Re: GSC 540-84

[Michael Koppelman <lolife@bitstream.net>]

On Monday, October 6, 2003, at 11:04 AM, Arne Henden wrote:

> Why do you feel this is an RRc star?

Patrick Wils and John Greaves originally expressed that they thought 
this was an RRc. I showed my light curve to a friend whose girlfriend 
is a grad student working with Horace Smith and they said:

>   I asked my girlfriend to ID that variable you had the light curve for
> (her specialty is RR Lyraes).  She discussed it with Horace Smith (her
> adviser who literally wrote the book on RR Lyraes) and they agree that 
> it
> is an RRc type variable and that the notch in the peak of the light 
> curve
> is real and of astrophysical interest.  The fact you can see the notch 
> is
> an indication that you're doing a pretty good job with the photometry.

I had double-checked it over the weekend and the small amplitude and 
short period and general shape are similar to the RRc stars. 
Furthermore, the relation I've discussed earlier about the amplitude in 
B and period P giving a good estimate of the absolute magnitude Mv is a 
relation that only works with RRab stars. This relation yields 
nonsensical results with this star. The lightcurve, though is a bit 
asymmetrical and has the prominent notch prior to maximum, so the ID as 
an RRc does seem a bit weird. That whole RRab, RRc system is a bit 
weird, though, which is perhaps why Alcock, Welch et al have gone to 
the RR0, RR1, etc. system.


Michael