From: njzy@vax5.cit.cornell.edu (T. Joseph Lazio, Cornell University)
Newsgroups: sci.astro
Subject: Re: Supermassive stars and HD limit (was Big Bang...)
Date: 23 Jul 92 08:29:22 EDT
Distribution: sci
Organization: Cornell University

In article <buell.711828426@phyast.nhn.uoknor.edu>,
buell@phyast.nhn.uoknor.edu (Jim Buell) writes: 
> njzy@vax5.cit.cornell.edu (T. Joseph Lazio, Cornell University) writes:
> 
>>In article <BroBAA.Bp7@well.sf.ca.us>,
>>metares@well.sf.ca.us (Tom Van Flandern) writes: 
>>> 
>>>      I was using the Crab Nebula pulsar as a possible example of a 
>>> transition case.  If the source body is small enough, after collapse we 
>>> get a neutron star/pulsar with radio jets.  It is flying away, and will 
>>> eventually leave the galaxy.  Now scale this up several orders of 
>>> magnitude to the case for a supermassive star.  Is it in any way strange 
>>> that, when supermassive stars collapse, they are ejected from the galaxy 
>>> with high speed, and develop radio jets of their own?  The cases look 
>>> parallel to me.
> 
>> Secondly, in reading your paragraph above, I see it making two, testable 
>> predictions. 
>> I)  When "normal" stars collapse, the result is a supernova.  When these 
>> putative supermassive stars collapse, they should produce 
>> super-supernovae.  Presumably these super-supernovae could be distinguished
>> in some fashion from the "run-of-the-mill" supernovae.  What would the 
>> distinguishing characteristics be and have any super-supernovae ever 
>> been observed?  I can think of one characteristic:  The absolute 
>> magnitude.  Surely these super-supernovae would be much brighter than 
>> regular supernovae; have there been unusually bright supernovae reported?
>> (By unusually bright, I would suspect a few to several magnitudes, not 
>> merely 0.1 magnitude or so [remember this is in the absolute magnitude].)
> 
> Actually you have to be careful with trying to make a connection between
> the optical luminosity and the mass of the progenitor star. The type II
> supernovae, which are associated with core collapse of massive stars, 
> release most of their energy as neutrinos. The neutrinos from SN1987A
> carried away approximately 99% of the energy.     
> 
> The brightest known supernovae are the type Ia supernovae. This type of
> supernovae is believed to be associated with white dwarfs in binaries. 
> These supernovae are approximately 2 magnitudes brighter than the type
> IIa SN. The type II SN have a large dispersion in magnitude, while the
> type Ia may have no dispersion in magnitude (AJ 100, pg 530).  

 Hmm, yeah, I had not considered this.  So maybe my testable prediction
 I) does not pan out.

>> II) Some QSOs are seen well removed from galaxies.  Has there ever been 
>> a case in which a supernova was observed being well removed from the 
>> outer extent of a galaxy?  (I mean by, say, a few arcminutes, not merely
>> on the outer edge of the optical emission of a galaxy.)
> 
> The type IIa SN are strongly associated with HII regions. There is
> evidence for this in measurements of the positions of SNs and HII
> regions in external galaxies (I have no reference handy at the moment).
> The type IIa SN seem to occur very close to HII regions and these are
> the massive ones. I don't believe that any type IIa SN (at least good
> ones, I mean ones that are definitely type IIs). have been observed 

 This is exactly what I was trying to describe.  Type II supernovae are
 "strongly associated with HII regions."  Type Ia supernovae show a more
 spherical distribution around galaxies, but are still well associated
 with galaxies.  However, QSOs are seen many arcminutes from galaxies;
 are there supernovae reported this far from galaxies?

-- 

 T. Joseph Lazio                | Why relativity? and Why  
 514 Space Sciences             | turbulence?  I really believe   
 Ithaca, NY  14853              | [God] will have an answer for the
 (607) 255-6420                 | first [question].
 lazio@astrosun.tn.cornell.edu  |   -- W. Heisenberg, on his death bed
ICBM:                           |
 42 deg. 20' 08" N              |              STOP RAPE
 76 deg. 28' 48" W              |