Re: HD 145913

[Michael Koppelman <lolife@bitstream.net>]

On Thursday, May 8, 2003, at 09:19 PM, Arne Henden wrote:

> 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.

Yeah, I mentioned CVs only because of this notion that some stars 
flicker on very, very small time scales (which this star may or may not 
be doing).

> My guess is that Mira's photometric estimate is in
> error or not being used correctly.

Why? I've heard people talk of errors being (S/N)^-1, which in this 
case would be like 0.00125. The 1-sigma in the comp star is 0.0045. 
That puts 3-sigma at 0.01. The thing is damn bright -- even a hack like 
me can get OK results with enough signal, don't you think? ;)

>  I presume you looked long
> enough to confirm that there could not be eclipses at John's
> period?

He gave a very rough estimate of 4.8 hours. I got about 2.6 hours, so 
no. He also mentions a 0.05 amplitude from Hipparcos, which is close to 
my amplitude of 0.04 (although I'm in R, not V).

> The TASS Welch-Stetson statistic is quite high, so I
> would look at the original data and see if there was any discrepant
> data that gave such a high value if the star is "constant" (at least
> within the error limits of Tom's camera).

The TASS data has a few points which look errant and a lot of points 
with a flag of 1. If you delete all of those you still get a standard 
deviation of 0.017 and and amplitude of 0.105, which is much more 
variation than I was able to demonstrate. Maybe it's worth another look.

Michael Koppelman