[vsnet-chat 5766] Re: More on flare stars

["Stan Walker" <astroman@xtra.co.nz>]

Hi Federico,

I did a lot of flare star observing at Auckland Observatory from 1966-75.
Initially it was visual but the lack of success this way caused us to design
and build a photo-electric photometer which we used from 1968 onward.

Firstly, the stars are usually K and M dwarves - with flares more frequent
and more easily seen as the intrinsic magnitude gets fainter. UV Ceti is one
of the most active with some large flares at times. Proxima is also a flare
star. But there appeared to be no particular pattern of activity and on some
stars we observed up to 40 hours with no flare detection. This was using a
photometer with a detection capability of about 0.005 magnitudes. At other
times the flare activity was much more frequent. Since flares are
essentially random events it is a programme requiring a large network to get
useful data.

These stars are usually spotty so there was some success at obtaining
rotation periods of many - BY Draconis variables I think - but the
variations are usually too small for eyeball photometry. The radio people
are still working on some similar objects - RS CVn stars with short
periods - CC Eridani is one, where the visual measures in the form of CCD
measures provide light curves to help interpret their long wavelength
observations. This is probably a more useful area that the classical flare
stars - the RS CVn stars seem to have flares as well - but needs to be
organised. Random data is useless.

As a footnote there was some excitement about the possibilities of B type
stars showing detectable flares but although the visual observers claimed
some of these we could never verify these photoelectrically. Then there was
the group who claimed to have found high speed variations on W Crucis, a
massive eclipsing binary with a period of ~198 days! Regrettably, many of
the reported observations were spurious for a variety of reasons which can
easily be imagined. But, again from memory, one of the stars in the field of
HL CMa is reputed to be a flare star and was used in the original AAVSO
sequence.

Regards,
Stan

----- Original Message -----
From: "Federico Claus" <fedeclaus@hotmail.com>
To: <vsnet-chat@kusastro.kyoto-u.ac.jp>
Sent: Sunday, December 29, 2002 11:51 PM
Subject: [vsnet-chat 5765] More on flare stars


> Dear friends of Vsnet chat:
> Before Christmas, Sebastian Otero wrote that he was interested in
observing
> flare stars and he asked some interesting topics about these, from my
point
> of view, amazing kind of variable stars. All I know is that are dwarf
> stars(right or no?) with a strong magnetic activity. I usually go to a
solar
> observatory and I`m rather used to see flares in the Sun and to follow
their
> short evolution. But I wonder, what is to see a flare star like? Do they
> have any period or cycle? What kind of research can I do with my purely
> visual observations? Any profesional around, perhaps, investigating them?
> What`s the job of a flare star observer like? All you can tell me about
will
> be really useful.
> Thanks anyway and best regards to everybody
>
> FEDERICO CLAUS
>
>
>
>
>
> _________________________________________________________________
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