[AZ-Observing] Re: Delta Sco Fading
- From: Jeff Hopkins <phxjeff@xxxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Wed, 11 May 2005 15:45:55 -0700
Thanks for your input Brian.
Yes! I noticed the JD comma instead of the decimal point after I sent
it the message. Too late then. I was still a bit fuzzy from the
night's observing.
Since I measure the UBV values I always state them. It's easy to do
the math to get the color index. I was surprised at how bright it is
in the U band. I plan to try again tonight (actually tomorrow
morning). The stars are low to the south so not ideal for photometry,
but at this latitude that' about as good as it gets for that system.
Check for Sebastian Otero's latest data at:
http://ar.geocities.com/varsao/delta_Sco.htm
On 1 April 2005 it was around V=2.1, but a few days ago (3 May 2005)
it was V=2.05 and increasing in brightness so my observations may
fall well within what might be expected. More observations will give
more confidence. There may be a brightening trend right now at least
that looks like a possibility from Sebastian's chart.
The B and thus (B-V) is interesting. The Yale Bright Star Catalog has
(B-V)= -.012 and (U-B)= -0.91, so indeed a (B-V)= +0.12 is strange. I
rechecked things and can find no error, but will check further. I
used alpha Lib (B-V)= +0.11 where as the YBSC has it as +0.15 which
makes things worse. The B readings were fairly consistent. Let's see
what tonight brings. It would be nice if someone else was doing B and
U band observations on it.
The system approaches the meridian around 00:30 (7:30 UT) which is an
odd time, I must stay up late as getting some sleep and waking up is
hard for me for a time like that. That means getting to bed around 2
- 3 AM. I know, I'm just getting old.
Jeff
At 13:58 -0700 5/11/05, Brian Skiff wrote:
>>> Delta Sco Results
>>> JD 2,453,501,8201 2453501.8201, yes?
>>> V= 2.028 SD= 0.006
>>> B= 2.144 SD= 0.008
>>> U= 1.262 SD= 0.018
>
> Since I'm a photometrist, I tend to think in V mags and colors,
>rather than separate magnitudes, so: B-V = +0.12 and U-B = -0.88.
>The usual colors of the star are B-V = -0.11 and U-B = -0.90, and
>V = 2.32. So evidently the star is still brighter than normal,
>and the U-B color seems the same, but B-V is much redder. Is that
>possible?
>
>\Brian
--
Jeff Hopkins
HPO SOFT
Hopkins Phoenix Observatory
http://www.hposoft.com/Astro/astro.html
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