in both pdf and .txt format joe p
Attachment:
stars312.pdf
Description: Adobe PDF document
March 12, 2017. Hi CBAers, Unless Christian or Enrique protests mightily, time to end the YZ Cnc campaign, or demote to once-a-week status. CN Ori is also at the end of the line. Time to quit. Nice result: all the previously published orbital periods appear to be wrong (in the third decimal place). The reason is subtle: in this ever-on-the-move star, the phasing of the orbital wave is not completely stable - it depends on brightness. Could this be a consequence of changes in disk size? A tempting interpretation... but one which awaits more careful analysis. We have long-term programs going om FS Aur and BY Cam. Many others too of course, but these are at the end of their observing seasons... and end-of- season runs are of special value because they help bridge the gap to the next observing season. So on some clear nights when you can get a long-ish run, have a go at these stars. This self-expires about April 1 (can't get blood from a turnip). Shawn Dvorak has started up the AM CVn season, and that's definitely a star for high-priority coverage over the next month. We need just one more high-quality timing to get a superb 24-year ephemeris. But each good- quality timing takes a week or more of coverage, because there are two stronger signals - the 1051 s and 1011 s superhumps - which have to be subtracted in order to isolate the 1028 s orbital signal. It's not that difficult to do this, but it does require a lot of concentrated runs - as long as you can go on it, and for a few weeks on end. I've written up our paper on the recurrent nova IM Nor. It appears to be a great match for T Pyx, which is mighty encouraging since T Pyx otherwise stands alone - no relatives! - in the CV zoo. But now that Norma season has rolled around again, I really want to get a few 2017 timings of the eclipse. It's 19th magnitude, so is probably a project for Gordon and Berto only (who have been able to get good data on it in the past). T Pyx. Now near the end of its observing season... and for the same reason cited above, a good time to get some long runs, to pin down the cycle count. Not that it's uncertain, but since the period is changing (mirabile dictu!), we have to keep vigilance on it. Berto has gotten one late-season run - another 3-5 will end its observing season nicely. NY Lup. Beginning of observing season for this DQ Her star. Beginnings are just as critical as endings, for the same reason. A few runs now would be great. Watch out for the contaminating neighbor star. Consider this list to be ADDITIVE to Enrique's list. He's more up-to-date than me concerning current targets, especially the DQ Her stars, which he tracks closely. I heartily concur in recommending EI UMa as a great northern target now. I've got the AAVSO/SAS June meeting on my travel schedule, and hope to see a bunch of you there! joe p
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