[vsnet-chat 4689] Re: re Bernhard Variable 92

[Klaus Bernhard <kl.bernhard@aon.at>]

Hi John, 

at the beginning of my survey members of BAV and I have made additional 
observations of a few new "SR"-variables (for example
GSC 1062-92, IBVS 4540). All of them turned out to show cyclic 
variations, of the kind which is described in the IBVS 5041 about
25 SARVs.
Except of one, BrhV89, all other "SR" variables showed variations
during the 1-2 months of survey-observations, which could be interpreted
as parts of sinusoidal variations, but I know this is a rather
"weak" argument. 
So it seems that irregular variability of type "L" is rather the
exception for those small amplitude red variables, which I found 
during my survey.
Of course I recognised also some red variables with larger amplitudes,
but all were known Mira variables. 
Because this preliminary description "SR" is also accepted by IBVS, 
I see no really problem to use it at the moment.
And finally there exist some other examples even for short period variables,
which are publicated and taken into GCVS without known
periods (example: the RR-Lyrae variable V576 Her).

But I have to say, that this is only my personal view as an 
amateur astronomer and not as an expert in red variables. 
I would have no problem to use other preliminary descriptions for 
such red variables, if it is necessary.

Best wishes,

Klaus Bernhard 
 

crawl@zoom.co.uk schrieb:
> 
> Hi Klaus, et al
> 
> Unfortunately there is a predilection in many quarters nowadays to class
> stars as type SR without any indication whatosever of cyclicity within the
> data.
> 
> Most people are classifying stars as SR when they should be classifying
> them as L ... ...in fact in some cases, where no hint whatsoever of any
> form of colour information exists, or the colour is around or equivalent to
> B-V of about 1 ish, the objects should simply be classed type I.
> 
> It should also be noted that although type L is a bit of a grabbag class
> for objects that are not as yet sufficiently studied to be able to be more
> properly classified, there are some LPVs with well known lightcurves that
> actually remain type L because they show no regularity, whether full or
> semi, within their behaviour.  (Trouble is, I can't remember one offhand :( )
> 
> As I've said before, a high amplitude slowly varying red star is nearly
> always going to be a Mira, though I suppose there's always a chance of an
> RCB star being stumbled across, but a low amplitude slowly varying red star
> can be one of several things, even if evidently an LPV.
> 
> Variant opinions welcome.
> 
> Cheers
> 
> John
> 
> John Greaves
> UK
> 
> At 20:19 02/08/01 -0700, Klaus Bernhard wrote:
> >Dear John, Dear colleagues,
> >
> >I also think, that both indications (B-R from USNO A2.0 and the
> >apparently slow variation, deduced from about 10 observations
> >in different nights within 1-2 months), which I take for classification
> >as a "SR"-variable are not unambigous.
> >If a "SR"-variable would be in fact a short period variable,
> >there could arise wrong B-R values, even if the epochs of the plates
> >differ only few days.
> >So I always mention in the VSNET-postings, that the colour and the
> >apparently slow change in brightness "suggest" a SR-variable.
> >
> >But I see, especially because of the X-ray source BrhV84
> >(a "SR-variable" transformed in a likely short period variable) that I
> have to write instead of
> >"Other types of l o n g period variability cannot be excluded"
> >in future
> >"Other types of variability cannot be excluded"
> >in my VSNET-postings.
> >
> >Best wishes,
> >
> >Klaus Bernhard
> >
> >>
> >> The epochs of the USNO A2.0 plates that this variable appears upon are
> >> dated 1979 for the blue one and 1984 for the red one.
> >>
> >> Using magnitudes from two totally different epochs for an avowedly variable
> >> object in an attempt to decide a colour index and subsequently a
> >> variability class is a somewhat problematic exercise.
> >>
> >> John
> >
> >

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