[vsnet-chat 1562] Re: On the query of "host galaxy" information

[Hitoshi YAMAOKA <yamaoka@rc.kyushu-u.ac.jp>]

I have handed Ms. Gheen's question below from Dr. Kato to make answer.

> I was also wondering how you know that something is a Super Nova.

Many supernova hunters are there in the world.  They are observing
galaxies, and if they find a new point source without movement on or
near to the galaxy, they guess it can be a supernova.

However, there is always a probability that it is really a foreground 
variable star in its nature.  To clarify this, the spectroscopical 
observation is needed.  Maybe as you know, the supernova is an 
exploding event, whose expansion velocity is well above 1,000 km s-1,
or sometimes reach 10,000 km s-1.  The spectrum of such expanding
object have some absorption or emission feature with very wide width,
which does not appear in that of (ordinal) variable stars.  

You can see the typical spectrum of supernovae are available at:

http://cfa-www.harvard.edu/cfa/oir/Research/supernova/spectra/sn98dh.gif

And, if you are interest to get a example of the accidental overlap,
please see: 

http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/DNe/sn1998di.html
http://cfa-www.harvard.edu/iauc/06900/06982.html
http://cfa-www.harvard.edu/iauc/06900/06983.html

, and the spectrum of 1998di:

http://cfa-www.harvard.edu/cfa/oir/Research/supernova/images/sn98di.gif

, which shows very different spectrum than that of SNe.

Sincerely Yours,
Hitoshi Yamaoka, Kyushu Univ., Japan
yamaoka@rc.kyushu-u.ac.jp

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