Re: re HD 155229

[Michael Koppelman <lolife@bitstream.net>]

I finally got a look at the TASS data for this thing and, boy, 
this may or may not really be variable. The standard deviation 
for all the V magnitudes is only 0.0346. For each night is it 
0.02. The difference in the average magnitude between the two 
nights is only 0.06. If you average 4 observations at the 
beginning and end of each night, though, the first night it 
brightens by 0.025 mags and the second night it brightens by 
0.09 mags. That's 0.013 mag/hr the first night and 0.078 mag/hr 
the second night.

Because it is as bright as it is, though, we should be able to 
get fairly precise measurements. There's only one way to find 
out! If the weather holds I'll have some data of this tonight.

Cheers,
Michael K.

On Wednesday, August 7, 2002, at 09:51  AM, jg wrote:

> I've been kindly provided with a more rigorous spectral type for this
> star of F5 III.
>
> Also I note that _all_ the observations for it (both in V and I) are
> flagged as saturated, and as the range on any one of the two 
> observation
> nights is barely 0.1 magnitude I'd start being dubious.  Granted the
> mean mag on the two nights is different enough to make one feel that
> different parts of a varying light curve are being sampled.  
> Trouble is,
> I'm getting different signals on this.  Michael R.'s post stating
> calibration by Tycho for photometry suggests to me internight mean mags
> should be comparable, after all it's calibration by the same stars
> which'll suffer whatever the target star is suffering re environment
> and/or instrumental effects. Tom's post implies internight mean
> magnitudes aren't necessarily comparable.  I suppose both cases are
> true, so Michael R.'s statement just needs an error range adding to it
> (?????)  The low full amplitude for HD 155229 suggests it'll fall below
> the limit of that error range.