Re: GSC 540-84

[Doug Welch <welch@physics.mcmaster.ca>]

TASS'ers,

"The Blazhko Effect" has been historically associated with amplitude
modulation. However, we have found both amplitude and phase modulation
in our large RR samples, so it is perhaps incorrect to deduce that the
underlying phenomenon only causes amplitude modulation. The phase
modulation issues, especially long-term ones, are complicated by the
fact that most RR stars have some degree of period variation due to
unknown causes. These changes are usually not purely periodic or
monotonic.

Cheers,
Doug
 
On Mon, 2003-10-06 at 12:04, Arne Henden wrote:
> Why do you feel this is an RRc star?  I don't recall indicating
> that I thought it was RRc, only generic RR.  All RRc (though
> Doug will probably correct me!) have sinusoidal light curves
> with no bumps or wiggles, and that is not what you are showing.
> If it is RRab, then Blazhko is common.
>    Also, I don't think you are using correct terminology when talking
> about "period modulation".  These stars are all pulsating with
> constant periods, just sometimes more than one (RRd).
> Arne
> 
> Michael Koppelman wrote:
> > Hmm. I'll have to get used to your new terminology. I'm guessing that  
> > this star is what you describe as an RR0 type star, in that, according  
> > to Arne at least, it looks like there are not overtones, only the  
> > Blazhko effect. If I'm interpreting the new terminology correctly and  
> > understanding some of your conclusions correctly, it seems that the  
> > Blazhko effect is indeed rarer in stars pulsating in/with an overtone,  
> > which the RRc generally are.
> > 
> > Part of my confusion is: it seems to me that it could be hard to tell  
> > whether something is modulating in period or amplitude. If the primary  
> > period is much stronger, either case is going to look like a periodic  
> > alteration of the primary period. Am I correct that the Blazhko effect  
> > is an amplitude modulation and that the overtones you discuss are  
> > modulations in the period? I'm a musician so it's easy for me to view a  
> > complex wave as the sum of a primary "note" and overtones. The Blazhko  
> > effect, although I have more to read, seems to not be the sum of more  
> > than one "notes" but the actual modification of a single note?
> > 
> > Feel free to reply: "Go read more, Michael!"  ;)
> > 
> > Michael
> > 
> > On Saturday, October 4, 2003, at 05:32 PM, Doug Welch wrote:
> > 
> >> If you want to read the latest on statistics of RRc Blazhko's,
> >> check out our paper:
> >>
> >> "The MACHO Project Large Magellanic Cloud Variable-Star Inventory. IX.
> >> Frequency Analysis of the First-Overtone RR Lyrae Stars and the  
> >> Indication
> >> for Nonradial Pulsations"
> >> Astrophysical Journal, Volume 542, Issue 1, pp. 257-280
> >>
> >> http://adsabs.harvard.edu/cgi-bin/nph- 
> >> bib_query?bibcode=2000ApJ...542..257A&db_key=AST
> >>
> >> There is a similar paper for the RRab's currently in press.
> > 
> > 
> > 
> > 
> > 
> 
>