编辑“︁GRB 970228”︁

{{Good article}}
{{noteTA
|G1=Astronomy
|G2=Physica
}}
{{Infobox astronomical event
| name = GRB 970228
| image = [[File:GRB 970228.jpg|200px|alt=A black background covered with orange stuff, with a bright orange spot in the upper-left corner and a dimmer orange spot in the center.]]
| caption = [[哈勃太空望远镜]]拍摄的GRB 970228
| credit =
| discovery = 1997年2月28日 <br> 02:58 [[UTC]]
| detected_by = [[BeppoSAX卫星|BeppoSAX]]
| duration = 80秒
| ra = {{RA|05|01|46.7}}
| dec = {{DEC|+11|46|53.0}}<ref name="Groot">[[#GrootCirc|Groot 1997]]</ref>
| epoch = J2000
| redshift = 0.695<ref name="Bloom">[[#Bloom|Bloom 2001]]</ref>（寄主星系）
| distance = 8.123{{e|9}}&nbsp;[[光年]]<ref name=nwjcc>使用以下在线换算系统计算的[[共动距离]]：{{cite web | first=Edward L. | last=Wright | date=2008-05-09 | title=Ned Wright's Javascript Cosmology Calculator | publisher=UCLA Division of Astronomy & Astrophysics | url=http://www.astro.ucla.edu/~wright/CosmoCalc.html | accessdate=2010-06-11 | language=en | archive-date=2018-09-29 | archive-url=https://web.archive.org/web/20180929102855/http://www.astro.ucla.edu/~wright/CosmoCalc.html | dead-url=no }}</ref>
| host =
| constellation = [[猎户座]]
| appmag_v =
| energy = {{val|5.2|e=44|ul=J}}
| names =
}}
'''GRB 970228'''<ref name="nomenclature">“GRB”表示这一天文事件是伽玛射线暴，数字（YYMMDD）表示发生于1997年2月28日。</ref>是天文学家第一个观测到[[余辉 (伽玛射线暴)|余辉]]的[[伽玛射线暴]]。<ref>[[#Schilling|Schilling 2002]], p. 101</ref>这次爆发持续了大约80秒，其[[光变曲线]]有多个极大值。它的光变曲线特性表明可能同时发生了一次[[超新星]]爆发。本次爆发的位置与一个81亿[[光年]]<ref name=nwjcc/>外的星系相符（[[红移]]值z&nbsp;=&nbsp;0.695），说明GRB 970228离[[银河系]]十分远。

自从1993年起，物理学家推测伽玛射线暴之后会产生低能量的余辉（波长为[[无线电波]]、[[X射线]]，甚至是[[可见光]]）。但直到天文学家在1997年2月28日2时58分（[[UTC]]）观测到GRB 970228前，天文学家只观测到高光度高能量的伽玛射线暴（[[电磁波]]中能量最高的部分）。

== 观测 ==
伽玛射线暴是指高[[光度]]的[[伽玛射线]]爆发。伽玛射线暴最早由美国负责侦查苏联和中国[[核试验]]的[[船帆座卫星]]于1967年发现。<ref>[[#Schilling|Schilling 2002]], pp. 12–16</ref>

1997年2月28日2时58分（UTC），[[费米伽玛射线空间望远镜]]和[[BeppoSAX卫星]]上搭载的一台广域照相机<ref>[[#Varendoff|Varendoff 2001]], p. 381</ref><ref name="CostaJournal">[[#CostaJournal|Costa 1997b]]</ref>观测到GRB 970228，<ref name="nomenclature"/>其中后者是德意联合研制的研究X射线的卫星。<ref>[[#Schilling|Schilling 2002]], pp. 58–60</ref>在几小时内，BeppoSAX团队确认了这次伽玛射线暴的位置，测量[[误差]]约为3角分，他们借此框定了所在天区的范围。<ref name="CostaJournal"/>[[尤利西斯号]]探测器也观测到了本次伽玛射线暴。<ref>[[#Hurley|Hurley 1997]]</ref>

这次伽玛暴位于[[赤经]]{{RA|05|01|46.7}}，[[赤纬]]{{DEC|+11|46|53.0}}，<ref name="Groot"/>爆发持续了大约80秒，在光变曲线有多个极大值。<ref name="Costa 1997a">[[#CostaCirc|Costa 1997a]]</ref>伽玛射线暴的光变曲线变化多端，科学家至今也不清楚有多个峰值的原因。一种可能的解释是多个峰值是伽玛射线源经历[[进动]]时产生的。<ref>[[#Zwart|Zwart 2001]]</ref>

== 余辉 ==
1993年，[[玻丹·帕琴斯基]]和詹姆斯·E·罗兹发表论文称，無论伽玛射线暴的产生原因是什么，伽玛暴极强的能量意味着寄主天体在爆发期间必须以[[相对论速度]]（接近光速）喷射出大量物质。它们推测喷出物和[[星际物质]]的强烈作用会形成[[激波波前]]。如果激波波前形成于磁场中，加速的电子会长时间产生无线电频率的[[同步辐射]]，即下文所说的无线电余辉。<ref>[[#Pac|Paczyński 1993]]</ref>乔纳森·卡茨之后总结说，这种低能量的发射不限于无线电波，频率可从无线电波到[[X射线]]，其中还包括[[可见光]]。<ref>[[#Katz|Katz 1994]]</ref>

BeppoSAX卫星上的小视野相机在发现8小时之后开始观测它的所在位置。<ref name="Costa 1997a"/>一个X射线源短暂出现，并在之后几天按[[幂定律]]迅速衰减，直至消失。这次X射线[[余辉 (伽玛射线暴)|余辉]]是首次观测到的伽玛射线暴余辉。<ref name="CostaJournal"/>幂定律衰减从此被认为是伽玛射线暴余辉的普遍特征，尽管多数余辉在不同阶段以不同的速率衰减。<ref>[[#Panaitescu|Panaitescu 2007]], §2</ref>

同年3月1日和8日，天文学家用[[威廉·赫歇耳望远镜]]和[[艾萨克·牛顿望远镜]]拍摄了它所在位置的光学影像。通过比较照片，其光度在[[可见光]]和[[红外光]]波段都下降了，<ref name="Groot">[[#GrootCirc|Groot 1997]]</ref>这就是该伽玛射线暴的光学余辉，而天文学家一直没能观测到预测会发生的无线电余辉。<ref name="Bloom"/>这次伽玛射线暴发现之后，人们开始相信伽玛暴的辐射具有[[各向同性]]。这次伽玛暴和其他几次伽玛暴（例如[[GRB 970508]]和[[GRB 971214]]）一起为伽玛暴以[[平行光|平行]]射流释放辐射提供了早期证据。这使得伽玛暴的总能量输出的估计值降低了几个[[数量级]]。<ref>[[#Huang|Huang 2002]]</ref>

== 与超新星的关系 ==
[[File:Gamma ray burst.jpg|thumb|right|艺术家对于[[恒星#大質量恆星|大质量恒星]]的一生的想象：发生超新星爆发、坍缩成黑洞，并沿着自转轴发生伽玛射线暴。（来自: 尼科尔·拉格·富勒/[[美国国家科学基金会|NSF]]）|alt=从左上到右边，一个蓝色的球不断膨胀并形成更多的层。在最右边，这个球发生了爆炸。从右下方到左边，爆炸过后的球变平成为星周盘，两道亮光从自转轴射出。]]
[[芝加哥大学]]的[[丹尼尔·赖卡特]]和[[阿姆斯特丹大学]]的[[提图斯·加拉玛]]各自分析了GRB 970228的光学光变曲线，都总结出寄主天体可能在伽玛射线暴发生前几周发生了一次[[超新星]]爆发。<ref>[[#Schilling|Schilling 2002]], p. 173</ref><ref name="Reichart99">[[#Reichart99|Reichart 1999]]</ref>

加拉玛分析了本次伽玛射线暴的光变曲线后发现它的光度在不同时间以不同速率衰减。光度在3月6日至4月7日之间衰减得比之前和之后都慢。加拉玛总结道，早期光变曲线主要受伽玛射线暴源的影响，而后期则是由隐藏在背后的[[Ic型超新星]]提供能量。<ref>[[#Galama|Galama 2000]]</ref>赖卡特注意到后期余辉比早期余辉[[光學頻譜|偏红]]（波长增加），这与当时伽玛射线暴形成机理首选的相对性火球模型不相符。他同时观测到只有[[GRB 980326]]这一伽玛射线暴与本次的衰减规律类似，<ref name="Reichart99"/>而[[乔舒亚·布卢姆]]已提出那个伽玛射线暴与超新星有关。<ref>[[#Bloom99|Bloom 1999]]</ref>

另一种关于GRB 970228和GRB 980326光变曲线的解释涉及了[[回光|尘埃回光]]。尽管对于GRB 980236而言并没有足够的訊息来否定这种解释，赖卡特表示GRB 970228光变曲线的变化只可能是超新星造成的。<ref>[[#Reichart01|Reichart 2001]]</ref>将伽玛射线暴与超新星联系起来的决定性证据最终在[[GRB 020813]]的光谱<ref>[[#Butler|Butler 2003]]</ref>和[[GRB 030329]]的余辉中发现。<ref>[[#Stanek|Stanek 2003]]</ref>然而，类似于超新星的特点只有在爆发后几周内可见，这表明早期的光度变化可以用尘埃回光来解释。<ref>[[#Moran|Moran 2005]]</ref>

== 寄主星系 ==
在3月12日和13日的夜晚，[[乔治·梅尔尼克]]用[[新技术望远镜]]观测了该天区。他发现一个暗淡的[[星云]]出现在爆发的位置上，几乎可以确定是一个遥远的星系。尽管伽玛射线暴很小可能与那星系无关，它们位置的出奇相符为上述想法提供了有力证据，即伽玛射线暴来自遥远的星系，不在[[银河系]]當中。<ref>[[#Schilling|Schilling 2002]], p. 102</ref>后来对[[GRB 970508]]的观测证实了这个结论，那也是首次能确定[[红移]]值的伽玛射线暴。<ref>[[#Reichart98|Reichart 1998]]</ref>

本次伽玛暴的余辉在测定误差范围之内处于寄主星系的[[几何中心]]，有力地排除伽玛暴产生于[[活动星系核]]的可能。之后测得这个星系的红移值z&nbsp;=&nbsp;0.695，<ref name="Bloom">[[#Bloom|Bloom 2001]]</ref>约等如{{val|8.123|e=9|ul=光年}}的距离。<ref name=nwjcc />在这样的距离和假设[[各向同性]]的基础上，这次伽玛暴共释放出{{val|5.2|e=44|ul=焦耳}}的能量。<ref>[[#Djorgovski|Djorgovski 1999]]</ref>

== 注释 ==
{{reflist|3}}

== 参考文献 ==
{{refbegin|2}}
* {{en}}{{cite journal | author = Bloom, J. S. ''et al''. | title =  The redshift and the ordinary host galaxy of GRB 970228 | url = https://archive.org/details/sim_astrophysical-journal_2001-06-20_554_2/page/678 | journal = Astrophysical Journal | volume = 554 | issue = 2 | year = 2001 | pages = 678–683 | arxiv = astro-ph/0007244 | doi = 10.1086/321398 | ref = Bloom | bibcode=2001ApJ...554..678B}}
* {{en}}{{cite journal | author = Bloom, J. S. ''et al''. | title = The unusual afterglow of the γ-ray burst of 26 March 1998 as evidence for a supernova connection | journal = Nature | volume = 401 | issue = 6752 | pages = 453–456 | doi = 10.1038/46744 | date = 1999-09-30 |arxiv=astro-ph/9905301 | ref = Bloom99|bibcode = 1999Natur.401..453B }}
* {{en}}{{cite journal | title = The X-ray Afterglows of GRB 020813 and GRB 021004 with Chandra HETGS: Possible Evidence for a Supernova prior to GRB 020813 | journal = The Astrophysical Journal | volume = 597 | issue = 2 | pages = 1010–1016 | date = 2003-11-10 | author = Butler, Nathaniel R. ''et al''. | url = http://iopscience.iop.org/0004-637X/597/2/1010/pdf/0004-637X_597_2_1010.pdf | ref = Butler | doi = 10.1086/378511 | bibcode=2003ApJ...597.1010B|arxiv = astro-ph/0303539 }}
* <cite id = CostaCirc>{{en}}Costa, E. ''et al''. (1997a) "[http://www.cbat.eps.harvard.edu/iauc/06500/06572.html IAU Circular 6572: GRB 970228; 1997aa]{{Wayback|url=http://www.cbat.eps.harvard.edu/iauc/06500/06572.html |date=20120319010159 }}". ''International Astronomical Union''.</cite>
* {{en}}{{cite journal | author = Costa, E. ''et al''. | title = Discovery of an X-ray afterglow associated with the γ-ray burst of 28 February 1997 | journal = Nature | volume = 387 | issue = 6635 | pages = 783–785 | date = 1997b | url = http://www.nature.com/nature/journal/v387/n6635/full/387783a0.html | accessdate = 2009-04-02 | doi = 10.1038/42885 | ref = CostaJournal | arxiv = astro-ph/9706065 | bibcode = 1997Natur.387..783C | archive-date = 2011-05-25 | archive-url = https://web.archive.org/web/20110525190341/http://www.nature.com/nature/journal/v387/n6635/full/387783a0.html | dead-url = no }}
* {{en}}{{cite journal | title = GRB 970228: Redshift and properties of the host galaxy | author = Djorgovski, George | journal = GCN Circulars | volume = 289 | date = 1999-05-03 | url = http://gcn.gsfc.nasa.gov/gcn3/289.gcn3 | ref = Djorgovski | access-date = 2012-01-27 | archive-date = 2009-08-31 | archive-url = https://web.archive.org/web/20090831154755/http://gcn.gsfc.nasa.gov/gcn3/289.gcn3 | dead-url = no }}
* {{en}}{{cite journal | author=Esin, A. A. and Blandford, R. | title=Dust Echoes from Gamma-Ray Bursts | journal=[[Astrophysical Journal]] | volume=534 | issue=2 | year=2000 | pages=L151–L154 | pmid=10813670 | doi=10.1086/312670 | ref = Esin | bibcode=2000ApJ...534L.151E|arxiv = astro-ph/0003415 }}
* <cite id = Fox>{{en}}Fox, D. W. ''et al''. (6 May 1997) "[http://www.cbat.eps.harvard.edu/iauc/06600/06643.html IAU Circular 6643: GRB 970228; 1997by]{{Wayback|url=http://www.cbat.eps.harvard.edu/iauc/06600/06643.html |date=20120318225437 }}". ''International Astronomical Union''.</cite>
* {{en}}{{cite journal | author = Galama, T. J. ''et al''. | title = Evidence for a Supernova in Reanalyzed Optical and Near-Infrared Images of GRB 970228 | journal = The Astrophysical Journal | volume = 536 | issue = 1 | pages = 185–194 | date = 2000-06-10 | url = http://www.iop.org/EJ/article/0004-637X/536/1/185/50113.text.html | doi = 10.1086/308909 | ref = Galama | bibcode=2000ApJ...536..185G|arxiv = astro-ph/9907264 }}
* <cite id = GrootCirc>{{en}}Groot, P. J. ''et al''. (12 March 1997) "[http://www.cbat.eps.harvard.edu/iauc/06500/06584.html IAU Circular 6584: GRB 970228]{{Wayback|url=http://www.cbat.eps.harvard.edu/iauc/06500/06584.html |date=20120318231508 }}". ''International Astronomical Union''.</cite>
* {{en}}{{cite journal | title = Are Gamma-ray Bursts Due to Isotropic Fireballs or Cylindrical Jets? | author = Huang, Yong-feng ''et al''. | journal = Chinese Astronomy and Astrophysics | volume = 26 | issue = 4 | year = 2002 | pages = 414–423 | doi = 10.1016/S0275-1062(02)00092-9 | ref = Huang }}
* <cite id = Hurley>{{en}}Hurley, K. ''et al''. (8 March 1997) "[http://www.mpe.mpg.de/~jcg/grb970228/6578.txt IAU Circular 6578: GRB 970228]{{Wayback|url=http://www.mpe.mpg.de/~jcg/grb970228/6578.txt |date=20110304215240 }}". ''International Astronomical Union''. Retrieved on 23 February 2010.</cite>
* {{en}}{{cite journal | title = Low-Frequency Spectra of Gamma-Ray Bursts | author = Katz, J. I. | journal = Astrophysical Journal | volume = 432 | issue = 2 | pages = L107–L109 | year = 1994 | doi = 10.1086/187523 | ref = Katz | bibcode=1994ApJ...432L.107K|arxiv = astro-ph/9312034 }}
* {{en}}{{cite journal | title = Gamma-Ray Burst Dust Echoes Revisited: Expectations at Early Times | author = Moran, Jane A. and Reichart, Daniel E. | journal = Astrophysical Journal | volume = 632 | issue = 1 | pages = 438–442 | date = 2005-10-10 | doi = 10.1086/432634 | ref = Moran | bibcode=2005ApJ...632..438M|arxiv = astro-ph/0409390 }}
* {{en}}{{cite journal | author = Paczyński, Bohdan and Rhoads, James E. | year = 1993 | title = Radio Transients from Gamma-Ray Bursters | journal = Astrophysical Journal | volume = 418 | pages = L5–L8 | doi = 10.1086/187102 | ref = Pac | bibcode=1993ApJ...418L...5P|arxiv = astro-ph/9307024 }}
* {{en}}{{cite journal | author = Panaitescu, A. | title = Decay phases of Swift X-ray afterglows and the forward-shock model | doi = 10.1098/rsta.2006.1985 | journal = Philosophical Transactions of the Royal Society A | date = 2007-05-15 | volume = 365 | issue =  1854 | pages = 1197–1205 | ref = Panaitescu | pmid = 17293326|bibcode = 2007RSPTA.365.1197P }}
* <cite id = Pedichini>{{en}}Pedichini, F. ''et al''. (22 April 1997) "[http://www.cbat.eps.harvard.edu/iauc/06600/06635.html IAU Circular 6635: GRB 970228; C/1995 O1]{{Wayback|url=http://www.cbat.eps.harvard.edu/iauc/06600/06635.html |date=20120318234211 }}". ''International Astronomical Union''.</cite>
* {{en}}{{cite journal|title=The Redshift of GRB 970508|author=Reichart, Daniel E.|date=1998-02-19|publisher=University of Chicago|journal=Astrophysical Journal Letters|volume=495|issue=2|pages=L99–L101|doi=10.1086/311222|arxiv=astro-ph/9712134 |ref = Reichart98|bibcode=1998ApJ...495L..99R}}
* {{en}}{{cite journal | author = Reichart, Daniel E. | title = GRB 970228 Revisited: Evidence for a Supernova in the Light Curve and Late Spectral Energy Distribution of the Afterglow | journal = Astrophysical Journal | volume = 521 | issue = 2 | pages = L111–L115 | year = 1999 | url = http://www.iop.org/EJ/article/1538-4357/521/2/L111/995411.text.html | doi = 10.1086/312203 | ref = Reichart99 | bibcode=1999ApJ...521L.111R|arxiv = astro-ph/9906079 }}
* {{en}}{{cite journal | author = Reichart, Daniel E. | title = Light Curves and Spectra of Dust Echoes from Gamma-Ray Bursts and Their Afterglows: Continued Evidence That GRB 970228 Is Associated with a Supernova | journal = Astrophysical Journal | volume = 554 | issue = 2 | pages = 649–659 | doi = 10.1086/321428 | year = 2001 | ref = Reichart01 | bibcode=2001ApJ...554..643R|arxiv = astro-ph/0012091 }}
* {{en}}{{cite book| title = Flash! The Hunt for the Biggest Explosions in the Universe | author=Schilling, Govert |publisher=Cambridge University Press | year=2002 | location=Cambridge |url=http://books.google.com/?id=6mGGX6AGBTAC&printsec=frontcover#v=onepage&q&f=false |isbn=0-521-80053-6 |ref = Schilling}}
* {{en}}{{cite journal | title = Spectroscopic Discovery of the Supernova 2003dh Associated with GRB0303291 | first9 = R. | last9 = Schild | first8 = W. R. | last8 = Brown | first7 = P. | last7 = Challis | first6 = N. | last6 = Caldwell | first5 = P. | last5 = Berlind | first4 = P. | last4 = Martini | first3 = P. M. | last3 = Garnavich | first2 = T. | last2 = Matheson | author = Stanek, Krzysztof Z. | journal = Astrophysical Journal | volume = 591 | issue = 1 | pages = L17–L20 | doi = 10.1086/376976 | date = 2003-06-12 |ref = Stanek | bibcode=2003ApJ...591L..17S|arxiv = astro-ph/0304173 }}
* {{en}}{{cite journal|title=Transient optical emission from the error box of the γ-ray burst of 28 February 1997 |url=https://archive.org/details/sim_nature-uk_1997-04-17_386_6626/page/686 | author = van Paradijs, J. ''et al''. | journal = Nature | volume = 386|issue=6626 | year = 1997 | pages = 686–689 | doi = 10.1038/386686a0 |ref = Paradijs | bibcode=1997Natur.386..686V}}
* {{en}}{{cite encyclopedia |title= Gamma-Ray Bursts |encyclopedia=The Universe in Gamma Rays |author=Varendoff, Martin |editor=Volken Schönfelder |publisher=Springer-Verlag |year=2001 |location=Berlin |url=http://books.google.com/?id=pfxoW875a5oC&printsec=frontcover#v=onepage&q&f=false |isbn= 978-3-540-67874-8 |ref=Varendoff}}
* {{en}}{{cite journal | title = Precessing jets interacting with interstellar material as the origin for the light curves of gamma-ray bursts | author = Zwart, Simon F. Portegies and Totani, Tomonori | bibcode = 2001MNRAS.328..951P | journal = Monthly Notices of the Royal Astronomical Society | volume = 328 | pages = 951–957 | date = 2001-08-17 |ref = Zwart | issue = 3 | doi = 10.1046/j.1365-8711.2001.04913.x|arxiv = astro-ph/0006143 }}
{{refend}}

== 外部链接 ==
*[http://www.mpe.mpg.de/~jcg/grb970228.html Gamma-ray Burst 970228]{{Webarchive|url=http://webarchive.loc.gov/all/20090726195702/http://www.mpe.mpg.de/~jcg/grb970228.html |date=2009-07-26 }}{{en}}
*[https://web.archive.org/web/20110303114630/http://www.asdc.asi.it/bepposax/first/grb970228.html BeppoSAX follow-up observations of the region of the Gamma-ray burst GRB 970228]{{en}}

{{DEFAULTSORT:Grb 970228}}

[[Category:1997年发现的天体]]
[[Category:伽玛射线暴|970228]]