[vsnet-chat 5007] Re: [vsnet-obs 37562] Eta Carinae is not brighter

[Bish Ishibashi <bish@space.mit.edu>]

Howdy Stan,

I wouldn't so readily dismiss the idea of eta Car (not the nebula)
brighten in a short period of time. What you have described is 
reasonably correct so as long as the brightening involves its nebula
as well as the central light source. For an LBV eruption, it's 
conceivable that the star's diameter expands out (as it cools 
and becomes redder) while the total luminosity increase (as its
surface area increases). In the case of a brightening by 0.5 astronomical 
magnitude, the star needs to increase its flux by 1.6 times or so.
That implies, if purely based on apparent stellar size, the increase
in diameter by 25% or so in one day. Yeah I agree that's pushing the limit;
but I wouldn't know for sure if it's improbable either (BTW I think it
is probable).  

Of course, if the brightening were real, I'd expected the surrouding 
nebula to be affected by the time scale that Stan was describing. So 
maybe someone wants to monitor eta Car with a moderately high-spatial 
imaging cameras. 

Finally I second Stan on the issue of how difficult to observe eta Car
with naked eyes. I will never be able to do it (nor would I trust 
myself for it), but many of you seem to manage that. And that's pretty 
impressive to me. 

Regards, 

Bish

PS. Sorry about the loss of your friend. 

-- 

"Bish" K. Ishibashi, Ph.D. 

Massachusetts Institute of Technology
Center for Space Research                 e  bish@space.mit.edu
77 Massachusetts Ave. NE80-6011           
Cambridge, MA 02139

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