PDA

View Full Version : Discussion: Microquasar Puzzles Astronomers



Fraser
2005-Jul-08, 03:55 PM
SUMMARY: An international team of astronomers have discovered a strange source of high energy gamma rays. The object is called LS5039, and it's known as a microquasar because of the kinds of radiation it generates. Microquasars are binary systems, where a regular star orbits a dead star, like a neutron star or black hole. Material streams from the regular star to the neutron star in such quantity that it starts to back up, like too much water going down a drain. What's unusual about LS5039 is that it's producing more high energy gamma rays than should be possible.

View full article (http://www.universetoday.com/am/publish/compact_object_hess_high_energy.html)

What do you think about this story? Post your comments below.

antoniseb
2005-Jul-08, 05:59 PM
The arXiv paper on this indicated that although we don't know the exact mechanism for these VHE gamma rays, coming from this object, it is likely to be at least in part due to the interactions of the B giant with the collapsed object in terms of magnetic fields. The specifics of how these fields create such things needs a lot of fleshing out.

iantresman
2005-Jul-08, 08:22 PM
Originally posted by fraser@Jul 8 2005, 04:55 PM
What's unusual about LS5039 is that it's producing more high energy gamma rays than should be possible.
It sounds to me that the suggested mechanism is incorrect. Some other peer-reviewed articles have suggested that plasma double layers could be the source, which are known to accelerate ions to relativistics velocities. Fore example: Electrodynamics of disk-accreting magnetic neutron stars (http://articles.adsabs.harvard.edu//full/seri/ApJS./0090//0000833.000.html) (1994) by Miller, M. C., et al
Disk-accreting magnetic neutron stars as high-energy particle accelerators (http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1994ApJS...90..837H) (1994) by Hamilton, R. J., et al
Particle acceleration and nonthermal energy release as an effect of magnetoactive disk accretion onto gravitating center (http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1994ApJS...90..959I) (1994) by Ikhsanov, N. R. & Pustil'nik, L. A.
Creation of Gamma-Ray Burts by Electric Currents and Double Layers (http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998tx19.confE..73O&db_key=AST&link_type=ABSTRACT&high=42ca922c9c01479) (1998) by Opher, E.; Opher, R.
Evolution of the Plasma Universe: I. Double Radio Galaxies, Quasars, and Extragalactic Jets (http://public.lanl.gov/alp/plasma/downloadsCosmo/Peratt86TPS-I.pdf) (1986) (PDF) by A. L. Peratt
Regards,
Ian Tresman

Greg
2005-Jul-09, 04:24 AM
Nice set of articles. Thanks for the post. Looks like this phenomenon was suggested by Compton data and predicted by these authors. So it really isn't much of a surprise to see these systems as sources of infrequent gamma ray bursts. With further study, it should be possible to deduce something about the characteristics of the black holes/neutron stars producing these bursts. I would be most curious to see what effect rotational speed of the dense object has on the quasar jet.

Nick4
2005-Jul-27, 03:03 AM
If a star is dead dose it still have gravity or dose that depend on the mass of whats left of the star?

Nereid
2005-Jul-27, 11:10 PM
Originally posted by Nick4@Jul 27 2005, 03:03 AM
If a star is dead dose it still have gravity or dose that depend on the mass of whats left of the star?
Huh?

A star's gravity is determined by its mass - whether it emitting radio waves, light, or high energy gammas (or not) has no effect on its mass (that would be detectable by any technique we have in the first decade of the 21st century).

Perhaps you had something else in mind?

Joff
2005-Jul-27, 11:22 PM
Originally posted by Nick4@Jul 27 2005, 03:03 AM
If a star is dead dose it still have gravity?
Probably it has more gravity.

After all, being dead is a very grave matter. ;)

Nereid
2005-Jul-28, 11:46 PM
Originally posted by iantresman+Jul 8 2005, 08:22 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (iantresman &#064; Jul 8 2005, 08:22 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-fraser@Jul 8 2005, 04:55 PM
What&#39;s unusual about LS5039 is that it&#39;s producing more high energy gamma rays than should be possible.
It sounds to me that the suggested mechanism is incorrect. Some other peer-reviewed articles have suggested that plasma double layers could be the source, which are known to accelerate ions to relativistics velocities. Fore example:
Electrodynamics of disk-accreting magnetic neutron stars (http://articles.adsabs.harvard.edu//full/seri/ApJS./0090//0000833.000.html) (1994) by Miller, M. C., et al

Disk-accreting magnetic neutron stars as high-energy particle accelerators (http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1994ApJS...90..837H) (1994) by Hamilton, R. J., et al

Particle acceleration and nonthermal energy release as an effect of magnetoactive disk accretion onto gravitating center (http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1994ApJS...90..959I) (1994) by Ikhsanov, N. R. & Pustil&#39;nik, L. A.

Creation of Gamma-Ray Burts by Electric Currents and Double Layers (http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998tx19.confE..73O&db_key=AST&link_type=ABSTRACT&high=42ca922c9c01479) (1998) by Opher, E.; Opher, R.

Evolution of the Plasma Universe: I. Double Radio Galaxies, Quasars, and Extragalactic Jets (http://public.lanl.gov/alp/plasma/downloadsCosmo/Peratt86TPS-I.pdf) (1986) (PDF) by A. L. Peratt

Regards,
Ian Tresman [/b][/quote]
Thanks Ian.

#4 on your list seems to be only an abstract (and about GRBs to boot, not this kind of system), and #5 (the Peratt paper) completely irrelevant - did I miss something?