SW UMa comparison stars: correction and addenda

(vsnet 616, Brian Skiff)

Bob Modic has kindly pointed out that the 1958-vintage AAVSO chart for SW UMa that I used [vsnet 614] has been superceded by one from May 1991 that includes photoelectric V results by R. Stanton. Since these data are not published, I was not aware of them. Mr. Modic also notes an error of mine that slipped by my proofreading, which was hurried in this instance, as well as some other points of interest.

First, I gave the wrong GSC name and position for the mag. 13.5 star observed by Misselt, which was the last star in the list. This should be: GSC 3798-0481, at 8 36 52.8 +53 29 24, located about 1'.5 east-northeast of SW UMa. I believe Kato-san noted this error, and his chart issued yesterday is correct.

The mag. 12.14 star GSC 3798-0491 is NSV 4147. This was observed by E. Zinner (1939 Astron. Nach. 268,44), who reported that most of his visual observations fell in the magnitude range 11.4-12.0 (he had originally mistaken it for SW UMa), but also a range of only 13.1-13.5p on photographic plates. This small range, in addition to my two consistent observations, suggest that this star is probably _not_ variable. Also judging by the literature, nearly all of Zinner's suspected variables are constant, or do not have significant amplitudes. Since this star is probably contained on many CCD images of the SW UMa field, it should be straightforward to test for constancy without taking any new data. Could someone have a look?

Bob also notes that the star GSC 3798-0705 (mag. 11.41) is marked on the new AAVSO chart as a suspected variable. My two observations are somewhat inconsistent (delta-V = 0.02), but not enough to indicate obvious variability. Again, perhaps "vsnet" observers already have enough CCD data to test for variability. Do not use the star ~3' south as a comparison---this is the eclipser EQ UMa! The star's color is that of an early-K giant, and it is entirely reasonable the star could be chromospherically-active, and hence somewhat variable.

Sorry for the mix-up and waste of bandwidth to set things straight!

\Brian Skiff (bas@lowell.edu)

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