[Aavso-photometry] u crt sequence suspects! new obs

[Yenal Ogmen]

Hi all,

The following is the single observation of the field,
performed last night.

AAVSO label, JD, OYE Mag, Error
130, 2454592.29256, 14.035, 0.062
127, 2454592.29256, 14.300, 0.025

Clear Skies.

	
--- Richard Huziak <huziak at sedsystems.ca> wrote:

> Hi Yenal,
> 
> Sure - that would be nice. If I was forced to decide
> now, I'd say the 
> star is NOT variable, but you never know.  If you
> can, run at least one 
> all-night time-series.  Then after that, spot hits
> of 4 or 5 images per 
> night will suffice :-)
> 
> rick
> 
> Yenal Ogmen wrote:
> > Richard,
> >
> > I can observe the field here, and I will as long
> as
> > possible. I will post my results here.
> >
> > --- Richard Huziak <huziak at sedsystems.ca> wrote:
> >
> >   
> >> Yenal, Arne, et al.
> >>
> >> I've imaged the U Crt field over 6 evenings
> spanning
> >> the last month and 
> >> once last fall, since someone had questioned the
> >> field in May 07.  The 
> >> V-data below is untransformed and non-corrected
> for
> >> high airmass, but it 
> >> clearly shows that this field is really screwy.
> >> (Many fields done in 
> >> this era had strange 'photometry').  Besides 0.2
> or
> >> 0.3 errors in the 
> >> brighter stars, this field falls off at the low
> end,
> >> being a full 
> >> magnitude out with fainter stars.  (Again,
> typical
> >> of some of the charts 
> >> from then).  As Arne says - there will be a big
> >> 'adjustment' with his 
> >> new calibration.  However, my worst star is
> indeed
> >> the old '12.7' star. 
> >> Scatter is pretty severe over the 6 nights and
> there
> >> is a possibility 
> >> the star is somewhat variable (around 0.1 mag),
> but
> >> further photometry 
> >> is needed to confirm this.  Since the chart is so
> >> far off, I under 
> >> estimated what exposures I needed at for the low
> end
> >> stars - those data 
> >> have an SNR of around 20, so I can't conclude
> either
> >> way if the star is 
> >> variable or not.  Maybe Arne's images will sort
> this
> >> out for sure.  The 
> >> field is too far south for me, and with my
> >> brightening spring sky, I 
> >> can't follow the field much longer.
> >>
> >> rick HUZ
> >>
> >> AAVSO Mag    HUZ mag    Err    # Nites    Notes
> >>
> >> 11.0    11.302    0.012    6   
> >> 11.4    11.355     --     --    Reference star 
> >> (Arne's improved value = 
> >> 11.358 (0.012)
> >> 11.9    12.036    0.004    1   
> >> 12.1    11.774    0.002    2   
> >> 12.3    12.770    0.008    2   
> >> 12.5    11.879    0.010    2   
> >> 12.7    14.305    0.069    6    was suspect
> >> 1107-06B; 14.349 if best 4 
> >> nights used (Arne 14.274 (0.012))
> >> 13.0    14.058    0.027    5    Arne 14.038
> (0.016)
> >> *S UCrt    13.068    0.021    6    U Crt's
> companion
> >> to S
> >>
> >>
> >> arne wrote:
> >>     
> >>> Yenal Ogmen wrote:
> >>>   
> >>>       
> >>>> Hi all,
> >>>>
> >>>> As you may know, one of U Crt sequence stars,
> >>>>         
> >> "127
> >>     
> >>>> Comp S" is in the suspect list. A few hours
> ago,
> >>>>         
> >> when
> >>     
> >>>> I tried to do photometry of U Crt with comp
> star
> >>>>         
> >> 130
> >>     
> >>>> (GSC 4928:41) I got approx. 1 mag brighter
> result
> >>>>         
> >> than
> >>     
> >>>> the expected value, observed from other
> >>>>         
> >> observers' obs
> >>     
> >>>> at around the same time. Therefore I used 114
> to
> >>>>         
> >> get
> >>     
> >>>> reasonable estimate. Anyone know anything about
> >>>>         
> >> this
> >>     
> >>>> star (GSC 4928:41)? It is neither in the
> suspect
> >>>>         
> >> list
> >>     
> >>>> nor in VSX.
> >>>>
> >>>>     
> >>>>         
> >>> I've observed these stars multiple times in the
> >>>       
> >> process
> >>     
> >>> of calibrating this field from Sonoita Research
> >>>       
> >> Observatory.
> >>     
> >>> None of them are variable to the best of my
> >>>       
> >> knowledge.
> >>     
> >>> However, the chart photometry is far in error. 
> >>>       
> >> This is
> >>     
> >>> one of the fields that will change with the
> >>>       
> >> upcoming
> >>     
> >>> compDB/VSD update.  You can see this by clicking
> >>>       
> >> on
> >>     
> >>> the "Comparison Stars" link, where there are
> lots
> >>>       
> >> of
> >>     
> >>> comparison stars shown in the table, but with no
> >>> accompanying photometry other than their label.
> >>> Remember, the October 2007 update was only for
> >>>       
> >> those
> >>     
> >>> stars that did not change by more than 0.2mag
> from
> >>> their labels - so you can be sure that most of
> the
> >>> U Crt stars are going to change dramatically!
> >>> The old photometry came from a preliminary chart
> >>>       
> >> from
> >>     
> >>> 1977, with a photometric sequence from WML and
> >>>       
> >> LEH.
> >>     
> >>> The new photometry for the three stars that
> Yenal
> >>> mentions are:
> >>>
> >>> label  V      Verr
> >>> 114  11.358  0.012
> >>> 127  14.274  0.012
> >>> 130  14.038  0.016
> >>>
> >>> This kind of error is exactly why we are
> updating
> >>>       
> >> the
> >>     
> 
=== message truncated ===


Yenal Öðmen
  Green Island Observatory Homepage
www.geocities.com/yenalogmen 
Geçitkale 
North Cyprus



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