[vsnet-chat 3724] Re: HD 5980 rapid fading

[Fraser Farrell <fraser@trilobytes.com.au>]

[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=19.266 and T_0=2443158.7,
> and find that your observations correspond to the orbital phases between
> 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 here,
> but I think that the usual amplitude of the light curve used to be around
> 0.3 mag. 
[edited]

During the 1994 outburst HD 5980 reached mag 8.5-9.0 not bad for 
something ~200,000 lightyears away! - and was showing eclipse amplitudes 
of about 1.0 mag to visual observers. I believe the current ephemerides 
were deduced from observations of this event?  

The VSS RASNZ has issued a chart for HD 5980; or you can use Mati Morel's 
"Visual Atlas of the Small Magellanic Cloud". But this is not an easy 
system to observe: HD 5980 is enmeshed in nebulosity, so are many of the 
comparison stars, and they are all in a densely-populated part of the 
SMC.

Still, it is exciting to be watching a variable in another galaxy with my 
small telescope...


cheers,
Fraser Farrell

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp