[vsnet-chat 4680] Re: [vsnet-newvar 1030] re Bernhard Variable 92

[crawl@zoom.co.uk]

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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