, at the time when Z Tau >was about the same brightness as its neighbor to the NE (fading >to minimum); and another from December 29, 2003, again about the same >brightness (but on the rise to maximum). A 3x3arcmin section of the >http://www.aavso.org/tmp2/ztaub.jpg >The separation is about 5.3 arcsec, and it is unquestionable that >the flat bottom is caused by mistaken observations of this companion. >However, to resolve the pair with amateur equipment will require >good pixelization and excellent skies, along with large aperture if >the range really is 7 or 8 magnitudes as Bob suggests. On the >other hand, I do have good calibration of the companion, so you >can measure both stars as a blend and we can subtract out the >contribution from the companion using Lew Cook's Nemisis spreadsheet. > >I'll see if I can get new data at SRO and NOFS during the current >minimum. CCD observers should give it a try, at least until Z Tau >brightens above the magnitude of the companion. >Arne > >Bob Wing wrote: >>Date: Monday night, March 13-14, 2006 >>Dear Rick, Erwin, et al., >> >>The real problem is that if Z Tau gets much fainter than the companion, >>as it probably does, then only one star is visible, at approximately >>the right place, and the companion is likely to be misidentified as >>plot the companion on the chart, if the scale permits. Then if the >>observer sees only one star, he/she will have to think consciously >>about which one it is. Erwin mentioned that the companion is shown >>This is of some importance because Z Tauri is an interesting star. >>its mean light curve with an extraordinarily long period of 495 days >>The GCVS (I'm looking at the 4th edition, 1987) gives its period as >>type as S7.5,1e, which presumably refers to a phase near maximum light. >>are present in the spectrum in addition to the dominant TiO bands). >>Interestingly, this is very similar to the description of Chi >>visual amplitude of any Mira on record (10 magnitudes!). In fact, >>they generally >>V = 17 or even 18. It would be nice to know. Observing it at minimum >>will be challenging, but doable with a CCD with sufficient scale to >>separate the two stars (I don't know the separation). >>Mira near minimum light provides an opportunity to observe an extremely >>cool (by stellar standards) gas, which is bright enough to be observed >>spectroscopically (at least in the infrared). At low temperatures one >>sees molecules that are not present at warmer phases. And with the >>molecules that have never been seen in any star. It was in just such >>Miras) that bands of zirconium sulfide (ZrS) were first identified. >>So let's get after Z Tau and see how faint it actually gets. I >>just downloaded Bulletin 69 (Predictions for 2006) and see that Z >>Tau (0546+15A) is listed as "urgently in need of observation." It >>had a predicted min last January 19, so it won't have another one >>until April of 2007. But it's still faint now, and there should >>still be a chance >>this year, before it goes behind the sun, to observe it while it's >>significantly fainter than its companion. >_______________________________________________ >