Re: more GSC 748-1618

[Michael Koppelman <lolife@bitstream.net>]

I have an astronomy textbook and it has an idealized light curve of RR 
Lyr and it has a similar bump prior to the maximum. I went a-lookin' 
for more detailed light curves of RR Lyr and found one in a paper 
entitled "The Blazhko Effect of RR Lyrae in 1996" by Smith et al 
(2003PASP..115...43S). The light curve rises a little then dips down 
before it rises to maximum. Another curve of RR Lyr is in "Light Curves 
of Variable Stars" (Sterken & Jaschek) on page 84.

For GSC 748-1618, Arne got B-V (at minimum) of 0.72. V-I at max is 
around 0.75 and at min is at 0.87. This seems to imply a G-type star.

RR Lyr, on the other hand, is described by SIMBAD as having B-V=-0.59 
and type F5. Their B-V seems completely wrong to me. According to 
SCHOENEICH et al (1979IBVS.1557....1S) B-V is more like 0.178 at 
maximum. I don't know how RR Lyr could be as blue as B-V=-0.59 and yet 
be described as an F5 -- isn't that way too blue for F5? VizieR 
catalogs generally have B-V ~ 0.4 or so for RR Lyr.

So what I'm pondering is: this star is much redder than RR Lyr. It has 
a similar shape to RR Lyr, but the "bump" shape is much more evident in 
I than V. It seems to me that this star has a "red" overtone.

This star is situated in the Orion arm of the Milky Way so I suppose it 
is possible there is a lot of reddening?

Cheers,
Michael Koppelman