[vsnet-sdor 13] (fwd) Re: HD 5980 rapid fading

[Taichi Kato <tkato>]

From owner-vsnet-chat@kusastro.kyoto-u.ac.jp Thu Oct 19 07:00 JST 2000
From: Fraser Farrell <fraser@trilobytes.com.au>
Date: Wed, 18 Oct 2000 21:55:31 GMT
To: vsnet-chat@kusastro.kyoto-u.ac.jp
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[edited]
> I am convinced that there will be another eruptive event in the near
> future.  In the case of the data you sent, however, I have calculated=

> the orbital phases using the ephemerides P=3D19.266 and T_0=3D2443158.=
7,
> and find that your observations correspond to the orbital phases betwe=
en
> 0.2 and 0.4, which coincide (at 0.36) with the eclipse of Star A (the =

LBV/eruptor)
> by Star B (presumably the original WR star), although a drop by 0.7mag=

> does seem a LARGE drop for visual magnitudes; I don't have my data her=
e,
> but I think that the usual amplitude of the light curve used to be aro=
und
> 0.3 mag.=20
[edited]

During the 1994 outburst HD 5980 reached mag 8.5-9.0 =96 not bad for=20=

something ~200,000 lightyears away! - and was showing eclipse amplitudes=
=20
of about 1.0 mag to visual observers. I believe the current ephemerides =

were deduced from observations of this event? =20

The VSS RASNZ has issued a chart for HD 5980; or you can use Mati Morel'=
s=20
"Visual Atlas of the Small Magellanic Cloud". But this is not an easy=20=

system to observe: HD 5980 is enmeshed in nebulosity, so are many of the=
=20
comparison stars, and they are all in a densely-populated part of the=20=

SMC.

Still, it is exciting to be watching a variable in another galaxy with m=
y=20
small telescope...


cheers,
Fraser Farrell

=20

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