Star gets torn apart by massive black hole

[AntonL]

although observed about 3 months ago I only learned about it today -I hope it is not a double post

http://chandra.harvard.edu/photo/2011/grb110328/
http://www.universetoday.com/84694/space-telescopes-observe-unprecedented-explosion/

and two arxiv papers:
http://arxiv.org/PS_cache/arxiv/pdf/1104/1104.3257v1.pdf"
and
http://arxiv.org/PS_cache/arxiv/pdf/1104/1104.3356v1.pdf"

should this event not have produced gravity waves? at 3.8 billion light years distance I presume it to be too far to be detected by LIGO

 

[phinds]

I'll bet this IS the kind of thing that produce detectable gravity waves, assuming they exist, and assuming we ever figure out how to get instruments to detect them then we WILL detect them some day (actually, I'm not well read in this area and only vaguely remember reading that we can't already detect them ... could be wrong?)

 

[zhermes]

should this event not have produced gravity waves? at 3.8 billion light years distance I presume it to be too far to be detected by LIGO

This event certainly produced some gravity waves (many things do). The signal would be far too weak for a LIGO like detector to detect at such a distance. Additionally, the frequency the waves would have been created at would be far lower than the LIGO sensitive band---so even if this occurred in our own galaxy, we still wouldn't have been able to detect it.

... assuming we ever figure out how to get instruments to detect them then we WILL detect them some day (actually, I'm not well read in this area and only vaguely remember reading that we can't already detect them ... could be wrong?)

LIGO/Virgo GW detectors have been fully operational at original design specifications. They have yet to make any detections, consistent with our expectations of source strengths and rates.

Currently the LIGO/Virgo network is undergoing upgrades (and are presently off-line) which will significantly increase the chance of making a detection. After the upgrades are complete (~2015), we should see a detection within a few years. If we don't, it might be an important discovery in itself.

 

[marcus]

Excellent discussion, thanks! I think there was something about this ripped apart star in
astrophysics forum, where PAllen had some astute comments about how you calculate how close the star can get to the BH.

Yes it was here:
https://www.physicsforums.com/showthread.php?t=507567
"Star swallowed by galactic black hole".

PAllen had a couple of comments in that thread.

My feeling is that inadvertent doubling does little harm, nobody's fault, I'm glad that BOTH threads were started. They can always be combined later if Mods deem necessary. The main thing is that this is an exciting and rare event.

 

[Nabeshin]

Additionally, the frequency the waves would have been created at would be far lower than the LIGO sensitive band---so even if this occurred in our own galaxy, we still wouldn't have been able to detect it.

Just a note, the frequency would be too low for even the proposed LISA detector, so I think there is no hope in near future of seeing an event like this with gravitational wave detectors.