SCV Astronomy - PMDO Sky Survey - Odd 1

[SCV Astronomy] -- [SCV: PMDO Survey]

Here's an interesting combination of plates, a good example of "you never know what will turn up" ...

This is a nice red/green pair on a stack of plate 29's, magnification x2. It's a good pair, since the red and green blips are well rounded and very similar in appearance. Trouble is, the red & green images were taken a month and a half apart! But the separation of the pair is what you'd expect from a typical asteroid in only about 3 days.

I launched Guide7 and searched for roids anyway, and one came up right where I expected it: the red spot is 146 Lucinda, mag 13.0. But on the date of the green blip, Lucinda had zoomed off the plate.

Now, there was only one known variable star on this plate, and wouldn't you know it, it's exactly where the green blip was. I didn't bother looking for this star (V1083 Tau) originally, and almost removed it from the list, because the GCVS magnitudes are given in the J band. Infrared. No indication of what the visual magnitude was, and these infrared stars tend to be ancient red giants that could be 8 to 10 magnitudes fainter visually. Anyway, I found the blip on a few other November 2002 plates, and could see it fading in and out again. So apparently this infrared star (also known as IRAS 03410+0646) is observable in the PMDO Survey, but only when it's at maximum, around visual magnitude 13.

A pleasant surprise. While this star is not listed in the GSC 1.2, it is listed in the huge GSC 2.2 as N30233004721 magnitude 11.9(red), 15.8(blue) -- you can how faint it gets at bluer wavelengths! In the infrared its magnitude range is 6.0 to 7.4, and these stars often show the greatest changes in IR wavelengths. The catalog suggests that it's a Mira-type variable, even though it has a small amplitude, and gives no hint what it's period might be! Anyway, the lesson is that some of these fleeting blips are real. :-)