History of gamma-ray burst research
The history of gamma-ray began with the
Discovery
Gamma-ray bursts were discovered in the late 1960s by the U.S.
On July 2, 1967, at 14:19
Vela 5 was launched on May 23, 1969. Because the sensitivity and time resolution on these satellites were significantly more accurate than the instruments on Vela 4, the Los Alamos team expected these new satellites to detect more gamma-ray bursts. Despite an enormous amount of
Although their instrumentation offered no improvement over those on Vela 5, the Vela 6 satellites were launched on April 8, 1970, with the intention of determining the direction from which the gamma rays were arriving. The orbits for the Vela 6 satellites were chosen to be as far away from Vela 5 as possible, generally on the order of 10000 kilometers apart. This separation meant that, despite gamma rays traveling at the speed of light, a signal would be detected at slightly different times by different satellites. By analyzing the arrival times, Klebesadel and his team successfully traced sixteen gamma-ray bursts. The random distribution of bursts across the sky made it clear that the bursts were not coming from the sun, moon, or other planets in our solar system.[3]
In 1973, Ray Klebesadel, Roy Olson, and Ian Strong of the
Early research missions
Shortly after the discovery of gamma-ray bursts, a general consensus arose within the astronomical community that in order to determine what caused them, they would have to be identified with astronomical objects at other wavelengths, particularly visible light, as this approach had been successfully applied to the fields of radio X-ray astronomy. This method would require far more accurate positions of several gamma-ray bursts than the Vela system could provide.[6] Greater accuracy required the detectors to be spaced farther apart. Instead of launching satellites only into Earth's orbit, it was deemed necessary to spread the detectors throughout the solar system.
By the end of 1978, the first Inter-Planetary Network (
To explain the existence of gamma-ray bursts, many speculative theories were advanced, most of which posited nearby
BATSE data also showed that GRBs fall into two distinct categories: short-duration, hard-spectrum bursts ("short bursts"), and long-duration, soft-spectrum bursts ("long bursts").[11] Short bursts are typically less than two seconds in duration and are dominated by higher-energy photons; long bursts are typically more than two seconds in duration and dominated by lower-energy photons. The separation is not absolute and the populations overlap observationally, but the distinction suggests two different classes of progenitors. However, some believe there is a third type of GRBs.[12][13][14][15] The three kinds of GRBs are hypothesized to reflect three different origins: mergers of neutron star systems, mergers between white dwarfs and neutron stars, and the collapse of massive stars.[16]
For decades after the discovery of GRBs, astronomers searched for a counterpart: any astronomical object in positional coincidence with a recently observed burst. Astronomers considered many distinct objects, including
As early as 1980, a research group headed by
In 1983, a team composed of
Observations and analysis
BeppoSAX detected its first gamma-ray burst GRB960720 on July 20, 1996
Success for the BeppoSAX team came in February 1997, less than one year after it had been launched. A BeppoSAX WFC detected a gamma-ray burst (GRB 970228), and when the X-ray camera onboard BeppoSAX was pointed towards the direction from which the burst had originated, it detected a fading X-ray emission. Ground-based telescopes later identified a fading optical counterpart as well.[32] The location of this event having been identified, once the GRB faded, deep imaging was able to identify a faint, very distant host galaxy in the GRB's location. Within only a few weeks the long controversy about the distance scale ended: GRBs were extragalactic events originating inside faint galaxies at enormous distances.[nb 2] By finally establishing the distance scale, characterizing the environments in which GRBs occur, and providing a new window on GRBs both observationally and theoretically, this discovery revolutionized the study of GRBs.[33]
Two major breakthroughs also occurred with the next event registered by BeppoSAX,
Prior to the localization of GRB 970228, opinions differed as to whether or not GRBs would emit detectable radio waves.
Also, because GRB 970508 was observed at many different wavelengths, it was possible to form a very complete spectrum for the event. Ralph Wijers and Titus Galama attempted to calculate various physical properties of the burst, including the total amount of energy in the burst and the density of the surrounding medium. Using an extensive system of equations, they were able to compute these values as 3×1052 ergs and 30,000 particles per cubic meter, respectively. Although the observation data was not accurate enough for their results to be considered particularly reliable, Wijers and Galama did show that, in principle, it would be possible to determine the physical characters of GRBs based on their spectra.[37]
The next burst to have its redshift calculated was GRB 971214 with a redshift of 3.42, a distance of roughly 12 billion lightyears from Earth. Using the redshift and the accurate brightness measurements made by both BATSE and BeppoSAX, Shrinivas Kulkarni, who had recorded the redshift at the W. M. Keck Observatory, calculated the amount of energy released by the burst in half a minute to be 3×1053 ergs, several hundred times more energy than is released by the Sun in 10 billion years. The burst was proclaimed to be the most energetic explosion to have ever occurred since the Big Bang, earning it the nickname Big Bang 2. This explosion presented a dilemma for GRB theoreticians: either this burst produced more energy than could possibly be explained by any of the existing models, or the burst did not emit energy in all directions, but instead in very narrow beams which happened to have been pointing directly at Earth. While the beaming explanation would reduce the total energy output to a very small fraction of Kulkarni's calculation, it also implies that for every burst observed on Earth, several hundred occur which are not observed because their beams are not pointed towards Earth.[38]
In November 2019, astronomers reported a notable
Current missions
INTEGRAL, the European Space Agency's International Gamma-Ray Astrophysics Laboratory, was launched on October 17, 2002. It is the first observatory capable simultaneously observing objects at gamma ray, X-ray, and visible wavelengths.[42]
On June 11, 2008 NASA's Gamma-ray Large Area Space Telescope (GLAST), later renamed the Fermi Gamma-ray Space Telescope, was launched. The mission objectives include "crack[ing] the mysteries of the stupendously powerful explosions known as gamma-ray bursts."[44]
Another gamma-ray burst observation mission is
Notes
- ^ GRBs are named after the date on which they are discovered: the first two digits being the year, followed by the two-digit month and two-digit day, then a letter corresponding to the order upon which it was detected (A for first of that day, B for second, and so on). Before 2010 this was only signified if two or more GRBs were detected on a given day.
- ^ For more on galaxies hosting GRBs, see the GHostS database http://www.grbhosts.org
References
- ^ doi:10.1086/181225.
- ^ a b Katz 2002, p. 4–5
- ^ a b c d Schilling 2002, p.12–16
- ^ Schilling 2002, p.16–17
- ^ Hurley 2003
- ^ Katz 2002, p. 19
- ^ Schilling 2002, p. 19–20
- ^ Meegan 1992
- ^ Schilling 2002, p.36–37
- ^ Paczyński 1999, p. 6
- ^ Kouveliotou 1993
- ^ Mukherjee 1998
- ^ Horvath 1998
- ^ Hakkila 2003
- ^ Horvath 2006
- ^ Chattopadhyay 2007
- ^ a b Liang 1986, p. 33
- ^ Liang 1986, p. 39
- ^ Schilling 2002, p. 20
- ^ Fishman 1995
- ^ Schilling 2002, p. 58–60
- ^ Schilling 2002, p. 63
- ^ Schilling 2002, p. 65
- ^ Schilling 2002, p. 67
- ^ a b Schilling 2002, p. 62–63
- ^ Schilling 2002, p. 56
- ^ Schilling 2002, p. 69–70
- ^ Schilling 2002, p. 252–253
- ^ IAUC 6467 (International Astronomical Union Circular) by Piro et al., 3 September 1996, see also circulars 6472 (Frail et al.), 6480 (Piro et al.), 6569 (in 't Zand et al.), 6570 (Greiner et al.)
- ^ a b Schilling 2002, p. 86–89
- ^ Schilling 2002, p. 84
- ^ van Paradijs 1997
- ^ Frontera 1998
- ^ Schilling 2002, p. 118–123
- ^ Schilling 2002, p. 114–115
- ^ Schilling 2002, p. 124–126
- ^ Schilling 2002, p. 141–142
- ^ Schilling 2002, p. 150–153
- EurekAlert!(Press release). Retrieved 20 November 2019.
- S2CID 208191199.
- ^ Aptekar 1995
- ESA. 2011-03-15. Retrieved 2011-11-23.
- ^ Gehrels 2004
- ^ "Official NASA Fermi Website". fermi.gsfc.nasa.gov. Retrieved 2008-12-05.
Bibliography
- Chattopadhyay, T.; et al. (2007). "Statistical Evidence for Three Classes of Gamma-Ray Bursts". Astrophysical Journal. 667 (2): 1017–1023. S2CID 14923248.
- Fishman, C. J.; Meegan, C. A. (1995). "Gamma-Ray Bursts". Annual Review of Astronomy and Astrophysics. 33 (1): 415 458. .
- Frontera, F.; Piro, L. (1998). Proceedings of Gamma-Ray Bursts in the Afterglow Era. Astronomy and Astrophysics Supplement Series. Archived from the original on 2006-08-08.
- Gehrels, N.; et al. (2004). "The Swift Gamma-Ray Burst Mission". Astrophysical Journal. 611 (2): 1005–1020. S2CID 17871491.
- Hakkila, J.; et al. (2003). "How Sample Completeness Affects Gamma-Ray Burst Classification". Astrophysical Journal. 582 (1): 320–329. S2CID 14606496.
- Horvath, I. (1998). "A Third Class of Gamma-Ray Bursts?". Astrophysical Journal. 508 (2): 757–759. S2CID 119395213.
- Horvath, I.; et al. (2006). "A new definition of the intermediate group of gamma-ray bursts". Astronomy and Astrophysics. 447 (1): 23–30. S2CID 15216537.
- Hurley, K. (2003). "A Gamma-Ray Burst Bibliography, 1973-2001" (PDF). In G. R. Ricker; R. K. Vanderspek (eds.). Gamma-Ray Burst and Afterglow Astronomy, 2001: A Workshop Celebrating the First Year of the HETE Mission. ISBN 0-7354-0122-5. Retrieved 2009-03-12.
- Katz, Johnathan I. (2002). The Biggest Bangs. Oxford University Press. ISBN 0-19-514570-4.
- Klebesadel, R.; et al. (1973). "Observations of Gamma-Ray Bursts of Cosmic Origin". Astrophysical Journal. 182: L85. doi:10.1086/181225.
- Kouveliotou, C.; et al. (1993). "Identification of two classes of gamma-ray bursts". Astrophysical Journal. 413: L101. doi:10.1086/186969.
- Liang, Edison P.; Vahé Petrosian, eds. (1986). AIP Conference Proceedings No. 141. New York: American Institute of Physics. ISBN 0-88318-340-4.
- Meegan, C. A.; et al. (1992). "Spatial distribution of gamma-ray bursts observed by BATSE". Nature. 355 (6356): 143–145. S2CID 4301714.
- Mukherjee, S.; et al. (1998). "Three Types of Gamma-Ray Bursts". Astrophysical Journal. 508 (1): 314–327. S2CID 17983432.
- Paczyński, Bohdan (1999). "Gamma-Ray Burst–Supernova relation". In M. Livio; N. Panagia; K. Sahu (eds.). Supernovae and Gamma-Ray Bursts: The Greatest Explosions Since the Big Bang. ISBN 0-521-79141-3.
- Schilling, Govert (2002). Flash! The hunt for the biggest explosions in the universe. Cambridge: Cambridge University Press. ISBN 0-521-80053-6.
- van Paradijs, J.; et al. (1997). "Transient optical emission from the error box of the gamma-ray burst of 28 February 1997" (PDF). Nature. 386 (6626): 686–689. S2CID 4248753.
- Aptekar, R.; et al. (1995). "Konus-W gamma-ray burst experiment for the GSS Wind spacecraft". Space Science Reviews. 71 (1–4): 265–272. S2CID 121420345.