[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: HD 145913



Doh, my ISP filtered this message as spam. I've fixed that now. I want 
to thank Dr. Kato for this information. (I'm not hip to the "Kato-san" 
cultural references, so please educate me if I refer to people 
incorrectly).

So assuming for a second that the flicker I recorded is not a result of 
systematic problems on my end, it is common that a period would be 
apparent or can nearly random noise produce things that look like 
periods in Fourier analysis?

I will get Kato et al. (2002) PASJ 54, 1033.

Cheers,
Michael Koppelman


On Thursday, May 8, 2003, at 09:43 PM, Taichi Kato wrote:

> Re: HD 145913
>
>> I seriously doubt it is a CV, with a quiescent magnitude of ~7.7,
>> since that would imply naked eye visibility if it ever went into
>> outburst.  A5 is also quite red if we were dealing with a 
>> run-of-the-mill
>> CV.
>
>    This star has a good HIPPARCOS parallax measurement.  At this 
> distance,
> the absolute visual magnitude is about +1.9, consistent with the
> main-sequence value of the corresponding spectrum.  So this is not a 
> CV.
>
>> "Virtually all CVs flicker erratically on timescales of 1-3 minutes, 
>> so
>> if your time resolution is much worse than ~40 s, you become blind to
>> this and it appears merely as unwanted noise (which can be quite 
>> large,
>> even ~0.2 mag)."
>
>    Please remind that CV flickering has a power-law type time-variation
> (see e.g. Kato et al. (2002) PASJ 54, 1033 and references therein).
> This means (to a certain limit) the amplitude of variation becomes 
> larger
> at longer time scales, and flickering is present at any sampling rate.
> (It would be interesting to see integrated light curve of artificially
> produced power law-type noise component).  If there is a typical time
> scale, such a phenomenon is usually called quasi-periodic oscillations
> (QPOs) rather than simple flickering.
>
> Regards,
> Taichi Kato
>
>