From: buell@adagio.nhn.uoknor.edu (Jim Buell)
Newsgroups: sci.astro
Subject: Re: Supermassive stars and HD limit (was Big Bang...)
Date: 23 Jul 92 13:33:58 GMT
Distribution: sci
Organization: Engineering Computer Network, University of Oklahoma, Norman, OK, USA

Some more corrections of my dumb mistakes.
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: 
>>> 
>>> yaron@astro.as.utexas.edu (Yaron Sheffer) writes (referring to the Crab
>>> Nebula pulsar and its radio jets):
>>> 
>>>> after the pulsar flies away and the nebula disperses, NOTHING IS LEFT
>>>> BEHIND! Does Tom see ANY similarity between this scenario and galaxy cores
>>>> that "eject quasars"? As far as I know, the mammoth core is still there
>>>> intact after such imaginary ejection! Or should we wait to see a galactic
>>>> core exploding as a supernova and vanishing?!
>>> 
>>>      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.

>[stuff deleted]

>> 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
^^^^
 II SN
>type Ia may have no dispersion in magnitude (AJ 100, pg 530).  

>> 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
           II SN
>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
          ^^^^^^
           II SN 
>the massive ones. I don't believe that any type IIa SN (at least good
                                                 ^^^^^^
                                                  II SN
>ones, I mean ones that are definitely type IIs). have been observed 
>[stuff deleted]

Note on determination of SN type: The two major types of SN are
determined by their spectra. The type II SN have H and He lines in
their spectra. The type Ia spectra have neither. Their are now 
further types, but these two are the main types. 

When I mentioned good classifications of SN, I was talking about types
identified by their spectra.

>> 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              |

>Jim Buell

Jim Buell
Newsgroups: sci.astro