What we know about gamma-ray bursts is dwarfed by what we don’t, but chipping away at the problem is getting us places, particularly with the help of amateur astronomers. Thus the news that Finnish amateur Arto Oksanen had found the optical afterglow of GRB 071010B, a gamma-ray burst detected by NASA’s Swift satellite. Oksanen did his work with a 40-centimeter telescope at the Hankasalmi Observatory in Finland.
This is the kind of discovery that would have been all but impossible until recently, relying as it does not only on the Swift satellite’s detection capabilities but also on immediate notification of Earth-based observers over the Internet. Remember: Gamma-ray bursts last anywhere from a few milliseconds to a few hundred seconds, and even though they seem to occur once a day, aligning the Swift data with an optical afterglow means looking just as soon as the notification comes in.
Is luck involved? You would think so, and Oksanen agrees:
…you have to be very lucky (and others have to be unlucky) to discover a GRB afterglow nowadays. The sky location of this GRB was a big advantage for me as I was able to observe this one right from the alert being able to ‘look over the North pole’. And this was a bright afterglow and also the weather was good (just after two weeks of cloudy nights).
Hard work pays off, I have been hoping and trying to do this since 1997 when I got interested about GRBs. Indeed “at last!”.
Image: The afterglow of GRB 071010B. Credit: A. Oksanen/AAVSO.
As far as what GRBs are, the question remains unsettled, although GRB 071010B looks to have been a collapsing, supermassive star whose supernova explosion has resulted in a black hole. With Oksanen’s data in hand, the Gemini and Keck telescopes in Hawaii were able to measure the object’s properties, finding a redshift measurement consistent with a distance of at least seven billion light years. Thus the Finn becomes the first amateur to bag a GRB afterglow since 2003, when South African observer ‘Berto’ Monard pulled it off. More information can be found in this news release from the American Association of Variable Star Observers, which coordinates work between amateurs and professionals.
Meanwhile, I’m thinking about Timothy Ferris’ Seeing In the Dark special on PBS (with excellent accompanying site). The book was terrific, but it was fascinating to actually see the assembly of a remote amateur instrument at the New Mexico Skies site, and to watch Ferris handling the incoming image over the Net. When I think about my own tree-obstructed skies, the idea of using the Net to manipulate a remote telescope gets more enticing with every passing day.
Hi Paul
There’s a lot of theories about what GRBs are – stellar collisions, super-massive stars, compact object mergers, etc etc. The task at the moment is distinguishing the options observationally. Hard to be sure when they’re so far, far away.
Congratulations to Arto!
In addition to his GRB work, Arto has also obtained many observations of transiting extrasolar planets. He was a member of the team that on Sept. 19, 2000, produced an HD 209458b light curve that was the first-ever amateur detection of an extrasolar planet.
I recieved a terse email back in 2001 in response to a letter I wrote to the editor of Scientific American magazine about GRBs. I suggested someone do a comparison with current data on nuclear detonations, wondering if these were merely extraterrestrial mutually assured destructions happening around us. (remember the Drake equation?) I was carefully assured by the editor that the energies involved with a GRB are much larger by many factors of thousands than any simple nuclear bomb.
Still, I would love to compare the data since I do not believe there is any theoretical upper limit on how large a runaway nuclear reaction could be achieved. Anybody checked the data?
Hi Jeff
Runaway nuclear explosions occur in white dwarf stars when they explode as Type 1a supernova after accreting too much mass – i.e. a definite size limit. There are no nuclear reaction mass bigger, aside from the endothermic nuclear reactions in imploding Type II supernovae – that’s energy being absorbed and not radiated. Type II supernova get their energy from gravitational collapse and release a lot of it as neutrinos.
The total energy release in such detonations is more in pure mass energy than the Earth’s mass (in fact more mass than all the planets except Jupiter) – unlikely to be used in a nuclear exchange.
The SN 1987A Link to Others and Gamma-Ray Bursts
Authors: John Middleditch
(Submitted on 16 Aug 2007 (v1), last revised 20 Nov 2007 (this version, v5))
Abstract: Early measurements of SN 1987A can be interpreted in light of a beam/jet (BJ), with a collimation factor greater than 10,000, which impacted polar ejecta (PE) to produce the “Mystery Spot” (MS), ~24 lt-d away. Other details of SN 1987A suggest that it came from a merger of 2 stellar cores of a common envelope (CE) binary, i.e. a “double degenerate” (DD) SN. Even having to penetrate the CE, the BJ may have caused a long-soft (l)GRB upon hitting the PE, thus DD can produce lGRBs. Because DD must be the dominant merger/SN mechanism in elliptical galaxies (EGs), where only short, hard GRBs (sGRBs) have been observed, DD without CE or PE must also produce sGRBs, and thus NS-NS mergers may not make GRBs as we know them, and/or be as common as previously thought. Millisecond pulsars (MSPs) in the non-core-collapsed globular clusters are also 99% DD-formed from WD-WD merger, consistent with their 2.10 ms minimum spin period, the 2.14 ms signal seen from SN 1987A, and sGRBs offset from the centers of EGs. The details of Ia’s suggest that these are also DD, and the total thermonuclear disruption paradigm is now in serious doubt as well, a cause for concern in Ia Cosmology, because Ia’s will appear to be Ic’s when viewed from their DD merger poles, given sufficient matter above that lost to core-collapse.
As a DD SN, 1987A appears to be the Rosetta Stone for 99% of SNe, GRBs and MSPs, including all recent nearby SNe except SN 1986J, and the more distant SN 2006gy. There is no need to invent exotica, such as “collapsars,” to account for GRBs.
Comments: 13 pages, 2 figures, will be shortened and submitted to ApJ Letters. V3, fixed refereces, footnote 3 “There are four …” V4, collimation factor greater than 10^4, fastest particles greater than 0.9c, 24 light-days PBF — a needed candidate for the r-process. V5 “far side (southern)” “greater than 0.9 c” “shows how” “Mystery Spot” To ApJ Letters
Subjects: Astrophysics (astro-ph)
Report number: LA-UR-06-5685
Cite as: arXiv:0708.2263v5 [astro-ph]
Submission history
From: John Middleditch [view email]
[v1] Thu, 16 Aug 2007 18:19:45 GMT (44kb)
[v2] Sun, 26 Aug 2007 05:23:12 GMT (44kb)
[v3] Mon, 17 Sep 2007 21:35:57 GMT (44kb)
[v4] Tue, 13 Nov 2007 20:34:49 GMT (44kb)
[v5] Tue, 20 Nov 2007 22:12:15 GMT (25kb)
http://arxiv.org/abs/0708.2263
A celestial gamma-ray foreground due to the albedo of small solar system bodies and a remote probe of the interstellar cosmic ray spectrum
Authors: Igor V. Moskalenko (Stanford), Troy A. Porter (UCSC), Seth W. Digel (SLAC), Peter F. Michelson (Stanford), Jonathan F. Ormes (DU)
(Submitted on 12 Dec 2007)
Abstract: We calculate the gamma-ray albedo flux from cosmic-ray (CR) interactions with the solid rock and ice in Main Belt asteroids and Kuiper Belt objects (KBOs) using the Moon as a template. We show that the gamma-ray albedo for the Main Belt and Kuiper Belt strongly depends on the small-body mass spectrum of each system and may be detectable by the forthcoming Gamma Ray Large Area Space Telescope (GLAST). The orbits of the Main Belt asteroids and KBOs are distributed near the ecliptic, which passes through the Galactic center and high Galactic latitudes. If detected, the gamma-ray emission by the Main Belt and Kuiper Belt has to be taken into account when analyzing weak gamma-ray sources close to the ecliptic, especially near the Galactic center and for signals at high Galactic latitudes, such as the extragalactic gamma-ray emission. Additionally, it can be used to probe the spectrum of CR nuclei at close-to-interstellar conditions, and the mass spectrum of small bodies in the Main Belt and Kuiper Belt. The asteroid albedo spectrum also exhibits a 511 keV line due to secondary positrons annihilating in the rock. This may be an important and previously unrecognized celestial foreground for the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the Galactic 511 keV line emission including the direction of the Galactic center.
Comments: 8 pages, 5 figures, emulateapj.cls; submitted to ApJ
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0712.2015v1 [astro-ph]
Submission history
From: Igor Moskalenko [view email]
[v1] Wed, 12 Dec 2007 19:17:22 GMT (44kb)
http://arxiv.org/abs/0712.2015
AAVSO Alert Notice 372
Possible naked-eye gamma ray burst detected (GRB 080319B)
March 19, 2008
The intense gamma-ray burst GRB 080319B was detected in
gamma ray, x-ray, optical light, and early indications by two
automated cameras suggest that the optical afterglow of the
burst may have briefly reached naked-eye visibility (mag ~
5.76, GCN 7445, Cwiok et al) within 60 seconds of the onset.
It is highly unlikely the burst was caught visually, but it is
possible the burst may have been detected if any observers
were monitoring this area of the sky (e.g. for minor planet
searching).
The coordinates of the burst are:
RA: 14 31 40.98 , Dec: +36 18 8.8 (J2000)
Observers with any images of this field taken since 2008
March 19 0600 UT are urgently asked to check these images
for optical transients. This includes wide-field images, sky
and meteor patrol images, and any and all CCD imaging,
filtered or not.
Observers are also asked to obtain additional images of
this field as the afterglow decays. The object was at magnitude
16 less than ten hours post burst, but it may remain within
range of observers with 12-inch or larger telescope apertures
and CCD cameras.
If you are able to obtain any magnitudes, magnitude estimates,
or limits from your images, please submit them to the AAVSO
with the name “GRB 080319B” or AUID “000-BFT-137”.
This AAVSO Alert Notice was prepared by Matthew Templeton.
——————————————-
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