[vsnet-chat 4423] Re: HM CMa

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

Hi Taichi,

Your question raises some interesting points. When HL CMa was first
mentioned as a DN star we were asked to make a sequence for the VSS RASNZ.
This was a rather difficult task as the scattered light from Sirius caused
problems with the background. But we overcame this and produced quite a
reliable sequence: +/- 0.03 in V. This is, however, not the one in use as
the VSS adopted a sequence prepared by someone a little later for the AAVSO.
This had some inconsistencies as I don't think the background was handled
adequately. We didn't bother to help with sequences after that and I'm not
sure if the original AAVSO sequence is still in use.A number of the visual
observers complained about the AAVSO sequence so if it hasn't been revised
it probably needs it.

The flare star discovery dates from not long after this in the days of
sequential photometry. But the field is so dominated by the light from
Sirius that even a slight bit of haze would cause flare-like excursions in a
single channel photometer. So unless it was dual channel photometry I'd have
to be a bit sceptical about the discovery. We were using a 50cm telescope
and the photometry limits were about V = 14 with UBV filters with +/-0.005
precision in other fields. Wish I could get this with the CCD!

Regards,
Stan




----- Original Message -----
From: Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>
To: <vsnet-chat@kusastro.kyoto-u.ac.jp>;
<vsnet-flare@kusastro.kyoto-u.ac.jp>
Sent: Sunday, May 06, 2001 6:55 PM
Subject: [vsnet-chat 4415] HM CMa


> HM CMa
>
>    Has anyone succeeded in confirming the flare-star nature of HM CMa,
> close to Sirius?  I had seen many times this field when observing HL CMa,
> but never saw a brightening of HM CMa.  Is the frequency of flares is
> extremely low?
>
> Regards,
> Taichi Kato
>
>

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