GRB 970228

Last updated
GRB 970228
GRB 970228.jpg
Event type Gamma-ray burst   OOjs UI icon edit-ltr-progressive.svg
Constellation Orion   OOjs UI icon edit-ltr-progressive.svg
Right ascension 05h 01m 46.7s
Declination +11° 46′ 53.0″ [1]
Epoch J2000
Distance8,123,000,000 ly (2.491×109 pc)
Redshift 0.695, 0.695  OOjs UI icon edit-ltr-progressive.svg
Total energy output5.2×1044  J
Other designationsGRB 970228
  Commons-logo.svg Related media on Commons
[ edit on Wikidata]

GRB 970228 [2] was the first gamma-ray burst (GRB) for which an afterglow was observed. [3] It was detected on 28 February 1997 at 02:58 UTC. Since 1993, physicists had predicted GRBs to be followed by a lower-energy afterglow (in wavelengths such as radio waves, x-rays, and even visible light), but until this event, GRBs had only been observed in highly luminous bursts of high-energy gamma rays (the most energetic form of electromagnetic radiation); this resulted in large positional uncertainties which left their nature very unclear.

Contents

The burst had multiple peaks in its light curve and lasted approximately 80 seconds. Peculiarities in the light curve of GRB 970228 suggested that a supernova may have occurred as well. The position of the burst coincided with a galaxy about 8.1 billion  light-years [4] away (a redshift of z = 0.695), providing early evidence that GRBs occur well beyond the Milky Way; this was proven decisively two months later with a subsequent burst GRB 970508.

Observations

A gamma-ray burst (GRB) is a highly luminous flash of gamma rays, the most energetic form of electromagnetic radiation. GRBs were first detected in 1967 by the Vela satellites, a series of spacecraft designed to detect nuclear explosions. [5]

GRB 970228 [2] was detected on 28 February 1997 at 02:58 UTC by the Gamma-Ray Burst Monitor (GRBM) and one of the Wide Field Cameras (WFCs) on board BeppoSAX, [6] [7] an Italian–Dutch satellite originally designed to study X-rays. [8] The burst lasted around 80 seconds and had multiple peaks in its light curve. [9] Gamma-ray bursts have very diverse time profiles, and it is not fully understood why some bursts have multiple peaks and some have only one. One possible explanation is that multiple peaks are formed when the source of the gamma-ray burst undergoes precession. [10] Within a few hours, the BeppoSAX team used the X-ray detection to determine the burst's position with an error box—a small area around the specific position to account for the error in the position—of 3  arcminutes. [7] The burst was also detected by the Ulysses space probe. [11]

About one and nine days later, optical images of the error box were taken with the William Herschel Telescope on La Palma; comparison of the images revealed a fading point source located at a right ascension of 05h 01m 46.7s and a declination of +11° 46′ 53.0″, providing the first arcsecond-accuracy localization of any Gamma-ray burst. [1]

Later images after the point source faded revealed a faint galaxy at almost the same position, the presumed host galaxy of the burst; a chance position coincidence was unlikely but possible, so the cosmological origin of GRBs was not conclusive until observations of GRB 970508 about two months later.

Afterglow

In 1993, Bohdan Paczyński and James E. Rhoads published an article arguing that, regardless of the type of explosion that causes GRBs, the extreme energetics of GRBs meant that matter from the host body must be ejected at relativistic speeds during the explosion. They predicted that the interaction between the ejecta and interstellar matter would create a shock front. Should this shock front occur in a magnetic field, accelerated electrons in it would emit long-lasting synchrotron radiation in the radio frequencies, a phenomenon that would later be referred to as a radio afterglow. [12] Jonathan Katz later concluded that this lower-energy emission would not be limited to radio waves, but should range in frequency from radio waves to x-rays, including visible light. [13]

The Narrow Field Instruments on board BeppoSAX began making observations of the GRB 970228's position within eight hours of its detection. [9] A transient x-ray source was detected which faded with a power-law slope in the days following the burst. This x-ray afterglow was the first GRB afterglow ever detected. [7] Power-law decays have since been recognized as a common feature in GRB afterglows, although most afterglows decay at differing rates during different phases of their lifetimes. [14]

Optical images were taken of GRB 970228's position on 1 and 8 March using the William Herschel Telescope and the Isaac Newton Telescope. Comparison of the images revealed an object which had decreased in luminosity in both visible light and infrared light. [1] This was the burst's optical afterglow. Deeper follow-up observations using the New Technology Telescope showed that the afterglow coincided with a distant, small galaxy: the first evidence of the extragalactic, cosmological nature of Gamma-ray bursts. [15] [16] After the gamma-ray bursts itself had faded away, very deep observations taken with the Keck telescopes showed the underlying galaxy to have a redshift of 0.695. The predicted radio afterglow was never detected for this burst. [17] At the time of this burst's discovery, GRBs were believed to emit radiation isotropically. The afterglows from this burst and several others—such as GRB 970508 and GRB 971214—provided early evidence that GRBs emit radiation in collimated jets, a characteristic which lowers the total energy output of a burst by several orders of magnitude. [18]

Supernova relation

Artist's illustration showing the life of a massive star as it goes supernova, collapses into a black hole, and emits a gamma-ray burst along its axis of rotation Credit: Nicolle Rager Fuller/NSF Gamma ray burst.jpg
Artist's illustration showing the life of a massive star as it goes supernova, collapses into a black hole, and emits a gamma-ray burst along its axis of rotation Credit: Nicolle Rager Fuller/NSF

Daniel Reichart of the University of Chicago and Titus Galama of the University of Amsterdam independently analyzed GRB 970228's optical light curve, both concluding that the host object may have undergone a supernova explosion several weeks before the gamma-ray burst occurred. [19] [20]

Galama analyzed the light curve of the burst and found that its luminosity decayed at different rates at different times. The luminosity decayed more slowly between March 6 and April 7 than it did before and after these dates. Galama concluded that the earlier light curve had been dominated by the burst itself, whereas the later light curve was produced by the underlying Type Ic supernova. [21] Reichart noted that the late afterglow was redder than the early afterglow, an observation which conflicted with the then-preferred relativistic fireball model for the gamma-ray burst emission mechanism. He also observed that the only GRB with a similar temporal profile was GRB 980326, [20] for which a supernova relation had already been proposed by Joshua Bloom. [22]

An alternative explanation for the light curves of GRB 970228 and GRB 980326 involved dust echoes. Although GRB 980326 did not provide enough information to definitively rule out this explanation, Reichart showed that the light curve of GRB 970228 could only have been caused by a supernova. [23] Definitive evidence linking gamma-ray bursts and supernovae was eventually found in the spectrum of GRB 020813 [24] and the afterglow of GRB 030329. [25] However, supernova-like features only become apparent in the weeks following a burst, leaving the possibility that very early luminosity variations could be explained by dust echoes. [26]

Host galaxy

During the night between 12 and 13 March, Jorge Melnick made observations of the region with the New Technology Telescope. He discovered a faint nebular patch at the burst's position, almost certainly a distant galaxy. Although there was a remote chance that the burst and this galaxy were unrelated, their positional coincidence provided strong evidence that GRBs occur in distant galaxies rather than within the Milky Way. [27] This conclusion was later supported by observations of GRB 970508, the first burst to have its redshift determined. [28]

The position of the burst's afterglow was measurably offset from the centroid of the host galaxy, effectively ruling out the possibility that the burst originated in an active galactic nucleus. The redshift of the galaxy was later determined to be z = 0.695, [17] which corresponds to a distance of approximately 8.123×109  ly . [4] At this distance, the burst would have released a total of 5.2×1044  J assuming isotropic emission. [29]

Notes

  1. 1 2 3 Groot 12 March 1997
  2. 1 2 "GRB" indicates that the event was a gamma-ray burst, and the numbers follow a YYMMDD format corresponding to the date on which the burst occurred: 28 February 1997.
  3. ↑ Schilling 2002, p. 101
  4. 1 2 Converting of the redshift into the distance done by on-line tools:
    Wright, Edward L. (9 May 2008). "Ned Wright's Javascript Cosmology Calculator". UCLA Division of Astronomy & Astrophysics. Retrieved 2010-06-11.
  5. ↑ Schilling 2002, pp. 12–16
  6. ↑ Varendoff 2001, p. 381
  7. 1 2 3 Costa 1997b
  8. ↑ Schilling 2002, pp. 58–60
  9. 1 2 Costa 1997a
  10. ↑ Zwart 2001
  11. ↑ Hurley 1997
  12. ↑ Paczyński 1993
  13. ↑ Katz 1994
  14. ↑ Panaitescu 2007, §2
  15. ↑ Groot 14 March 1997
  16. ↑ Van Paradijs et al., 1997
  17. 1 2 Bloom 2001
  18. ↑ Huang 2002
  19. ↑ Schilling 2002, p. 173
  20. 1 2 Reichart 1999
  21. ↑ Galama 2000
  22. ↑ Bloom 1999
  23. ↑ Reichart 2001
  24. ↑ Butler 2003
  25. ↑ Stanek 2003
  26. ↑ Moran 2005
  27. ↑ Schilling 2002, p. 102
  28. ↑ Reichart 1998
  29. ↑ Djorgovski 1999

Related Research Articles

<span class="mw-page-title-main">Gamma-ray burst</span> Flashes of gamma rays from distant galaxies

In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies, being the brightest and most extreme explosive events in the entire universe, as NASA describes the bursts as the "most powerful class of explosions in the universe". They are the most energetic and luminous electromagnetic events since the Big Bang. Gamma-ray bursts can last from ten milliseconds to several hours. After the initial flash of gamma rays, an "afterglow" is emitted, which is longer lived and usually emitted at longer wavelengths.

<span class="mw-page-title-main">Superluminous supernova</span> Supernova at least ten times more luminous than a standard supernova

A super-luminous supernova is a type of stellar explosion with a luminosity 10 or more times higher than that of standard supernovae. Like supernovae, SLSNe seem to be produced by several mechanisms, which is readily revealed by their light-curves and spectra. There are multiple models for what conditions may produce an SLSN, including core collapse in particularly massive stars, millisecond magnetars, interaction with circumstellar material, or pair-instability supernovae.

GRB 971214 is a gamma-ray burst observed in 1997. It originated 12 billion light years away. For a brief period this was thought by some researchers to have been the most energetic event observed in the universe, but this was before it was established that gamma-ray bursts are beamed towards the Earth. Thus, at the time of the discovery it was hypothesized by G. Djorgovski and his collaborators that the outburst put out more energy than several hundred typical supernovae, or the energy our galaxy puts out over a couple of centuries. However, a couple of years later it was realized that this was an upper limit as it is likely that the burst was directed towards Earth. If the jet had an opening angle of only a few degrees, the burst energy could have been thousands of times lower. The X-ray afterglow and the host galaxy of the GRB have also been observed, using BeppoSAX and Keck II respectively. The host galaxy lies at redshift z=3.4.

<span class="mw-page-title-main">SN 1998bw</span>

SN 1998bw was a rare broad-lined Type Ic gamma ray burst supernova detected on 26 April 1998 in the ESO 184-G82 spiral galaxy, which some astronomers believe may be an example of a collapsar (hypernova). The hypernova has been linked to GRB 980425, which was detected on 25 April 1998, the first time a gamma-ray burst has been linked to a supernova. The hypernova is approximately 140 million light years away, very close for a gamma ray burst source.

Gamma-ray burst emission mechanisms are theories that explain how the energy from a gamma-ray burst progenitor is turned into radiation. These mechanisms are a major topic of research as of 2007. Neither the light curves nor the early-time spectra of GRBs show resemblance to the radiation emitted by any familiar physical process.

<span class="mw-page-title-main">Gamma-ray burst progenitors</span> Types of celestial objects that can emit gamma-ray bursts

Gamma-ray burst progenitors are the types of celestial objects that can emit gamma-ray bursts (GRBs). GRBs show an extraordinary degree of diversity. They can last anywhere from a fraction of a second to many minutes. Bursts could have a single profile or oscillate wildly up and down in intensity, and their spectra are highly variable unlike other objects in space. The near complete lack of observational constraint led to a profusion of theories, including evaporating black holes, magnetic flares on white dwarfs, accretion of matter onto neutron stars, antimatter accretion, supernovae, hypernovae, and rapid extraction of rotational energy from supermassive black holes, among others.

<span class="mw-page-title-main">GRB 080319B</span> Gamma-ray burst in the constellation Boötes

GRB 080319B was a gamma-ray burst (GRB) detected by the Swift satellite at 06:12 UTC on March 19, 2008. The burst set a new record for the farthest object that was observable with the naked eye: it had a peak visual apparent magnitude of 5.7 and remained visible to human eyes for approximately 30 seconds. The magnitude was brighter than 9.0 for approximately 60 seconds. If viewed from 1 AU away, it would have had a peak apparent magnitude of −67.57. It had an absolute magnitude of −38.6, beaten by GRB 220101A with −39.4 in 2023.

<span class="mw-page-title-main">GRB 970508</span> Gamma-ray burst detected on May 8, 1997

GRB 970508 was a gamma-ray burst (GRB) detected on May 8, 1997, at 21:42 UTC; it is historically important as the second GRB with a detected afterglow at other wavelengths, the first to have a direct redshift measurement of the afterglow, and the first to be detected at radio wavelengths.

The history of gamma-ray began with the serendipitous detection of a gamma-ray burst (GRB) on July 2, 1967, by the U.S. Vela satellites. After these satellites detected fifteen other GRBs, Ray Klebesadel of the Los Alamos National Laboratory published the first paper on the subject, Observations of Gamma-Ray Bursts of Cosmic Origin. As more and more research was done on these mysterious events, hundreds of models were developed in an attempt to explain their origins.

<span class="mw-page-title-main">GRB 051221A</span> Gamma ray burst in 2005

GRB 051221A was a gamma ray burst (GRB) that was detected by NASA's Swift Gamma-Ray Burst Mission on December 21, 2005. The coordinates of the burst were α=21h 54m 50.7s, δ=16° 53′ 31.9″, and it lasted about 1.4 seconds. The same satellite discovered X-ray emission from the same object, and the GMOS Instrument on the Gemini Observatory discovered an afterglow in the visible spectrum. This was observed for the next ten days, allowing a redshift of Z = 0.5464 to be determined for the host galaxy.

<span class="mw-page-title-main">GRB 050709</span>

GRB 050709 was a gamma-ray burst (GRB) detected on July 9, 2005. A gamma-ray burst is a highly luminous flash of gamma rays, the most energetic form of electromagnetic radiation, which is often followed by a longer-lived "afterglow" emitting at longer wavelengths.

GRB 020813 was a gamma-ray burst (GRB) that was detected on 13 August 2002 at 02:44 UTC. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths.

GRB 011211 was a gamma-ray burst (GRB) detected on December 11, 2001. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths.

GRB 031203 was a gamma-ray burst (GRB) detected on December 3, 2003. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths.

GRB 030329 was a gamma-ray burst (GRB) that was detected on 29 March 2003 at 11:37 UTC. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths. GRB 030329 was the first burst whose afterglow definitively exhibited characteristics of a supernova, confirming the existence of a relationship between the two phenomena.

GRB 070714B was a gamma-ray burst (GRB) that was detected on 14 July 2007 at 04:59 UTC. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths.

<span class="mw-page-title-main">Tsvi Piran</span> Israeli theoretical physicist and astrophysicist (born 1949)

Tsvi Piran is an Israeli theoretical physicist and astrophysicist, best known for his work on Gamma-ray Bursts (GRBs) and on numerical relativity. The recipient of the 2019 EMET prize award in Physics and Space Research.

<span class="mw-page-title-main">Daniel E. Reichart</span> American astronomer

Daniel E. Reichart is an American astronomer. Reichart’s dissertation research on distant, cosmic explosions called gamma-ray bursts was ranked by Science Magazine as one of the top ten discoveries in science in 1999, and in 2003 earned him the Robert J. Trumpler Award, for top astrophysics dissertation research in North America. In 2005, he and his students discovered the most distant explosion in the universe yet known, a gamma-ray burst that occurred 12.9 billion years ago, when the universe was only 6% its current age.

<span class="mw-page-title-main">Hypernova</span> Supernova that ejects a large mass at unusually high velocity

A hypernova is a very energetic supernova which is believed to result from an extreme core collapse scenario. In this case, a massive star collapses to form a rotating black hole emitting twin astrophysical jets and surrounded by an accretion disk. It is a type of stellar explosion that ejects material with an unusually high kinetic energy, an order of magnitude higher than most supernovae, with a luminosity at least 10 times greater. Hypernovae release such intense gamma rays that they often appear similar to a type Ic supernova, but with unusually broad spectral lines indicating an extremely high expansion velocity. Hypernovae are one of the mechanisms for producing long gamma ray bursts (GRBs), which range from 2 seconds to over a minute in duration. They have also been referred to as superluminous supernovae, though that classification also includes other types of extremely luminous stellar explosions that have different origins.

References

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.